Bonding article thread

[Chaz]

Hey Guys,
  I think I read a thread, in the not too distant past, with an article someone posted about bonding and all that goes with it. I remember it was rather extensive. (maybe came out of the Magazine) I'm too that point and am trying to find it.
  I have a 7.5 kw that I'm shoehorning (with a plasma cutter  )into my bus but I need to know what I'm doing when it comes to the wiring. Jerry L. has been helping me out with stuff like this but I was wanting to get myself a little "education" also. And having a reference around is also a good thing.
I understand a person can wire in some sort of normally open relay; cut the ground on the generator; or just plug into the generator or post with the same cord so as to never have the two connected at the same time. I'm really hoping for some good guidance on this so I don't let the "smoke out of the box". BTW I have a Xantrex 24v inverter.
  Thanx again!
     Chaz

[bevans6]

This thread?  http://www.busconversions.com/bbs/index.php?topic=16322.0

I think the complexity with Sean's inverter is it's built in transfer switch and how it treats neutral.  Other inverters with built in transfer switches, and other stand-alone transfer switches may not have that issue.

The simple idea, as I understand it anyway, is that ground needs to be bonded to neutral at the source of the power.  You will end up with three sources of power - the cord (pedestal outlet), the inverter, and the generator.  Each must bond neutral to ground as a supply source, but only when they are the selected source of power, because there can only be one bonding point at any given time.  You accomplish this with automatic transfer switches, and you will need two of them.

What I would do is this (I just spent the afternoon sketching out my planned inverter install).  I use 30 amp 120 volt power, so I use Iota single phase transfer switches http://www.thesolar.biz/IOTA_Transfer_Switches.htm that switch both power and neutral with relays.  They have a priority input, a secondary input, and the output to the load.  I have decided that my first choice for power is the cord to the pedestal, the second choice is the generator, and the third choice is the inverter.  I have the cord tied to the priority input of the first switch, and the generator tied to the secondary input.  The output of that switch goes to the priority input of the second switch, and it's secondary input is fed from the inverter.  If the cord has power, it is fed through both switches to the distribution panel.  If the generator has power and the cord does not, the gennie is fed through.  Only if there is no power from either the cord or the generator does the inverter supply power.  Neutral is switched all the way through along with power, and each source bonds neutral to ground when it is selected.  Everything shares the same chassis ground.

There may be a three way transfer switch that does all this, but I don't know of it, and I already have one of the Iota's so I just need to get one more.  If your inverter has a built in transfer switch and generator start and all of that, it will be wired a little differently per their instructions, but this is the basic idea. 

Hope this helps a bit.

Brian

[Timkar]

Quite a good article on the "other" board from FMCA..

http://www.busnut.com/bbs/messages/11/36147.html?1274197923

[Chaz]

OK............. 
I'm getting my "asked for education" but I'm afraid my final grade isn't going to be too good. 
I'm reading the articles and "kinda" getting it but am still a little concerned. I even printed them out to have as referencematerial.
I have a 4024 Zantrex. (It seems I may have to disconnect a filter capacitor as well, as per Sean in the other thread.)
I guess with all the remedial study I'm going to have to do I'm wondering if I can just get away with plugging my shore cord into my generator or into the pole and not have to worry about all this. My problem for right now is just time. I want to take a small trip Friday - Sunday and I don't think I can get the parts I need in time, much less get all the work done I need to do, to go. Plus, I'm not overly worried about having to unplug from the Gen and then plug into the pole altho the 4024 is supposed to be full of options that can make life easier in that regard. (I just woundn't know how to act if life were easy!  )
  Thanx fellas,
   Chaz

[Melbo]

IF and please note that is in CAPS IF you have an outlet on your gen and a cord that is wired properly for an outlet at a campground you can get away with moving the plug from outlet to outlet --- throwing in the inverter in the mix makes things a little more interesting --- the inverter gets power from the batteries and supplies it to your 110 or 120 panel --- we are back to the IF --- IF your inverter does the pass thru thing then you would send 30 amps to the inverter and it would send it back out --- the 30 amps can come from the gen or land line--- Now you need a sub panel with a max supply and output of 30 amps (yes yes yes or there about could be 40 or more or less) -- if there is no electric supply to the inverter it sends the power out from the batteries.  NOW how about a little twist in the interesting part of this --- if your inverter has power sharing AND you over tax the land line or genset the inverter will pick up the difference from the battery bank -- when your demand settles down "typically" (please note that was in quotes) the inverter will "refill your battery bank" so I am not sure if I confused or helped you --- Just remember "everything you know is wrong" a quick quip from firesiegn theater --- I'm sure someone will chime in with "REAL" and "ACCURATE" information.

Melbo

[bevans6]

I would say you could just plug into whatever source you wanted, as long as you make sure the generator is grounded to the bus chassis, and that it ties neutral to ground.  All the switches do is make it automatic.  The deal with the 4024 in the other thread was that it pops GFCI breakers because of it's design.

Brian

[rampeyboy]

I don't know much about this stuff, but I'll offer this, my Travco S&S uses a manual disconnect. When hooking to shore power, I plug the shore cord in normally. When using the generator, I plug the shore power cord into the generator "outlet". This way it cannot be hooked to both simultaneously. Now how this all relates to the nuetral, I don't know, but it must work. It's simple and effective I think.

Boyce

[Chaz]

Thanx guys.
I'm with ya Boyce. I'm thinking I can get away with this idea for now. I would like to use the full features that the 4024 offers eventually (that's why I bought it) , but for now, if just plugging into one or the other works, it will do. I guess I will need to buy some switches/relays as it were, to do it correctly.

It won't be a problem grounding the gen. obviously, but I was kinda curious about that too. I understand that a ground wire can be cut in the gen. to correct one of the issues. Which one or why.......I dunno.

I don't have an outlet wired on the gen yet, but that "should" be easy enough.
I'm not sure what all the 4024 can do but I'm hoping it will work ok. Sean would probably know - if he could chime in here.   I do know that the inverter is supposed to be able to take and give "juice" wherever and whenever needed.

As far as the gen. goes, it has two hot legs coming out and a neutral. I guess I will take the ground physically off the side of the unit.

If anyone has any suggestions, I'm all ears! 
Thanx again,
    Chaz

[Dreamscape]

Chaz, I've used the KISS method on ours. Seperate breakers for pole and genset. I do have an automatic device but have not installed it yet. I'll install it when I have an inverter and a batt bank. For now our process works just fine. I like the idea of me picking where I get my power from.

When you have time to sort things out and understand how it's wired, go for it. Sounds like you don't have the time to do it properly, and you want to keep the smoke in.

HTH

Paul

[bevans6]

separate breakers means it's also very easy to connect the gen to the mains supply, and probably blow up the gen.  Of the ideas so far, that's the one I would not do, unless there is some interlock that I haven't considered.

Brian

[Sean]

Sorry, guys, but if you have a Xantrex/Trace SW series inverter, it is NOT as simple as putting a plug on a cord and moving it from generator to shore or vice-versa.

Either way, you still MUST add the ground-neutral bonding/unbonding relay as shown in the SW-series installation manual.  To do otherwise will create an unsafe and possibly deadly situation.

Now, if you do use a manual cord-and-plug system for selecting between shore and generator (and this is, indeed, the simplest possible solution), the the bonding relay is fairly simple and can be implemented exactly as shown in the manual.  Note that this relay (if not the SW inverter itself) will cause GFCI campground receptacles to trip; I addressed this in the other thread.

If you instead use an Automatic Transfer Switch (ATS), then the ground/neutral bonding issue becomes more complex, depending on the ATS design.  A detailed discussion of all the possible ways this could be done with all the various ATS systems out there would take several pages.

Remember that ground and neutral must be bonded to each other in exactly one location.  No bond at all is extremely dangerous, and more than one bond is moderately dangerous.  Either can kill you under the right combination of circumstances.

Properly installing an SW series inverter in an RV is non-trivial, and I would guess that most RV service shops and even many licensed electricians would not know how to do it correctly.

If you are under the gun to make a trip in your rig but do not have the time to install the inverter correctly, I would suggest you leave it disconnected entirely and do not use it.

And just to be clear, I am talking here about the SW series, such as the SW4024 and the SW2512; other models of inverters generally do not have this problem and are much simpler to install.

FWIW.

-Sean
http://OurOdyssey.BlogSpot.com

[Dreamscape]

separate breakers means it's also very easy to connect the gen to the mains supply, and probably blow up the gen.  Of the ideas so far, that's the one I would not do, unless there is some interlock that I haven't considered.

Brian

Brian, That is the way the PO had it and I've only used the genset a couple of times off grid. I just remember to shut one off before I turn the other breaker on. I know it's not right and it'll get fixed when I have the time. It will be either/or when I'm finished.

[bevans6]

Dreamscape, I hear you on the PO.  I had to pull out 100% of his wiring, and 50% of his plumbing, and I'm not done yet!  My next task is to vent the black/grey tank properly so the odour stays outside, not in the bedroom!

Brian

[Chaz]

Thanx all!
  Brian,
   But to be clear, the way I read what Paul said was that he physically plugs his cord into where he wants to get his power from. So it's my assumption that until he puts in an "automatic device", he is OK. (??) At least I'm hoping so for Paul. If not, time to do some changin.   
  Sean,
  I installed a relay, whatever, in my breaker box that takes care of my problem.....at least it did with my last generator. Jerry helped me out with that one. But it looks as tho I will need to understand and implement what you wrote in your other article in case I run into a GFIC.
  Thanx again for all the help!!! 
  OH!!! And did you guys know 50 amp cord was soooooooooooooooooooo expensive!!!!! MAN!!!!!!!
    Chaz

[bevans6]

The thing about Paul's installation is that the opportunity to make a mistake exists.  At the end of the day, the opportunity to make a mistake is all around us, in everything we do.  As you and he point out, all that's needed is a little care, unplug one before you plug into the other, it's been that way for a long time and nothing bad has happened yet.  In my old age, I forget things, I do things in the wrong order, I plug something in when I shouldn't from time to time, so if I can stupid-proof something I like that a lot!  Plus I think about what if my wife has to do it some time, I'm not around, and while a very intelligent woman she is not experienced with electricity the way I am.  So why not build in a fool-proof system?

Brian