continuing from a diversionary thought in another thread...
Generators compatability with computer??????
http://www.busconversions.com/bbs/index.php?topic=18838.0 (http://www.busconversions.com/bbs/index.php?topic=18838.0)
I am a big fan of designing the coach conversion for redundancy, and we have the opportunity for that to extend beyond the coach.
If we are thinking of using the coach as back-up power for the house...
There are neutral ground bonding issues to consider, in order that electrocution hazards are not added to the crisis of lost utility power.
May we have some examples of the conditions that would endanger if the neutral ground is present in both the house and the coach?
What strategies, complex to simple, expensive to inexpensive, might we use to SAFELY accomplish this worthy goal of using our perfectly good generator in the coach to maintain our self-reliant selves inside the bricks and mortar alongside?
happy coaching!
buswarrior
Remember to disconnect the wires from the house so you don't kill the line workers or send power to your neighbors.
A sub panel in the house with no connection to your electric system powered from a "buddy outlet" on the coach would be the safest and simplest solution to my way of thinking.
It could run from the inverter or genset and have a gang of outlets that are readily available for what ever you need to plug in in the house
Properly wired it would be safe and isolated from your normal household power grid
HTH
YMMV
Melbo
Quote from: buswarrior on February 01, 2011, 04:29:02 PM
...
May we have some examples of the conditions that would endanger if the neutral ground is present in both the house and the coach?
In the simplest terms, since the neutral and grounds are connected at both the generator and at the main panel, then the return current will be divided among those pathways between those two points. If you had, say, two #8 wires for ground and neutral, then about half the current will travel on each. But if you use, say, metal clad cable, then a good portion of the return current will actually travel on the jacket. This presents a shock hazard to anyone who comes in contact with the jacket. Since the ground points at both ends are likely interconnected through many means, lots of things can become "hot" this way, including the bus chassis and the house panelboard.
Quote
What strategies, complex to simple, expensive to inexpensive, might we use to SAFELY accomplish this worthy goal of using our perfectly good generator in the coach to maintain our self-reliant selves inside the bricks and mortar alongside?
The most straightforward is what I suggested in the other thread: connect your fridge, computer, etc. directly to the bus power system using extension cords and/or plug strips.
The alternative is to completely isolate the ground from the neutral at one end or the other. In a house, this would mean adding an isolated neutral bus to the main panel, then ensuring that the feeder to this neutral is completely disconnected from the mains (as should also be the hot wires) when feeding from the generator.
Alternatively at the generator end, remove the ground/neutral bonding strap inside the generator's wiring box. However, the generator then must be also physically disconnected from the bus's systems while powering the house, lest there be a potential for a completely unbonded system when finished.
Both of these latter methods involve a level of risk, in that forgetting to put things back the way they ought to be can create an extreme hazard. For this reason, I recommend the simpler extension-cord method, or else buy a proper backup generator for the house.
HTH,
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
Quote from: Melbo on February 01, 2011, 04:43:26 PM
A sub panel in the house with no connection to your electric system powered from a "buddy outlet" on the coach would be the safest and simplest solution to my way of thinking.
It could run from the inverter or genset and have a gang of outlets that are readily available for what ever you need to plug in in the house
Properly wired it would be safe and isolated from your normal household power grid
Such a system is not allowed by code. Any permanently attached/installed electrical panels and receptacles must also be permanently grounded. There are obvious safety risks in having a completely ungrounded electrical distribution system permanently installed.
The only sort of distribution system that is both safe and legal in such a circumstance is one that is "temporary" as that term is defined by the code. Nothing may be permanently affixed or secured in such an installation.
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
I had a friend with local power utility fix mine up I just pull the main and plug bus into welder outlet and all is good. I to was concerned with hurting someone with back feed or mixed up ground. Last time the house was plugged into the bus for 2 weeks.he fixed the main disconnect so it cut hot lines and ground. then house was plugged in like a extension cord.Have used several times and no shocks or back feed to grid.
Quote from: robertglines1 on February 01, 2011, 05:05:57 PM
I had a friend with local power utility fix mine up I just pull the main and plug bus into welder outlet and all is good. I to was concerned with hurting someone with back feed or mixed up ground. Last time the house was plugged into the bus for 2 weeks.he fixed the main disconnect so it cut hot lines and ground. then house was plugged in like a extension cord.Have used several times and no shocks or back feed to grid.
I'm sure you meant to say the disconnect cuts the neutral, not the ground. The ground must never, ever be broken.
That said, I have to say this is incredibly dangerous as well as illegal. On top of the double-bond problem I have already described, backfeeding any system through a female receptacle is never allowed and is, frankly, playing with fire. And should your main disconnect ever be accidentally re-engaged while your generator is connected, you could, indeed, kill someone. At best, you'll overload your generator as it desperately tries to power the whole neighborhood.
Please, folks, let's be smart about this: it is against the law for a reason, and that reason is that people get KILLLED this way.
If you really want to power your house with your bus generator, then fix the double-bond problem and get yourself a proper generator connection with fail-safe transfer mechanism. It's required by law, and, sheesh, they're just not that expensive.
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
In your newer houses, the neutral bar is isolated from your panel and your grounds. That is if they were inspected when built. But you never really know what someone did in your house.
I am with Sean on this one. Use extension cords or a separate generator. You should also install one of these http://www.northerntool.com/shop/tools/product_200196624_200196624# (http://www.northerntool.com/shop/tools/product_200196624_200196624#)
Gary
Quote from: Seayfam on February 01, 2011, 05:43:24 PM
In your newer houses, the neutral bar is isolated from your panel and your grounds. That is if they were inspected when built. But you never really know what someone did in your house.
I would have to go take my panel cover off to be sure, but I recall that the neutral and ground are bonded in my house main panel. My house was built in 2001 per code and was fully inspected. I did all my own wiring with a little help from my father.
Since neutral bonding is suppose to be at a single location, when using my generator to power my house I disconnect the generator from the bus and remove the neutral grounding at the generator. The main circuit breaker on the house panel is turned off and the unbonded generator is back feed into the house panel. Neutral grounding is done in the house panel. Most home panels share the same terminals for both ground and neutral wires making it difficult to isolate neutral to ground bonding. With this configuration the generator is completly disconnected from the bus and neutral bonding is done in the house panel.
When reconnecting the generator to the bus, the neutral bonding at the generator is reconnected. Kenny
Quote from: Seayfam on February 01, 2011, 05:43:24 PM
In your newer houses, the neutral bar is isolated from your panel and your grounds. ...
Actually, in most jurisdictions, the neutral and ground bus will be one and the same in the main panel, even in brand new construction. Sub panels, however, will have a separate, isolated bus for neutrals.
There are some jurisdictions that require an isolated neutral bus in the main panel, with the bond at the service entrance where the meter is located.
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
Other than getting electrocuted, is there a way to test to make sure the system is safe i.e. when the bus generator is separated from the bus and plugged into the house? Can you use a meter to test?
Thanks
Fred
Y'all are really confusing me! ??? I wish Cody were here to help decipher it all out! ;)
;D BK ;D
If any of you have ever faced the fact that you will not have power for many days much less the fact that your business's will not have power for possibly 3 weeks you will soon learn that codes are no longer in play. As with many things in life some common sense takes front and center. I had 4 generators running for several weeks, a fuse panel that only I could understand now and every generator well grounded to the ground besides to the panels at my shop. It was that or no heat, no money and a lot of other serious issues. I back fed my house through the dryer with the generator. Others did it through the heat pump. Breakers work in either direction! You do what you have to do. I did and the biggest hassle was getting fuel to run them when there was no power to the fuel pumps!
In Alaska they have made us isolate the neutrals from the grounds for 15+ years now. I do know that other jurisdictions have different codes. Not only that, even in my state you never know if someone connected a neutral to a ground in a light box someware. This is why I don't recommend connecting the bus to the house, because you just never know.
I am really glad this thread was started, lots of good information. I know a few people here that has been wanting to do this. We have power outages all the time from storms and beetle kill trees falling on lines.
Gary
I think the double bond of the ground and the neutral is less of an issue (as long as both conductors in the bus to house cable are insulated) than the back feeding of a panel via a dryer/welder/hvac outlet and using the main breaker to prevent current flow back to the utility.
The correct way to do it would be a transfer switch before the main house panel.
The ground gets bonded to water and gas services unintentionly many times. If you have an electric water heater it is bonded to the electrical service and also may have a connection to copper water lines. Same thing happens with gas stoves.
I would rather have a double ground to neutral bond than no bond at all, that fault current needs to have a return path to neutral to trip a breaker. Also remember that ground rods provide no function in triping a breaker during a hot to ground fault, it's the ground to neutral bond that handles that.
Not to intentionally add confusion; living out in the country we have a 30KW 230volt generator powered by the PTO on a tractor. I have a panel in the garage that connects directly to the outlet on the generator. The panel back feeds the main house panel via a 30 amp 230volt breaker. We disconnect the Utility Main and fire up the generator. Aside from accidental reconnection of the Utility Main with the generator running, what is the risk of this set up? I do not ground the generator because I assume it is grounded via the neutral-ground bus in the main panel.
Fred
My main concern was hurting the lineman working to restore my power that is why I had Moose a high school class mate and a lineman for the utility fix me up. I know the way he has it fixed it is as if it were sitting on the ground outside house and totally disconnected from bus. It's his life that is in danger. I don't necessarily trust all the fancy auto switch equipment and think it is simple to manually completely disconnect from bus system. Got to keep it simple for me. I still haven't figured the computer out. no chance of feed back if there is no connection at all. won't argue with what it should be by law. More worried about safety. Don't all these automatic switching devices have some control voltage maybe even a half amp that could feed back. Now if we could get all the camp grounds to wire their boxes correctly that would be a milestone. By code they should be- are they?
My concern is someone turning the main on while the generator is still connected and powering the main buss. A lesser concern would be pluging in the generator while the main buss still has power, would smoke the generator but at least it would not kill a lineman.
The link below has interlocks for many panels that will only permit 1 breaker (either main or generator) to be on at the same time. Could save a lineman or your generator.
http://www.interlockkit.com/ (http://www.interlockkit.com/)
Quote from: Fred Mc on February 01, 2011, 06:14:37 PM
Other than getting electrocuted, is there a way to test to make sure the system is safe i.e. when the bus generator is separated from the bus and plugged into the house? Can you use a meter to test?
Yes, but it is not simple.
Once the system is fully connected, but not energized, you can disconnect the neutral feeder from the generator at the panel, then test for continuity between the neutral feeder and the ground. It should read completely open; anything else is dangerous.
Once you have ensured that there is no double-bonding anywhere, reconnect the neutral before energizing the system.
Quote from: Chopper Scott on February 01, 2011, 06:33:50 PM
If any of you have ever faced the fact that you will not have power for many days much less the fact that your business's will not have power for possibly 3 weeks you will soon learn that codes are no longer in play. ...
Sorry, but I do not agree. If someone gets hurt, you will find out very quickly that codes are still very much "in play."
There are safe and legal means of supplying temporary power to structures in emergency situations. Backfeeding a receptacle is not one of them.
If a panel needs to be powered up from a temporary generator it must be physically disconnected from its normal supply and those supply conductors taped and labeled. The temporary connection from the generator must be made at the same location. Merely turning off a disconnect switch or main breaker is not sufficient. It costs nothing but a few minutes of your time and some tape to do this correctly.
And while some breakers may work in both directions (but not all do -- you need to check the specifications) it is not permitted to have the circuit protection for the supply line at its terminus -- circuit protection must be at the originating end.
I will say it again: This sort of shortcut gets people
killed. Saving a few bucks (versus doing it the safe and legal way) to keep your business running or your house warm is not worth anyone's life. Learn the proper and safe methods to connect temporary power and do it right every time -- the life you save may be your own.
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
Quote from: Fredward on February 01, 2011, 07:54:19 PM
... Aside from accidental reconnection of the Utility Main with the generator running, what is the risk of this set up? ...
I would suggest that accidental reconnection would be enough risk to avoid doing this.
But since you asked: There is a reasonable expectation that the main disconnect will cut all power to the panel, and now you have bypassed it in a non-visible, non-obvious way. Anyone needing to quickly cut power to that panel now has no way to do it, or at least it is not apparent how to do it. That might include firefighters, paramedics, and other rescuers responding to a situation at your location.
This is precisely the reason that temporary feeds must be immediately recognizable and obvious (as I wrote above), and why permanent transfer arrangements must be clear. Multiply-fed panels must be so labeled with a clear indication of how to remove all sources feeding them.
Again, it is straightforward to do this right with just a little bit of effort and some extra parts. Adding a manual transfer switch or an interlocking breaker arrangement such as the one suggested earlier in this thread would make your installation safe and compliant.
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
This is a very interesting thread.
We have one of these installed next to our main breaker box in the basement of the house. Generator Panel (http://products.schneider-electric.us/products-services/products/load-centers/backup-power-connection/qo-generator-panels/). It is supposed to be used by plugging a generator into the male 3-prong plug. I think you are supposed to flip the switch before plugging it in. Then we have 4 breakers on it, on the right side of the panel, one for the furnace, one for some outlets, one for some lights, etc. So we would then have power to that area of the house to live in during a storm. The generator is to be outside, and the plug for it is on the outside of the house. We have never used it to the best of my knowledge. This was installed by a professional electrician and inspected by a state inspector.
I think the key to this discussion is to disconnect the bus from the generator? Since I don't have a bus, I obviously am having trouble visualizing how to do this, or what it actually does. If the gen is disconnected from the bus, then the gen is identical to one sitting on the garage floor or the ground next to the house.
Thanks for helping those of us who are electrically challenged.
Mike
P.S. Sean, per your recommendation from Arcadia, I have been working slowly through a basic electricity book in an attempt to better understand your writings. I still have a long way to go. Thank you.
After all the bull so far Robert is right and the easiest have an electrician pull a large remote off the main panel with a welding plug . You have to make sure the main breakers are tripped before pluging in the gen. cord. Use the KISS system
We had an ice storm here last January and someone back feed from their generator to their home and an electric company employee that came here to help the local electric company from Ocala Florida was electrocuted because of this. HAVE A CERTIFIED ELECTRICAN DO THIS AND YOU MAY JUST SAVE A LIFE.
I did this the easy, but expensive, way. I installed a permanent standby generator when my house was built. I have an automatic transfer switch and a seperate subpanel in the house for stuff powered by the generator. I went to all this expense and only two power outages in 9 years. I pump a ton of water out of my basement and I didn't want a flooded basement with no power.
My generator does burn natural gas. I figure if we have a disaster that knocks out both natural gas and electric I will have bigger things to worry about than electricity for my house. I would still have the option of running extension cords to my bus generator.
I did not have an RV with a generator when I installed the standby generator.
That's why I stated that my breaker panel was one that only I understood Sean. There was no chance of backfeeding into the main power system. I am sure it wouldn't meet codes. I thought we were talking about grounds?
I was wondering when someone would mention the right way to do this. There are easily available and not all that stupidly expensive automatic transfer switches designed to do exactly what is being discussed - connect a generator to a house for emergency power. In the big picture, not all that much fuss.
In my current house, I put the generator on the porch or the back deck, and run a big extension cord in through the basement window. I plug in whatever I need at the time. My new house is farther out in the country, and has a manual setup for generators. Professionally installed but I am almost positive there are code issues with it. One of my first jobs when i get out there this summer is to trace it all out,, figure out what the electrician did, and get a licensed electrician in to fix it.
Brian
My solution is easy, fire up the generator live in the bus until power is back on!
It sits on a concrete pad beside shop full hook up to water and sewer,heat and air, empty out house frig if needed.
Problem solved!! ;D ;D
ED
I continue to amazed at how three simple wires and a ground can be so confusing, especially ground and neutral bonding.
I have to say that this very subject is very timely, something ive intended to figure out before now. But after reading all this I see just how little I know about the subject and that I need more study.
Now that the smoke has settled and everyone has given their thoughts, I'll give my last thoughts.
I have wired approximately 50 houses and I come from a family of electricians, my oldest boy is going through the (IBEW) as we speak. However I am new on this board, so nobody should take my word for anything. Butt "Sean" is our residential electrician here... He is not going to steer any of us in the wrong direction!!
I myself and probably Sean could never live with the idea of telling someone to do something that is illegal and unsafe. If something ever happened, It would be on us.
There is a LEGAL AND SAFE way of doing this. And there is many other ways of doing this, that is quick and will work, but illegal and potentially deadly.
I do have one disagreement on one thing, If you have a house that has the neutrals and the grounds bonded in the panel. Isolating those neutrals at the panel isn't fullproof.
My experiences are...if a panel has been bonded, then chances are light boxes and switch boxes also have been bonded.
Just my thoughts. ;)
Gary
Quote from: Seayfam on February 02, 2011, 11:07:37 AM...There is a LEGAL AND SAFE way of doing this...
And more to the point "published (http://www.nfpa.org/catalog/product.asp?title=Code-70-2008-National-Electrical-Code-NEC-Handbook&category%5Fname=2008+National+Electrical+Code+%28NEC%29&pid=70HB08&target%5Fpid=70HB08&src%5Fpid=&link%5Ftype=category)"...
Article 250 Grounding and Bonding
Article 445 Generators
Article 551 Recreational Vehicles and Recreational Vehicle Parks
Almost all of Chapter 7 but at least:
Article 700 Emergency Systems
Article 702 Optional Standby Systems
Article 705 Interconnected Electric Power Production Sources
And this too (http://www.nfpa.org/catalog/product.asp?title=Code-1192-2011-Recreational-Vehicles&category%5Fname=&pid=119211&target%5Fpid=119211&src%5Fpid=&link%5Ftype=search)...
-T
My name is Jim and I am at this meeting because I need help. ;D :o
You guys really got my attention! Yes, I made up what has been called a "suicide cable" (male/male) on another board (yes, you guys got me doing some research). I plugged it into a 50 amp dongle on the bus and a welder outlet in the shop. Opened the main breakers first. Obviously it worked and I did not die (nor anyone else).
I tried to research transfer switches for the house end, but it looks like you would have to rewire a good part of your house. In my case, I have two service boxes (one outside for big circuits and one in the kitchen area for the small circuits - outlets and lights). Would just not be practical to try to accommodate a transfer switch.
In a like manner, running extension cords from the shop to the house is not practical, as it is well over 50 feet to many things I would need to power. Plus I need 220 for the well.
So, here is my plan - let me know what you think:
1) I will buy a small service box with perhaps room for 6 breakers. The feed for that box will be a 50 amp male flexible cord about 10 feet long.
2) When I did the wiring to my shop, I ran a second set of 100 amp service wires to the shop. One end is in the main house service box (not hooked up) and the other end is in the shop, also not hooked up.
3) The end in the main service box will be hooked up to a 50 amp outlet mounted just below the main service box in the proper enclosure.
4) I will put a 50 amp connector (male) on the shop end. This end will be plugged into a 50 amp extension cord from the bus.
5) From the new service box, I will drop a 220 outlet for the well pump and two or three 120V outlets (all mounted below the box). The new service box and outlets will be in the furnace room where the well pump service, furnace, and freezer are located.
6) I will put outlet boxes and plugs in the normal circuits for the furnace and well pump, so that I can unplug them from the normal service and plug them into the new service panel/outlets.
7) I will make up, or buy, heavy duty extension cords to run upstairs where I will hook up a couple of lights and the fridge.
8) When I need to hook everything up I will plug the shop end into the RV extension cord, plug the new service panel into the 50 amp outlet at the main service box (the one connected to the RV) and then plug in the furnace, well, freezer and extension cords at the outlets from the new service panel.
9) This system will completely separate the generator from any public power supply. I will ground the service panel. The only issue that I can think of is the bonding at the generator. I don't think that will be an issue, but need input.
If you think about it, this is just a fancy set of extension cords, but executed a bit better for my needs.
BTW, my generator is 10 KW wired for 220. Thus I only have 40A 220V available, but that seems to be OK for what I need to run. This scheme will also let me balance the load fairly well. The output from the generator is connected to 40 amp breakers, so the system should be well protected.
Thanks for looking at my scheme.
Jim
Jim, could you fit another breaker in your main box outside for the generator feed from the shop. You could then interlock the utility main with the generator breaker with a kit from the link below. This would power up the entire service and your kitchen panel that I assume is a sub panel of the main box outside.
You would have to shed some of the large loads in the outside panel, A/C units, electric water heaters etc.
http://www.interlockkit.com/ (http://www.interlockkit.com/)
I am assuming they make a kit for your existing outside box, this setup will assure that the main has to be open before you could close the generator backfeed breaker
I like what Kevin said.
Also, if you only have a few "emergency loads" and no space left in your box (common), you can move a few circuits to a main-lug sub-panel and place this device between the main panel and the sub-panel (http://www.northerntool.com/shop/tools/product_200196574_200196574?cm_ven=natural&cm_cat=netconcepts&cm_pla=Google&cm_ite=generator%2Btransfer%2Bbox). This should also save you some wiring duplication, and reduce the marking complexity (you need to indicate where a back-up powered circuit gets its power). If you don't have a direct line of sight to the generator, some type of pilot light would be a good idea to show that the gen input is live.
This seems like a perfect topic covered by NEC Articles 700, 702, and 705...
I don't get what's so complicated with AC power - it seems fairly straight-forward.
Although, I do believe the details get more complicated if the generator has its own Ground (as it should, 10-foot or longer by 3/4" 12-mil copper-clad steel-rod driven down to the water table), and the Neutral is correctly bonded at the generator (should be). Sean can check me on this, but I recall that Neutral must be bonded to Ground at the point of service entry for a typical residence (mostly because you need to provide ground locally at the site and null out the Neutral line from the transformer - the power company doesn't supply a ground from the pole, all GFCI devices should be downstream from the bonding point). If you don't isolate the Neutral at the main breaker when you power the generator input, both the ground and Neutral will split the Neutral return power and this will pop a generator's GFCI (as it should. GFCI looks for balance in the Hot an Neutral - any difference is presumed lost to Ground, no current should be "missing" - just 10mA can kill a person). This means that you would need to separate both Hot-legs of the main input plus the Neutral - but leave Ground from the main connected (it should never be isolated!!). Remember that the Ground-wire and the enclosure and conduit bonding is there to catch stray current and bring it back to a point where it can be properly controlled (i.e. GFCI) - incorrectly isolating the Ground can lead to a person or some other potentially damagable item completing the ground circuit otherwise - the worst being a person working on a system and touching both open ends of a circuit with different/separate hands causing the current to cross the chest cavity.
This same thing is done in Inverters with a Generator input - the individual power source devices have the Neutral bonded to Ground at the earliest point. When a generator input powers the inverter, it must isolate the Neutral or GFCIs pop (current incorrectly carried by ground).
-T
Kevin and Tim, neat concept.
QuoteI don't get what's so complicated with AC power - it seems fairly straight-forward.
Tim, if you have ever seen a mechanical engineering student in an EE lab, you would not make that statement.
If I understand the concept, if the supply breaker from the generator is on, the InterLock demands that the main breaker is off via the steel plate.
I assume that I would tie the neutral and ground from the generator to the bars in the main breaker box.
Early in this thread, it sounded like using the main breakers to isolate the house from the grid was a no-no. Apparently if there is a mechanical lock system then using these breakers is acceptable. It is minus 10 degrees tonight, so I will wait until tomorrow to look. I am pretty sure I have an extra slot.
On another board, someone mentioned that the neutral was still tied to the grid and that could cause a problem. Comments?
I am still a little lost of the bonding issue. Seems to me that the InterLock does not resolve that problem. Tim, it sounds like you are saying that if you provide a good earth ground to the generator, then the bonding is not an issue.
You guys are slowly getting this EE challenged ME up to speed. ;D
A quick question for the experts, Tim says a copper clad steel rod driven down to the water table, is that correct? I just asked cody how deep the water table is here and he didn't know so he called Larson Well drilling and asked bob larson, bob said generally 25 to 60 foot deep, thats a heck of a rod, was something else meant?
Quote from: rv_safetyman on February 02, 2011, 05:30:23 PM
...
9) This system will completely separate the generator from any public power supply. I will ground the service panel. The only issue that I can think of is the bonding at the generator. I don't think that will be an issue, but need input.
...
Well, now we are back to the original question that started this thread. Everything you propose here will work, so long as the neutral in your new sub-panel is isolated from the ground. When you connect this sub-panel to your coach generator, the neutral and ground will be bonded then only at the generator, which is as it should be.
I would not worry about additional grounding, such as a driven rod, for the generator so long as there is a good ground connection at the new sub-panel.
Quote from: rv_safetyman on February 02, 2011, 08:27:30 PM
...
I assume that I would tie the neutral and ground from the generator to the bars in the main breaker box.
Early in this thread, it sounded like using the main breakers to isolate the house from the grid was a no-no. Apparently if there is a mechanical lock system then using these breakers is acceptable. ...
On another board, someone mentioned that the neutral was still tied to the grid and that could cause a problem.
The neutrals must be isolated from one another, otherwise you will suffer the multiple-bonding issue that can be an extreme hazard.
Interlocking breakers are a legitimate means to separate the services, but you must use multi-pole breakers and use one pole for the neutral. That means a two-pole breaker for a 120-volt service, or a three-pole breaker for a 120/240-volt service.
Quote
I am still a little lost of the bonding issue. Seems to me that the InterLock does not resolve that problem. Tim, it sounds like you are saying that if you provide a good earth ground to the generator, then the bonding is not an issue.
Yes, the bonding is still an issue, no matter how many driven grounds you have. As I just wrote, an interlocking breaker system is only acceptable for this purpose if the neutrals are also interlocked. I probably should have made that clear earlier in the thread when I agreed that such an interlock is acceptable.
Quote from: libby on February 02, 2011, 08:36:42 PM
... Tim says a copper clad steel rod driven down to the water table, is that correct? ...
I've never heard this particular recommendation before. Driven ground rods are generally 8' long and driven in a minimum of 6'. It is important to get them below the frost line for best conductivity.
That said, again I do not see the need for an additional driven ground in anything we've been discussing. Once the grounded case of the generator has been connected to the existing driven rod that is already part of the house's electrical system via the generator umbilical, the grounding requirement has been met.
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
So in a standard 200 amp house main panel does the main disconnect (which is 240v) shut off the hot and neutral when it is shut off? How can you tell if it disconnects the hot and neutral?
Thanks
Fred
Quote from: Fred Mc on February 03, 2011, 09:00:44 AM
So in a standard 200 amp house main panel does the main disconnect (which is 240v) shut off the hot and neutral when it is shut off? How can you tell if it disconnects the hot and neutral?
Thanks
Fred
No it doesn't, it just shuts off the two hots. Even the main breaker at the meter loop only disconnects the two hots.
Gary
A standard house panel has a two pole main breaker which interrupts the two 120 volt feeds only. It does not interrupt ground or neutral. In a standard house main panel neutral and ground are bonded in the panel itself. That should be the only bond for the house.
My understanding of the way a generator panel works is - you have a separate panel from the main house panel, that supplies a subset of the house (could be all of the house, but usually a subset of important branches is selected to run from the Generator). that panel has no bond between neutral and ground. It is connected back the main panel AND to the generator by interconnected breakers that connect both 120 volt live feeds and neutral from whichever supply is in use at the time. the generator panel gets both it's supply and it's neutral bond from it's source, be that the main panel or the generator. It does share the common ground at all times. The Interconnected breakers must be physically unable to connect both supply choices at once, and must always connect all the feeds to the selected supply - all of the two live feeds and the ground simultaneously. It can be a manual or automatic switch system
Now - I wrote all that out to see if I actually got it. Did I?
Brian
Being a believer in Murphy; I had a large knife switch installed years ago. The house is connected to the common with the power company on one side and the generator on the other; power company and the generator can't be connected. No failed breakers to cross-connect, no systems to remember to have in the right configuration, just move the switch from power company to generator. Since my generator is not big enough (at this time) to run the whole house, I have to switch a couple of breakers to manage the load. Worst case if I forget is a tripped breaker on the generator.
Still very confusing to me. Most commercially available generator transfer switches do not switch the power company neutral.
An open neutral is an absolute disaster in a house, causing all manner of equipment damage, possible fire and shock hazard. The increased risk of an open neutral by introducing a breaker or switch into the mix seems risky to me. If there were such a switch, I would want to be very sure that it made the neutral before making the hots.
I have seen it happen where the kitchen stove, refrigerator, and several televisions, along with multiple small lamps and appliances were destroyed by an open neutral. Fortunately, the power company accepted responsibility and paid for everything.
There is no way to be sure that the neutral coming into the house is not grounded. You can add an isolated neutral bar in your panel but it still might be grounded at your neighbors house if you share a transformer.
there is no neutral coming into my house. I went outside and looked :) there are only two hot leads coming from the street. Neutral is created by bonding to ground within the main panel, only. No need to switch "power company neutral" since it doesn't exist.
for me, at my house, anyway.
edit - I went outside and looked again, the bare wire is indeed brought into the meter base. Not for nothing do i hire electricians to do this stuff for me.
Brian
So just to be sure, I built an interlock device similar to the one referred to previously.(http://www.interlockkit.com/ (http://www.interlockkit.com/)) which PHYSICALLY prevents you from having both the main breaker and the breaker receiving power from the generator on at the same time. With the main breaker shut off is that a failsafe way of assuring that you won't get backfeeding into the utilities lines? I guess to be doubly sure you could remove the meter head but the utility might just frown on that. ;D
Thanks
Fred
Brian
Are the 2 hots wraped (suspended) by a bare wire, the bare wire is the utility neutral. Unless you have a 30 or 60 amp 120V service there has to be a utility neutral. Looking back at your post you said 2 hots so you must have a 240V service and that must have a utility neutral.
Jim
How does your gennerator connect to the bus electrical system now, is it direct wired to the circuit breaker panel or is it cord and plug connected and is it a 4 wire plug? If it is cord and plug you may be able to remove the generator bond and replace it with a bond in the circuit breaker panel. Then when you unplug the generator from the bus and plug the cord to your house in the bond will be at the house panel. You would only have 1 bond that way and it should be code legal.
I still think we are making more of the double bonding issue then we should, worse thing that can happen is you have a paralel path where both conductors will carry part of the neutral current. Since both conductors are sized to handle full load I do not see the hazard. I see more kill potential in not having the main/generator breaker interlock.
If you have a copper city water service in your house take an ampmeter reading on that conductor. Bet you find several amps flowing on the water main, thats the utility and some of your neghibors geting their neutral thru your water main ground. Water guys around here put a jumper cable across the water meter before they remove it so they do not get shocked. New installations require the jumper by code so even the code expects some form of extra bonding.
Let me try and explain how wiring is done in Alaska by code. I personally think every state should be done the same.
The power company brings in 4/0-4/0-2/0 to the meter loop mounted on your house or shop. The two 4/0 are hot and the 2/0 is neutral. In your meter loop you have two bars that your 200a breaker connects to. You also have a neutral bar that the 2/0 wire connects to. At that neutral bar you run a #6 bare ground wire to 2ea 5/8 x 8 ground rods drove in 6' apart, and you loop your ground wire, from the first rod to the second rod and back to the first rod. "This keeps your neighbors low voltage neutral from entering your house"
Inside the house the breaker panel can have another 200a breaker in there, but not required. You have a isolated neutral bar, you have a ground bar and your two hots. From your ground bar, you run another #6 bare ground wire to either a good plumbing or gas ground, or you add another ground rod set up. Then your neutral goes back out to your meter and is grounded there. This prevents any low voltage from any of your appliances to be connected to your grounds in your house. Otherwise why have a ground lug on any of your outlets.
If you are not set up this way then you can get shocked by touching any metal appliance or light fixture in your house. Also could be bad on your computers.
Hopefully this explains the neutral bonding issue for anybody that may be confused.
Gary
Just read something that joged my memory
Less than 10 years ago electric dryers and stoves used to be wired with 2 hots and a neutral, the neutral was allowed to be bonded to the appliance case and serve as a ground. If you buy a new appliance today they still provide instructions on how to connect it to a 3 wire cord.
In the 3 wire setup you have the potental a shock hazard if the neutral becomes open as the appliance case could become live.
I do not see that happening in a multiple bond like we have been discussing. Just some electrical trivia.
Quote from: Sean on February 03, 2011, 06:24:48 AMQuote from: libby on February 02, 2011, 08:36:42 PM... Tim says a copper clad steel rod driven down to the water table, is that correct?...
I've never heard this particular recommendation before. Driven ground rods are generally 8' long and driven in a minimum of 6'. It is important to get them below the frost line for best conductivity.
That said, again I do not see the need for an additional driven ground in anything we've been discussing. Once the grounded case of the generator has been connected to the existing driven rod that is already part of the house's electrical system via the generator umbilical, the grounding requirement has been met.
If you already have a sufficient Ground, you shouldn't need to add a ground for the generator - yes, I agree with Sean.
NEC Chapter 2, Article 250.34 deals with Vehicle mounted generator grounding.
NEC Chapter 2, Article 250.52 deal with the ground electrode itself - it is not a full explanation of the concept, just enough to be generally "safe".
A better explanation of grounding and rods is available in NFPA 780 (http://www.nfpa.org/catalog/product.asp?pid=78011&order%5Fsrc=B484), IEEE-142 (http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F4396961%2F4396962%2F04396963.pdf%3Farnumber%3D4396963&authDecision=-203), MIL-HDBK-419A, and MIL-STD-188-124B (updated to Note 3 - the physical spec I quoted for the ground rod is in this guy in section 5.1.1.1.4).
The IEEE stuff is not free just like NFPA's stuff, but the MIL info can be found for free (unclassified) at this site: https://assist.daps.dla.mil/quicksearch/ (https://assist.daps.dla.mil/quicksearch/)
-T
Quote from: Len Silva on February 03, 2011, 10:09:49 AM
Still very confusing to me. Most commercially available generator transfer switches do not switch the power company neutral.
That's because if you use the proper generator, no neutral transfer is required. See my original post on this topic.
The reason the neutral must be transferred in the case of using a generator built into a bus is that there is a ground-neutral bond in the bus. Along with the one already inside your house, you now have a double-bond situation.
This means that current will be flowing on the ground system, which you never want.
So, again, to be clear: If you are using a household backup generator, properly configured and installed, then a normal household transfer switch is OK.
If you are using your bus to power your house, you need a switch that also transfers the neutrals.
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
I think to further clarify what Sean is saying about the Neutral/ground bonding issue (not that it really needs clarification, but anyway): An rv generator has the ground and neutral "bonded", or "connected together" at the generator itself. a household standby generator has the neutral and grounds "isolated" or "not connected together". this is why a transfer switch for a standby generator in a house or other type of permanent structure does not transfer or switch over the neutral feeds...no reason to. every source of power must have a neutral to ground bond. in permanent structures like your house it is accomplished at the point of connection, usually the main breaker panel. mobile homes can be an exception. mobile homes usually require the meter to be mounted on a remote pedastal, and the main breaker panel inside the home. In this case the neutral/ground bond is accomplished at the remote meter pedestal, and the main breaker panel in the mobile home has seperate neutral and ground bars. there is still only one neutral/ground bond in the entire system. in an rv when plugged into shore power, the neutral/ground bond is accomplished at the source of the power supply...the main breaker panel at the house. still only one neutral to ground bond. when running the rv generator to power the rv, the neutral to ground bond is accomplished at the generator. next is where we differ between rv's and permanent structures..... any proper rv transfer switch also transfers the neutral line. by doing so we still have only one point that the ground and neutral are bonded together.
If you are trying to power a mobile home as described above from an rv generator the setup would be fairly simple to achieve.
Sean, any reason why a 3 pole transfer switch couldn't be used right before the main panel to accomplish this? by isolating the neutral and ground in the main panel and placing the bond at the shore side (utility supply) of the transfer switch? would that be a code violation? if not that would seem to be a simple way of solving the multiple bonding issue, and ensuring that 2 power sources are never able to be cross connected.
Kevin, you asked how my generator is wired in the bus. As best as I recall, I bring the 4 wires out of the generator and have the hots connected to 40 A breakers. I then run the circuit to the transfer box. I will have to check to see where I connected the 50 amp cord (for the auxiliary power supply).
I did not get out to the main power panel to see if I have space for an extra breaker.
Jim
I have a quick question for Sean
I just need to clear one thing up on a code issue I have. Are you considering the main panel, the distribution panel in the house that all the breakers are in? Or are you considering the main panel, at the service entrance on the outside of the house? This is where most of our main breakers are at. That way if there is a fire, the firefighters can cut the power before going inside. From everything I can gather, most of your main breakers are inside in the same panel as all the other breakers. And there is no main outside at the meter.
I just need to clear this up so I know where all the neutrals and grounds are bonding in your area.
Thanks
Gary
DING DING DING!!!
Quote:
.... you now have a double-bond situation.
This means that current will be flowing on the ground system, which you never want.
What happens if power is able to flow on the ground system, to more than one destination?
The power has a choice of routing, and a choice of destinations, which is quite dangerous.
All the places where the neutral and ground are connected together become destinations.
Having the ground and neutral connected together in more than one place creates the conditions which may allow power to flow in all the metal that we thought was safely grounded... pipes, the metal case of tools and appliances, the electric boxes, and outside, the body of the coach.
With the ground and neutral connected together in more than one place, the power has a choice of more than one destination, and paths that we have assumed were not possible, or at least, we assumed were safe routes for the power to take, become possible.
Picture the family dog in the middle of a field, with the family around the perimeter. Everyone call the dog... will the dog go to the same person every time? Can we predict the dog's path? (forgetting for the moment the bias to go to whoever feeds it!)
Now, if the dog was in the middle of the field and only one family member was present and called the dog, the dog has only one choice of destination.
We only want one destination for the power.
The safety message is:
A person could become a better path for that power to follow, a short-cut of sorts, an easier path for the power than staying in the wires and metal and going back via the "proper" or expected, route, if that person was to be touching the wrong combination of things.
Becoming the path for power to return is electrocution.
How about some plausible examples of how we might get electrocuted with more than one neutral/ground connection?
happy coaching!
buswarrior
Typically, unless it is connected to shore power, the bus itself is not grounded, as it is sitting on rubber tires.
Even with all the precautions you might take with this connection, I think I would run a large (maybe 2/0) cable directly from the house ground to the bus frame, even directly to the generator frame.
Quote from: thomasinnv on February 03, 2011, 05:10:31 PM
...
Sean, any reason why a 3 pole transfer switch couldn't be used right before the main panel to accomplish this?
...
That is actually the preferred solution. However, it does no good to install a 3-pole switch ahead of the main panel unless you first ensure that the neutrals in the main panel are isolated.
Depending on how the house was originally wired, the ground/neutral bonding point may be in this main panel, and when it is, it is common for electricians to simply use the same bus bar for both the grounds and neutrals for all the branch circuits.
In such an arrangement, it can be a challenge to re-wire the panel with separate, isolated bus bars.
Quote from: Seayfam on February 03, 2011, 11:58:06 PM
I have a quick question for Sean
I just need to clear one thing up on a code issue I have. Are you considering the main panel, the distribution panel in the house that all the breakers are in? Or are you considering the main panel, at the service entrance on the outside of the house? This is where most of our main breakers are at. ...
By definition, a main panel is the first panel after the transformer. Any panels downstream of that are considered sub-panels.
As you note, some builders put (and some jurisdictions require) the main panel outside at the service entrance, sometimes in the same enclosure as the meter. Special partitioned enclosures are used for this where the meter part of the panel can be sealed by the power company, but the breaker portion is customer-accessible.
With such an arrangement, the neutral-ground bond is likely inside this panel. The panel inside your house, which is fed from a breaker in this outside panel, is technically a sub-panel. If properly installed, this sub-panel will have an isolated neutral bus.
Note that the neutral-ground bond may not be in a breaker panel at all -- depending on power company, local codes, and builder practices, it might be in the meter enclosure at the service entrance, or even at the transformer. In this case, all panels downstream of the bond location will have isolated neutral bars.
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
Thanks
That solved all the issues I was having. I do know a lot of people that have a main breaker inside and they consider it the main panel, when infact they have one out at the meter. Hopefully this cleared things up for others with the same situation.
Gary
I would have to say that on long island 99.9% of services have a main breaker inside at the panel, this breaker is the service disconnect and the bonding takes place in this panel.
The other .1% that have outside breakers (either part of the meter or hung under the meter) are wired that way because the NEC limits the length of unfused service conductors that can be run inside the structure before they hit the main breaker.
The length of the unfused conductors is up to the inspector, most around here allow 4 to 5 feet as the maximum inside. The bonding takes place at the outside breaker and you have to treat the inside panel as a subpanel. That means runing 4 conductors (2 hot-1 neutral-1 ground) between the outside and inside panels. There is no bonding done on the inside panel and the neutral and ground land on their own connection bars
This does get confusing, seems many have lil bit different ideas to accomplish the same thing.
If im understanding this properly.....
The main line (from pole/meter) neutral is grounded (bonded) at the service panel/main breaker. IE; all circuit grounds and neutrals return to the main panel and are bonded, generally with a bonding screw that connects the neutral and ground BUS bars.
Sub panels are NOT bonded, all circuit grounds tied to the sub panel ground BUS return to the main panel via seperate ground wire, and additionally, sub panels may have ground rods connected to the sub panel ground BUS bar.
A transfer switch generally only switches HOTS, not neutrals. Neutrals pass through, no bonding of neutral to ground?
A home generator is NOT bonded.
An RV generator IS bonded.
To then connect an RV generator to your home/transfer switch, should you then UN BOND the generator?? Would it then be ideal to run a 4 wire 50 amp type plug, or three wire 30 amp with a seperate ground wire to the house/transfer switch connection?
One must be careful in saying that a home generator is NOT bonded.
A home generator could be a generator that was designed solely for the purpose of residential power backup in which case it is likely to to NOT have a Neutral Bond.
A home generator could be construed as a portable general purpose generator which is likely TO have a Neutral Bond that needs to be unbonded when using it as a residential power backup.
There is no rule of thumb here - You should check the generator you are about to use for residential backup to insure the neutral is NOT bonded..... The bonding is done in the residential Main power panel only
QuoteHow about some plausible examples of how we might get electrocuted with more than one neutral/ground connection?
Lots of ways... #1 for me would be the distribution panel (breaker panel in your house could become HOT)
Gary
Quote from: buswarrior on February 04, 2011, 07:09:10 AM
...The safety message is:
A person could become a better path for that power to follow, a shortcut of sorts, an easier path for the power than staying in the wires and metal and going back via the "proper" or expected, route, if that person was to be touching the wrong combination of things...
It's not actually that simple - yes, the path of least resistance is where most of the power will go, but power will split its power even to a poor conductor (so long as it's good enough).
When you have parallel paths for power, the resistances are fractionally additive,
R
total = 1 / ( (1/R
first-conductor) + (1/R
second-conductor) + .... + (1/R
nth-conductor) )
but the voltage across all of the resistances are EQUAL (this means if you hook yourself up as a parallel conductor where the potential between both connection points is 120VAC, you will get 120VAC at your fingers). How much current you carry is determined by how much resistance you present to a circuit. If a ground wire and neutral wire are 10mili-Ohms each end to end, and you are 1MegOhms - the neutral and ground for 120V will conduct up to roughly 12,000-Amps - but you can conduct up to 0.1mili-Amps. More likely you have a lower resistance like 3,000 Ohms to 4,000 Ohms (source Wikipedia "electrocution" Article (http://en.wikipedia.org/wiki/Electric_shock#Pathophysiology)) - in which case you can conduct up to 30mili-Amps, or three times as much current as is needed to kill a person. Obviously, the conditions will vary infinitely/daily but this should illustrate the importance of ensuring that the ground only carries current to trip fault devices - it should not become a parallel circuit load conductor.
Quote from: buswarrior on February 04, 2011, 07:09:10 AM
...How about some plausible examples of how we might get electrocuted with more than one neutral/ground connection?...
Quote from: Len Silva on February 04, 2011, 07:18:48 AM...typically, unless it is connected to shore power, the bus itself is not grounded, as it is sitting on rubber tires.
The bus my not be grounded to earth - but the
CHASSIS is bonded to ground!! The rubber tire thing only keeps you safe so long as you or someone you care about doesn't hold onto a metal handrail or latch handle at the door, and step into or out of your bus at 0-dark-thirty with slippers onto moist or snow covered ground... then if you are double bonded, the person gives the current yet another path and
ZAP.
-Tim
To make it more simple ::) each and EVERY neutral/ground bond should have only one bond at the source - any configuration which violates this rule downstream of the source invites disaster - FWIW
Quote from: Tim Strommen on February 04, 2011, 01:27:28 PM
The rubber tire thing only keeps you safe so long as you or someone you care about doesn't hold onto a metal handrail or latch handle at the door, and step into or out of your bus at 0-dark-thirty with slippers onto moist or snow covered ground... then if you are double bonded, the person gives the current yet another path and ZAP.
-Tim
So im still a bit confused here. The RV generator is bonded at the Gen to take the grounds back to the source so you wont get shocked stepping onto the ground. When you plug into shore power, your grounds are tied to the main panel in the house/campground, so you wont get shocked stepping onto the ground. I get all that.
When your using the gen to power you house, do you want the gen bonded, or un bonded?
From reading this, it would appear the answer is yes or no, that we need to "check" the grounds? It would also appear that many of us have put much greater reliance on campgrounds to assure we are properly grounded than is warranted.
The ground is supposed to TRIP the breaker when there is a fault not provide safety
HTH
Melbo
Quote from: artvonne on February 05, 2011, 08:28:22 AM
...
When your using the gen to power you house, do you want the gen bonded, or un bonded?
...
Ideally, you want the ground and neutral bonded in the generator, which is the source in this case, and the neutrals isolated from the ground in the panel being powered inside the house.
Quote from: Melbo on February 05, 2011, 11:59:30 AM
The ground is supposed to TRIP the breaker when there is a fault not provide safety
This is only partially correct -- ONE of the purposes of a safety ground is to conduct fault current back to the neutral, closing the circuit and thus tripping the breaker. Note that this only works if the ground and neutral are, indeed, bonded someplace.
However the safety ground system has several additional purposes. For one it ensures that any accessible conductive components of an appliance are at the same potential as the earth, so that an appliance user can not experience a shock. This is one reason a driven ground, connected to the earth, is required. If the only purpose of a safety ground was to conduct fault current back to the neutral to trip the breaker, no such driven ground would be needed.
The safety ground system also conducts dangerous voltage originating from elsewhere safely to earth, minimizing the potential for equipment damage or persons being shocked. For example, a lightning strike, or an arc or direct contact from a high-voltage source such as a power line. Even an electrostatic buildup will be safely drained to earth by a proper safety ground system.
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
Quote from: Sean on February 05, 2011, 09:01:01 PM
Ideally, you want the ground and neutral bonded in the generator, which is the source in this case, and the neutrals isolated from the ground in the panel being powered inside the house.
Are you saying to "remove" the bonding screw inside the house main panel, (unbonding the neutral from ground) when using an RV to generate power to your house?
I have a 200a transfer switch that only switches the hots. If I used the RV to power the transfer switch, and the generator in the RV is bonded, how would you suggest grounding/bonding the transfer switch?
I was reading something written back in the early days of electricity and some of the controversy about added grounds. Someone said something about bringing the ground up to to all the circuits and appliances puts half the power that can kill you in your hands.
Artvonne
Go out to your meterloop and see if you have a main breaker in a unlocked panel next to the meter. Or look for a main disconnect at the service entrance. If you have a main out there, look inside the panel and see if there is a bond from neutral to a ground rod. "If a breaker is out side NEC says bond there"
If there is a bond there, then you can isolate your neutrals in your distribution panel in the house. Also make sure the distribution panel is grounded. "This method has been code for 15+ years here"
Now if you are set up this way, you can install your 200A 3wire transfer switch in line before your breaker panel. Also you can leave the generator bonded. "Using your RV"
Now if you don't have a main disconnect outside, or in it's own panel, and the only main is with all your breakers. "Don't isolate them" And if you ask me, I'll tell you to run extension cords from your bus. Or a separate panel isolated from the power company as RVsaftyman is wanting to do.
I hope this has cleared it all up for you!! :)
Gary
Interesting reading and fairly easy to understand.....
http://members.rennlist.org/warren/generator.html (http://members.rennlist.org/warren/generator.html)
Iver.
I don't have a dog in this fight - no intent to stay in a house where a winter storm might shut me down ever again - but it seems to me that there is a simple solution that would be code compliant for those of you that still do have reason to power your house from your bus. If you have a simple contractor's panel setup on a piece of plywood with enough four conductor cable appropriately sized to feed that sub-panel directly from your bus generator I believe that would meet the requirements of the code. When the storm shuts you down string out the cable, fire up the gennie and plug extension cords from that sub panel to whatever you need to keep running in the house. Somebody else can/will comment on the legality but it seems to me it would be legal and safe. More importantly it would likely spend 99.99% of it's life with the cable wrapped around the plywood, stored in the back corner of the garage so it wouldn't ever be a code issue anyway.
If it was me I'd just move into the bus until the storm blew over. And then I'd head south until the snow melted off the roof.
Quote from: artvonne on February 05, 2011, 10:40:16 PM
Are you saying to "remove" the bonding screw inside the house main panel, (unbonding the neutral from ground) when using an RV to generate power to your house?
That depends on how you are connecting the generator.
If the generator is to be connected using some type of permanently installed inlet with a transfer arrangement, then, no, you should not remove any bonding jumpers. Instead, the loads must be fed from a sub-panel with isolated neutrals downstream of the transfer gear, and the transfer gear must switch the neutral.
If you are connecting the generator to the panel with a temporary pig-tail wired directly in to the panel (no permanent provisions allowed with this arrangement), then you need to remove the incoming hots as well as the neutral and tape them off. The temporary pigtail connects to the same lugs that the permanent wires, now removed and taped, were using. In this sort of arrangement, if the "incoming neutral" actually originates as a jumper inside this panel, then, yes, you would remove and tape the jumper as well.
Quote
I have a 200a transfer switch that only switches the hots. If I used the RV to power the transfer switch, and the generator in the RV is bonded, how would you suggest grounding/bonding the transfer switch?
Sorry, but you simply can not use a transfer switch like this with an RV generator, ever. Not in your RV, and not to connect your RV to the house. Any transfer gear connecting to a bonded generator MUST SWITCH THE NEUTRAL. Period, no exceptions. Anything else is dangerous.
As I wrote earlier, generators made explicitly for fixed backup use are not bonded; they have floating neutrals. This type of generator is connected with a transfer switch that does not switch the neutral but rather passes it straight through.
HTH,
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
Bob
That was my suggestion at the beginning of the thread --- simple straight forward and yes code compliant as a TEMPORARY use panel.
Melbo
If I appear to be asking dumb questions, its only because I got electrocuted from a light switch once and have a very healthy respect for it. Too many people have the mistaken idea that 115 volt house current wont kill them. And they feel that way because without any load on the circuit you can let it pass through you and only feel a small shock. But if you become part of a circuit that energizes something, say a 60 watt light bulb as I did, you could truly get killed. In my case, I was instantly thrown across the hall and stunned. My fingers were burned and my arm hurt really bad and ached for over a year. I have no doubt that had there been more resistance on that circuit i probably wouldnt be writing this right now.
Having the RV power my house would be wonderful. Having someone walk up and grab the camper door and pass the entire load the house is drawing through thier body at 230 volts would likely be the last move they ever made. This stuff isnt a joke. And the fact so many professionals have differing opinions just makes it all the more confusing. When I rewired my last property, I ran power to out buildings using sub panels after bringing power in after the meter to the main panel. I understand all the grounds and bonding with that setup. But when it came to asking about the transfer switch even the electrical inspector got excited. He wouldnt tell me how to do it, said to talk to the generator company and have them do it. He went on to say people shouldnt have generators hooked up to their house, they were dangerous. When I asked the generator company, instead of simple answers, they said they couldnt offer any information without sending out a technician. Understandable, they want to make money.... No, I think they dont want to be sued, and there is quite enough risk here.
At any rate, this thread has opened my eyes even further to the dangers, and to the knowledge I need to study more. One thing that bothers me about running extension cords to circuits inside the house, backfeeding them. is that most are grounded back to earth. That could put live current onto every circuit that has the ground tied (bonded) to the neutral, theoretically bypassing every breaker in the panel. Its really something to think about.
QuoteSorry, but you simply can not use a transfer switch like this with an RV generator, ever. Not in your RV, and not to connect your RV to the house. Any transfer gear connecting to a bonded generator MUST SWITCH THE NEUTRAL. Period, no exceptions. Anything else is dangerous.
Sean, I changed my last post, the part with the transfer switch to a 3 pole switch. "I don't want to give anybody the wrong idea"
Now I have a question for you. If you are wired like I explained, then your breaker panel in your house is considered a sub panel correct? And in that sub panel all your grounds and neutrals are isolated. This means nothing in the house is bonded. If I connect a standard 2wire transfer switch before this panel, and my generator is still bonded.
How am I getting a double bond?
Gary
Im trying to go back to the beginning of this thread and re-read it. If I am understanding the problem correctly, the best setup would give the Bus its own transfer switch that carries all generated power away from the bus, and which isolates the generator from the Bus entirely?? I assume this would be the type of TS that also switches the neutral? That you could then carry three wire (two hots and neutral) to your home transfer switch and have your ground bonded there?
Quote from: artvonne on February 06, 2011, 10:32:40 AM
Im trying to go back to the beginning of this thread and re-read it. If I am understanding the problem correctly, the best setup would give the Bus its own transfer switch that carries all generated power away from the bus, and which isolates the generator from the Bus entirely?? I assume this would be the type of TS that also switches the neutral? That you could then carry three wire (two hots and neutral) to your home transfer switch and have your ground bonded there?
I think this is what we're getting at (all contained in the structure to be powered by the bus - not on the bus):
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi753.photobucket.com%2Falbums%2Fxx174%2FLonelyDodger%2FBuddyPower-1.png&hash=2b80e70e279028794f6fb1642c2bb19c1f6c7306)
-T
Quote from: Tim Strommen on February 08, 2011, 12:22:02 PM
I think this is what we're getting at (all contained in the structure to be powered by the bus - not on the bus)
Okay, but you left out whether the RV Generator has the ground and neutrals bonded or not.
In my case I intend to have a transfer switch that delivers generator power directly to the main panel, and will disconnect un-needed circuits to keep from overloading the generator. i notice in your drawing you are switching the neutal. I need to call the place I bought the TS as supposedly there is a kit to switch the neutral.
Quote from: artvonne on February 08, 2011, 12:35:21 PM...Okay, but you left out whether the RV Generator has the ground and neutrals bonded or not...
Sorry, should have used a bigger font... You would need to actually have that warning label on the input plug.
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi753.photobucket.com%2Falbums%2Fxx174%2FLonelyDodger%2FBuddyPower2.jpg&hash=4e9270391c3bd610ef83e28c1aa7da063a19f533)
In your case where you wish to power the entire main panel, the same general concept applies - you'd need to have the switch before the main pannel, and would need a main-breaker after the meter but before the main panel and transfer switch to protect the main entry conductors and transfer switch. The neutral would have to be bonded at that new main service entry breaker, and that main entry neutral separated by the transfer switch.
Like this:
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi753.photobucket.com%2Falbums%2Fxx174%2FLonelyDodger%2FBuddyPowerV2.png&hash=bdefd089806e54410ce361dfe0f9b1449b47a5e4)
-Tim
This discussion has got me re-examining my generator setup in the bus as well as how it connects to the house.
I have a 6500 Onan Generator that was a construction type generator (i.e. non RV type) It originally was connected for 120 V but I changed the wiring connections a few years ago to put out 220 so I could hook it up to the house and run out well water pump(its 220V) I then took off 120 from one leg for the bus. I realize this unbalances the generator but we don't use the generator very much and it has worked well for what we use it for. I can't see any labelling suggesting whether the neutral and ground are bonded or not. I have 2 hots and a neutral going to a "welder plug" that I use to run to the house. There is no ground wire and I'm not sure if the generator is grounded to the bus chassis. At the house I feed into the main panel through a breaker with a mechanical interlock which only allows EITHER the main breaker or the "bus" breaker to be on. In other words the main breaker can't be on at the same time as the "bus" breaker.
So first of all I'm wondering if the connection between the generator and the bus is safe and secondly what do I have to do to ensure the connection to the house is SAFE.
Thanks
Fred Mc.
Quote from: Fred Mc on February 08, 2011, 07:42:23 PM...I have a 6500 Onan Generator that was a construction type generator (i.e. non RV type)...
Generally - standalone "portable" generators (like yours) are internally bonded at the generator head (while it's powered off of course...). You can verify visually by pulling off the service panel at the head (there should be a jumper wire from ground (case) to some other pole.
Quote from: Fred Mc on February 08, 2011, 07:42:23 PM...There is no ground wire and I'm not sure if the generator is grounded to the bus chassis...
Use a multi-meter to verfiy that there is no connection to ground (chassis) on your bus. If it measures "open", you'll need to fix that first. If you get continuity, then you probably have a ground connection somewhere and you may want to hunt it down and relocate it to make it more obvious (ground should follow the hot/neutral lines - always).
Quote from: Fred Mc on February 08, 2011, 07:42:23 PM...So first of all I'm wondering if the connection between the generator and the bus is safe and secondly what do I have to do to ensure the connection to the house is SAFE...
You should have a ground to the house, that's for safety. Since the generator is vehicular mounted, it needs to retain its bond internally - this means that you must disconnect the neutral from the main power comany's service entry when you transfer your house loads as illustrated in the previously posted diagrams. You can verify that the bond is broken by not plugging in your generator and flipping the transfer switch to the Generator input. Then with a multimeter - check for continuity between the ground and neutral. If it's open - you're good. If there is still continuity, there is a double bond - and that's bad...
-Tim
I spoke to Katolight in Mankato MN, they are the generator company I bought the transfer switch from. I bought it several years ago for another house Iowned and never used it. I would have talked to them before I hooked it up, but this discussion really bugged me to want to know what I'm doing.
As has been discussed here, all portable and RV Gensets have neutral and grounds bonded, and that is NEC code for those type gensets. When you connect your house to a portable generator or RV however, it is no longer under the same code as a portable, you do not want the generator ground and neutral bonded in this situation.
While the man I spoke to said that many people connecting bonded RV generators to their homes get away with it, and that in most cases there isnt a problem, he also warned that just because you havent noticed anything, doesnt mean the problem isnt there. He said in one particular case, he measured 197 volts between a campers skin, and ground, when it was hooked up to a house and power was backfeeding into the ground.
His recommedation was to install a knife switch between the ground and neutral at the generator, so the switch becomes you bonding mechanism. On to bond, as when your running your rig, and off off to de-bond, when your powering your house. He said there really is no need to switch the neutral in a non critical system.
Fred Said"
"So in a standard 200 amp house main panel does the main disconnect (which is 240v) shut off the hots and neutral when it is shut off? How can you tell if it disconnects the hot and neutral?"
and Gary Said
"No it doesn't, it just shuts off the two hots. Even the main breaker at the meter loop only disconnects the two hots."
What confuses me is the fact that I can buy this product (http://www.interlockkit.com/ (http://www.interlockkit.com/)) which, as I see it, simply prevents the main breaker from being "on" while the generator breaker is "on" and does nothing to disconnect the neutral which, apparently is dangerous. What am I missing here as I gather from these discussions that unless both hots AND the neutral are disconnected from the utility you can still electrocute someone down the line. How do they get away with selling a product that can be "lethal".
Fred Mc.
Artvonne sed :
"As has been discussed here, all portable and RV Gensets have neutral and grounds bonded, and that is NEC code for those type gensets. When you connect your house to a portable generator or RV however, it is no longer under the same code as a portable, you do not want the generator ground and neutral bonded in this situation."
And I thought I'd point out that my newish Yamaha EF3000iSEB (what a dumb name) inverter generator has floating neutral. I have never been able to figure out why, but portable generators with floating neutral are indeed common.
Brian
Quote from: Fred Mc on February 08, 2011, 10:57:18 PM...What confuses me is the fact that I can buy this product (http://www.interlockkit.com (http://www.interlockkit.com)) which, as I see it, simply prevents the main breaker from being "on" while the generator breaker is "on" and does nothing to disconnect the neutral which, apparently is dangerous...
So there are two distinct configurations discussed here in this thread:
- Standby, permanent fixed-installation (hardwire, dedicated to the house - neutral not bonded)
- Portable, temporary installation (use a flexible power-cord to hook it up then put it away when you're done, take it with you to another jobsite, or vehicle mounted - neutral is bonded)
The "Interlockkit" device is designed to work in the first case since it just switches the hots, but you need a different setup if your generator is a temporary/portable type.
Quote from: artvonne on February 08, 2011, 09:10:05 PM...I spoke to Katolight in Mankato MN... ...His recommendation was to install a knife switch between the ground and neutral at the generator, so the switch becomes you bonding mechanism. On to bond, as when your running your rig, and off to de-bond, when your powering your house. He said there really is no need to switch the neutral in a non critical system...
They say that, but possibly without context/pretext of this thread (I have no idea). I actually take issue with their recommendation to install a knife switch at the generator, and here's why: You will now have to switch things at two locations (one at the transfer switch, one at the generator - possibly with tens of feet between the two devices). The point of an interlocked transfer switch is to ensure that the system is safe to operate before power is applied. Two switches that are not directly interlocked adds a significant risk, and operation complexity.
Will you always remember to flip both switches? What if you're in a hurry one time and forget to de-bond it? Also, what if you meant to re-bond it and while you were putting away the cord you got side tracked in a conversation and never remembered to re-bond it? What if you're not the one to hook it up or take it back down, will the operator know that they need to de-bond it or re-bond it? What happens if someone messes with the state of the bond/de-bond switch separately from the transfer? How can you prevent independant operation of the device when it's in-use?
It is solely for the advocation of safety that I recommend that if you are really planning on using your bus generator as a house back-up and you are conscious of this in advance (for instance planning to put in an input-plug in a box), why wouldn't you put everything in one device (i.e. the transfer switch)? This way the circuits are set up correctly by hard-wiring them appropriately for each power source, and any idiot can run the system safely (safe by design is better than safe by memory).
My opinion.
-Tim
I must apologize for being away from this thread, as I see some folks have asked me direct questions. I am away on a Red Cross training exercise and really have not had time to even read, let alone respond to, this board. I have a short break here but will again be tied up through the end of the week.
I note that in my absence, Tim has done a great job of elaborating on the issues.
I am very concerned about a recurring theme in this thread that I think needs to be addressed. Specifically, a number of folks have asked "Why would they sell Device X in hardware stores if connecting it to my house and generator is dangerous?" This is a lot like asking "Why do they sell matches if they can set my house on fire?" Neither matches nor non-neutral-switching transfer switches are dangerous by themselves, but they each can be used in dangerous ways.
As an example, both ungrounded, two-wire cable and grounded three-wire receptacles are available (and listed), but using them together is dangerous. Metal cable and plastic junction boxes are listed and are widely available but they can not be used together. Listing of a device, by UL, CSA, or any other lab, means the device is safe and approved to be used as designed -- it does NOT automatically make any installation of that device safe.
Household transfer switches (or interlocking breakers) are perfectly safe when used with a fixed-base, household backup generator, because such generators have floating neutrals. Likewise many portable generators intended for this purpose have floating neutrals and can be connected in this way. I would dare say that 99.999% of backup generator installations simply do not have the issue that we will have with our coaches, which is why the vast majority of transfer switches are designed without provision for switching the neutral.
On the flip side, RV's
always have this issue: if an RV is equipped for both shore power and a generator, any internal transfer switch must always switch the neutral. Manufacturers of transfer switches explicitly for RV use make their switches with neutral switching included.
What we have been discussing in this thread is doing something that almost no homeowner and even very few RVers would ever do: using an RV generator as a backup power source for a fixed house. BECAUSE IT IS NOT COMMONLY DONE -- ALMOST NO ONE EVER DOES IT -- YOU WILL NOT FIND INFORMATION, PARTS, DIAGRAMS, ADVICE, OR ANY OTHER MATERIALS ABOUT HOW TO DO IT CORRECTLY.
Now, I am sorry (just a little) for shouting, but this stuff is important. Doing this incorrectly can kill you, or someone else.
IF you propose to use your bus to power your house, you will be doing something that has probably not been discussed anywhere else on the Internet than right here in this forum more than a half dozen times. And you had better be sure you know how to do it right. I would bet real money that if you called a dozen professional, licensed electricians in your area, ten of them would get it wrong -- which is another reason it is so important for you to know what you are doing. There is no manual for it, and it is not explicitly covered in the code -- you need to know how to integrate the relevant parts of the code and apply them yourself.
The generator in your coach has neutral and ground bonded together. It is dangerous and unlawful to install a means, such as a switch, to unbond them. So in order to safely power your house from your coach, the neutrals in the house must be isolated and the transfer arrangement, whether that is a manual switch, automatic switch, interlocked breakers, or a temporary pigtail MUST SWITCH THE NEUTRAL.
Quote from: Melbo on February 06, 2011, 08:34:31 AM
...
That was my suggestion at the beginning of the thread --- simple straight forward and yes code compliant as a TEMPORARY use panel.
...
Only if it is lying around loose. Having it permanently attached or wired to anything is not TEMPORARY and is therefore not allowed, which is what I originally wrote in response. I read your original post as proposing a built-in sub-panel with built-in receptacles for this purpose, which is against code. I read Bob's suggestion as for a loose, rolled-up and stored system of panels and cables which would be deployed as needed. This is permitted, but I would point out that it is not different from the very first thing I wrote on this subject: power your loads with extension cords run back to the bus. Some folks felt that having extension cords (or temporary cables from a loose temporary panel) running all over the house was not what they wanted.
Quote from: Seayfam on February 06, 2011, 10:10:12 AM
Now I have a question for [Sean]. If you are wired like I explained, then your breaker panel in your house is considered a sub panel correct? And in that sub panel all your grounds and neutrals are isolated. This means nothing in the house is bonded.
Just because the bond is not in that panel does not mean it does not exist. The bond is somewhere upstream. There MUST be a bond at the service entrance.
Quote
If I connect a standard 2wire transfer switch before this panel, and my generator is still bonded.
How am I getting a double bond?
Because the neutral and ground from the bus generator are connected all the way back to the neutral/ground bond at the service entrance.
Quote from: Fred Mc on February 08, 2011, 10:57:18 PM
...
What confuses me is the fact that I can buy this product (http://www.interlockkit.com/ (http://www.interlockkit.com/)) which, as I see it, simply prevents the main breaker from being "on" while the generator breaker is "on" and does nothing to disconnect the neutral which, apparently is dangerous. What am I missing here as I gather from these discussions that unless both hots AND the neutral are disconnected from the utility you can still electrocute someone down the line.
I think we are confusing issues here. You will not electrocute someone working on the lines with the double bond. You are, instead, creating a dangerous situation in your own house/bus. Only a single line runs from the transformer to your house for the neutral (there is no separate ground) and any double-bond issue will not affect the power company. As long as the hots are disconnected by the transfer gear, such as the interlocked breakers you linked, the power company is happy. It is your own premise that is in danger from the double bond.
QuoteHow do they get away with selling a product that can be "lethal".
The product is not lethal by itself, it is the way it is used, or misused. Many products that can be lethal are sold every day, including handguns. The manufacturer is not responsible for how the product is used, only that it is safe when used as designed.
The product you linked is designed to be used with household backup generators, not RVs.
Hope that clears some things up.
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
I was trying to get around having two generators, but I think thats really the safest bet when everything is considered, not worth killing anyone through a stupid mistake. Does seem odd though, that a company that builds, sells and services generators from 15KW to 3000 KW wouldnt know code.
Whether or not it would meet code, I still think you would be safe under any circumstance by SECURELY bonding the generator frame, thus the bus frame to the house ground, using at least a #2 cable.
Quote from: Len Silva on February 10, 2011, 06:15:55 AM
Whether or not it would meet code, I still think you would be safe under any circumstance by SECURELY bonding the generator frame, thus the bus frame to the house ground, using at least a #2 cable.
I don't really belive that's a question we've been discussing here - grounding is grounding - everything that is metal (and not part of the neutral/hot power transmission) should be grounded and connected to the same ultimate ground point (i.e. a ground rid driven into earth) in a daisy-chain/star fashion and not include loops of ground. This includes the boxes, metal conduit, bus chassis - both in the house and on the bus...
Inconveniently NEC also calls the interconnection of metalic enclosures "bonding" and this unfortunate cross-terminology can create a heck of a lot of confusion for laypeople! Interconnecting the conduit, metal encolsures is "
bonding to ground" but there should only be one "ground to neutral
bond" in a system - ever! (have we gotten that point across yet? ;D)
Best,
-Tim
Just get another generator and hook it up to your house as a genuine standby genset. Obviously this is something thats not meant to be done, very few professionals have a handle on it, and a mistake could kill someone. That isnt a joke either. I know a lot of people play around with 120 volt and think its just a lil shock. That lil shock can become deadly if it has some wattage going through it. I know for a fact that 60 watts will throw a 220 pound man across a room and stun him (me). 8KW will light you up like the 4th of July and leave you smokin dead. Beleive it.
One of the inspirations for this thread is that many busnuts can barely justify the ca$h for the one used generator they have now. Some can only afford the one size fits all.
Powering the house during a power failure is not a luxury, depending on your climate or situation, it is a necessity. Further economic disaster, which cannot be afforded, will result if the house doesn't regain some power for critical systems like heat, pumps, refrigeration, etc, as the case may be.
The economic losses are more easily seen than the confusing electrical safety theory that is difficult to prove via simulation.
I started the thread to get the collective experience in one place, focused on the specifics of this challenging project, and hopefully, folks realize there are very few professionals out there that will be able to complete a safe install, and that those of us that might do this, need to go back and check what we think we know.
With these sorts of things, unfortunately, or fortunately, we never get to know that we saved a life.
happy coaching!
buswarrior
All I can say, is that if after almost 7 pages we dont have a CLEAR and SIMPLE answer.... If a company that has been in business for 53 years and builds generators from 15KW to 3000KW cant answer it properly.... If Elecrical inspectors dont want to touch it.... If Firefighters are warned to avoid it.... If power company linemen are scared to death of it....
Maybe we should be extremely careful how we approach it? Seriously, if highly trained electricians have a problem with it, and just plain say we shouldnt do it, then its something to really consider leaving alone.
The neutral is connected to the ground connection inside your main house panel to a ground rod buried in the ground. Ideally, current will always flow from hot to neutral, and any short will be directed to ground.
Your Bus generator has the neutral and ground connected together in the main panel too, but it is NOT grounded to earth, its grounded back to itself. Connecting your Bus generator to the main panel in your house, the Bus is now putting hot current potential into the earth, something that wouldnt happen "inside" the Bus. Now, when you step up to the Bus, or come out and step down to the ground, you could potentially offer a better neutral current path THROUGH THE EARTH, back to the main panel, than the neutral running back to your main panel. It is very important everyone understands this point.
The only safe way to do it, is to have the neutral and ground seperated in the Bus when generating power to your home and have the generator completely isolated, retaining the bond in the house main panel. But you have to have the neutral and ground bonded again when generating power "inside" the Bus. As others have said, one mistake, one time when you forget to make the switch one way, or the other, could kill. Its fine if it kills me. Not so fine if it kills my kid, or my grandchild, or anyone else. A knife switch would certainly work to BOND and DE-BOND the generator connection, but one mistake, one way or the other, could be deadly. The bond connection needs to be physical and permanent.
I know many are trying to get by on a shoestring, and I know many of us dont always feel we need a lot of oversight over so many things. But a life is pretty valuable these days, a lot more than a dumb generator. Another thing to consider is what would happen if you were absent and someone else had to unhook your rig, you wife, your son, a friend. Would they reconnect things back the correct way? Ive read enough here to decide its just plain not worth messing with.
Quote from: artvonne on February 11, 2011, 08:20:36 AM
All I can say, is that if after almost 7 pages we dont have a CLEAR and SIMPLE answer...
Art, I have provided a crystal clear answer that is as simple as possible. I have written it three different times three different ways because some people want to continue to argue that there must be something easier -- there is not. I will now write it a fourth time, in numbered order:
1. Isolate the neutrals in your house distribution panel, if they are not already. Kits are sold in hardware stores for every make and model of panel to do just this; the kit is about $15-$20. The task is tedious and time consuming but not difficult. Do it now -- it will be too late when the power outage happens.
2. Install transfer gear upstream of this panel which transfers all hots and neutrals; usually that means three wires or "poles." This can be a manual switch, an automatic switch, a pair of interlocking circuit breakers, or a junction box with lugs where the wires can be removed to connect to a generator pigtail. It can even be the original input lugs in the house panel, so long as there is a main lug for the neutral where it can be safely removed.
3. Relocate the house's ground-neutral bond upstream of the transfer gear if it is not there already.
4. Connect the bus generator to the transfer arrangement you installed in step 2.
Done. Safe, simple, effective, inexpensive. You ought to be able to do all of this with less than $30 in parts from Home Depot for the pigtail solution; a transfer switch or breakers is more and will depend on the size of your house service.
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
"Isolate the neutrals in your house distribution panel, if they are not already. Kits are sold in hardware stores for every make and model of panel to do just this; the kit is about $15-$20. The task is tedious and time consuming but not difficult. Do it now -- it will be too late when the power outage happens."
Sean, can you point us to a website that might have a picture of such a device. It helps when you go to the borg if you kinda have an idea of what you are looking for as they don't always understand what you are talking about.
Thanks
So just to re-iterate so I have this clear in my mind.
1. I get a kit that allows me to isolate the neutrals in my house panel.
2. I install a transfer switch that switches both hots (but not neutral) from utility to generator i.e. the generator and utility can't both be on at the same time.
3.I hook up my generator that is neutral bonded.
4. The bonding occurs in the generator and not the house panel.
Thanks
Fred Mc.
Quote from: Fred Mc on February 11, 2011, 10:17:02 AM
...
Sean, can you point us to a website that might have a picture of such a device. It helps when you go to the borg if you kinda have an idea of what you are looking for as they don't always understand what you are talking about.
Here is a photo of an isolated neutral panel:
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwww.hammerzone.com%2Farchives%2Felect%2Fpanel%2Fsub_panel%2F01%2Felspra45ax.jpg&hash=a2691eb06c3d801093d1e759b3991a347f4cd178)
In the photo, "3" is the ground buss, bonded to the panel. "2" is the isolated neutral buss, which has a cross-tie to a neutral buss on the other side of the panel for convenience. "1" is the incoming hot power.
Here is another, smaller panel with an isolated neutral on the lower left, and ground on the right:
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fimg340.imageshack.us%2Fimg340%2F3919%2Fimg0037h.jpg&hash=5276a822fd730d7c5f944b05ee0be4c94f6fe0cd)
A kit for a small load center can be found here:
http://allmmj.com/index.php?option=com_community&view=photos&task=showimage&tmpl=component&imgid=1265&maxW=996&maxH=597 (http://allmmj.com/index.php?option=com_community&view=photos&task=showimage&tmpl=component&imgid=1265&maxW=996&maxH=597)
This one has space for eight branch neutrals and the incoming main, so it would be for an 8-space panel.
The isolated neutral buss is usually specific to the make and model of your panel. You might have to special-order it or go to a supply house, but HD and Lowe's typically carry the ones for the panels that they sell in-stock.
Quote from: Fred Mc on February 11, 2011, 10:23:11 AM
...
2. I install a transfer switch that switches both hots (but not neutral) from utility to generator i.e. the generator and utility can't both be on at the same time.
No, it must switch both hots AND the neutral. Three poles or contacts in total.
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
Sean
Ive read what youve written. I am not really arguing it so much as simply giving up on the whole idea. First, In my case I already have $800 into a Transfer switch that does not switch neutrals, there is no kit available to change it, and ill never get my money back out of it. Second, in your own words, 10 out of 12 licensed electricians dont know what they are doing with this kind of hookup. In fact, I doubt many electrical inspectors would approve it no matter how it was done. I know the last one I dealt with got very nervous when I mentioned a standby generator. Third, the place that sold the Transfer switch and builds generators wasnt that familiar with this kind of hookup. And fourth, telling anyone here how to do it could create a very dangerous situation if they do it wrong and they believe you told them how to do it it. It could come back to haunt you. Just saying no, or I dont know, seems the better choice here IMHO.
That said, I do question the safety of keeping the Bus/RV generator neutrals bonded to the Bus chassis when connected to a home electrical system. If the gen is grounded to the Bus chassis along with the neutral, and the home electrical neutral is bonded to the ground rod in the earth at the main panel, under the right conditions it would seem your body could become a conduit if there is any potential between the Bus neutral and the ground rod. Maybe im just not seeing it right, but im totally uncomfortable with it now. I was thrown hard across a room into a wall once, and landed on the floor completely stunned and with my arm hurting like hell and my fingers burned after getting bit with 120 volts, and my arm hurt for over a year. I have a lot more respect for it now, lol.
Anyway, I just dont like the whole idea anymore. Generators arent that expensive, and having a real dedicated system for the house with permanent mechanical connections is a better deal anyway.
Quote from: artvonne on February 11, 2011, 11:17:35 AM
... telling anyone here how to do it could create a very dangerous situation if they do it wrong and they believe you told them how to do it it. It could come back to haunt you.
This is the reason that you will never see me suggest anything here that is not safe AND code-compliant.
Quote
That said, I do question the safety of keeping the Bus/RV generator neutrals bonded to the Bus chassis when connected to a home electrical system. If the gen is grounded to the Bus chassis along with the neutral, and the home electrical neutral is bonded to the ground rod in the earth at the main panel, under the right conditions it would seem your body could become a conduit if there is any potential between the Bus neutral and the ground rod.
That is exactly correct. However, unbonding the generator in the coach has its own dangers (and is against code), which is why I keep coming back to making the proper changes at the house end instead.
I respect your decision to get a proper backup generator so you can protect your $800 investment in transfer gear. It is ultimately a safer solution anyway. However, many people are following this thread and if they are insistent on using the bus for backup power, they need to see the right way to do it.
-Sean
http://OurOdyssey.BlogSpot.com (http://ourodyssey.blogspot.com)
Clarity:
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi753.photobucket.com%2Falbums%2Fxx174%2FLonelyDodger%2Fportable_power.png&hash=c590da37f64992734251b8164ee129dd2d30f791)
Quote from: Sean on February 11, 2011, 11:34:43 AM...I respect your decision to get a proper backup generator so you can protect your $800 investment in transfer gear. It is ultimately a safer solution anyway...
I second this...
Quote from: artvonne on February 11, 2011, 11:17:35 AM...That said, I do question the safety of keeping the Bus/RV generator neutrals bonded to the Bus chassis when connected to a home electrical system. If the gen is grounded to the Bus chassis along with the neutral, and the home electrical neutral is bonded to the ground rod in the earth at the main panel, under the right conditions it would seem your body could become a conduit if there is any potential between the Bus neutral and the ground rod...
This is a HUGE reason, that in NEC any exterior mounted/serving outlets
SHALL be protected by a Class-A (<6mA) GFCI device between the bond and the outlet!!! If there turned out to be any potential across the neutral and ground that exceeds 6mA (often they trip as low as 4mA), it would pop the GFCI device and you'd be safe. What goes out on HOT and doesn't come back on Neutral can be assumed to be returning on Ground due to the bond at the power source (but only with one bond in the system). I think you're obviously on to the idea for how potentially dangerous this can be.and have the correct caution while approaching it...
Quote from: Sean on February 11, 2011, 11:34:43 AM...unbonding the generator in the coach has its own dangers (and is against code), which is why I keep coming back to making the proper changes at the house end instead...
I also second this - I would also offer for clarity of those reading this thread, that unless you have properly set up a load (house) to be plugged in to a portable generator - as a general rule, you should not plug your bus generator into the load. This comment is intended to emphasise that nothing we've stated on this thread suggests that anything removes responsibility from the operator to check that the load they are attaching to is correctly set up for the power source you give it. Like Sean's earlier comment, a device is safe by "listed" design practices and testing - it is always up to the installer/user to use these things correctly (so don't just plug into a neighbor's generator power input plug without ensuring it is correctly set up...).
{bad_humor}"Guns Don't Kill People, People Kill People With Guns" = "Electricity Doesn't Kill People, Electricians Kill People With Electricity"{/bad_humor}
-Tim