I am thinking of reworking some of my wiring by removing the breaker box and replacing it with two smaller ones. One would be just those circuits serviced by the inverter. One problem I have is space for the panels. I was thinking of saving space by using a smaller panel and double tapping some breakers. My thought was that I could put one AC and one electric heater on the same breaker. Although the total load would be greater than the 20 amp breaker rating, I do not see any situation where I would be using both heat and AC at the same time. Does that make sense?
If you lose the wiring (short) on one circuit, you lose both circuits. What brand breakers are you using?
Depending on what type of breakers you're using, perhaps you can get tandems - two breakers that fit into one slot. I know that Square D makes them for the QO load centers.
The idea of running both the AC and electric heat on the same breaker might sound good now, but down the road it could lead to unintended results. My vote is to keep things up to code as much as is possible. I'd avoid the double tapping.
Alternatively, could you add a sub-panel that you could use to mount the additional breakers you really need?
Or, have you explored using a marine panel? There are some very compact panels for 120v systems that are used in marine applications that might suit your needs and allow you to install the correct number of breakers. There are also some marine panels that are actually two smaller panels combined into one housing, with the end result being like you describe with the inverter powering one half and the shore/gen power on the other half.
I see no problems running the A/C and heat off one breaker as long as you don't turn them both on at the same time. Worst case, you pop a breaker. I was an electrician in a previous life and personally I like a lot of breakers as others have noted. I would try to make room for a bigger panel at all costs and run as many circuits as possible because once you get things closed in, it is 10x harder to run more wires.
Two panels is fine too. I have two 120V panels in my bus. One for the inverter circuits and one for Shore/Generator circuits i.e. A/C, heat, Microwave. As for double-breakers, I have used those but only when necessary. Wiring gets a bit tighter when you try doubling breakers, but that would be a viable solution to run the A/C off one and heat off the other side. You also need to keep in mind when you are hooked up to 50A, you are running two separate legs and they should be balanced throughout your panel but that is an entirely different subject.
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Gary
The simple act of double tapping is not much of a concern since one can get breakers that are design for it or just use a wire nut to combine two wires to one that would go to the breaker. The original owners ran his wiring for convenience so that lights on one side of the coach are on a separate circuit than lights on the other side. In other words, there might be just four LED bulbs on one circuit. So combining those circuits seems to be of no consequence. It is in combining a heat circuit with an AC circuit, knowing that the breaker could not really service both, that I am toying with. But I just don't see why I would consciously turn on both heat and AC at the same time (if I did, I probably should not be driving a bus anymore).
Richard: I do not know anything about marine panels, so I should research that.
Gary: Actually, I only have one leg of 50 amps that serves both bars in the panel. I do not have any 220v loads, so this has worked fine allowing me to have a three wire shore cord that is 25% lighter. I probably should try to figure out a way to squeeze bigger panels in. My current single panel is about 10x12. For two 4space/8circuit panels it looks like I need a good 14x14, so something else might have to be moved. I do intend to use double breakers also.
How did you end up with one leg of 50 amps? That's a rather unique situation.
Here's just one example of a marine panel so you can see some of the options. They are not the cheapest, but they do pack a lot into a small space.
https://www.go2marine.com/product/162182F/ac-12-position-breaker-panel-5301-paneltronics.html (https://www.go2marine.com/product/162182F/ac-12-position-breaker-panel-5301-paneltronics.html)
Lots of other options out there. We've got a similar panel on our Custom Coach conversion, and the fact that it takes up so little space as compared to a household style box is why we haven't changed to something else yet.
Here in New Mexico evaporative cooling is very common and one breaker serves both the furnace and the cooler. The difference that I would see is that here when the cooler is in service the furnace is unplugged or if the furnace is in service the cooler is unplugged. They share the same duct system so only one appliance is used at a time. Kind of like some people do not use transfer switches they physically move a plug to switch between generator and shore power.
Good luck with your planning. A schematic is probably the best place to start and work from there.
GE used to make a very compact panel. I have installed them on older homes where there was not much room for a new panel. Something like an 8 inch by 12 inch with like 8 circuits.
GE Energy Industrial Solutions TL412CP Main Lug Indoor Load Center, 125-Amp
HTH
Melbo
Once I overcame the "Green Acres effect" by actually testing loads to determine the best way to wire things, I've been quite happy with the results of over loading my breakers. But then my 120v system is only 30 amps with 2, 15 amp slow blow breakers. Jack
FWIW,You could be safe as well as in line with the code ,from your breaker feed a double throw switch then feed your ac and heat off the switch .This way it is impossible to have them both on at the same time.
my coach is exactly that way and has been for ever. (I've owned it since 02-03) but, i have tandem breakers on 110v (ok 120v :) ).
my heat AC <are 220v> and hot water <110v> are not on the inverter.
everything else is. obviously, the inverter/charger is on the main too.
and i have a piece of 6/4 that i can jumper the sub if i had to have work done on the inverter...i tape back the red wire...or was it the black ? :)
but, now i carry a spare inverter too.
because I might be a hoarder :)
the inverter fed sub-panel has been in service 24/7 for 16 years, except for short periods of down time...
inverters need tlc too.
I have three circuit breaker boxes. One for shore (one leg of 50amp) or generator (two legs of 50amp wired straight 120vac). Then main circuit breaker box with one 30amp circuit feeding through inverter to my inverter circuit breaker box. All Murray from Home Depot. Simple, easy to service, but everything is manually operated. Good Luck, TomC
I like the idea of the three way switch. Be sure that it is rated for the amperage that you would run through it. It would keep you from having both appliances on at the same time and would save you a breaker space in the panel. You would know when you are going to need heat or cool and just flip the switch from one setting to the other.
Melbo
Richard: When I did the electrical on my last bus, I chose to make it with just one 50 amp leg. I put a jumper wire in the panel to reach the other bar. I worked fine since I do not have 240v loads. I thought at the time that it was probably unique. However, when I bought this bus it had a similar setup. This makes it either a very large coincidence or that there are a lot more out there who used similar logic. As mentioned, the shore cord is 25% light and therefore easier to handle and store. The marine panel looks interesting but I would probably go with a more budget solution.
Eagle: Thanks for the reminder to have some bypass system in case the inverter fails. On my present system I manually move the plug from shore to generator. The transfer switch switches from shore/generator to inverter. Even that has a bypass system though. Since the transfer switch probably should be replaced, I thought that this might be the time to change the system a bit. Although it generally works fine, there have been times when I forgot to turn off the water heater when the system switched automatically to inverter. In that case, it does not destroy the batteries but does let them run down to around 10v for the inverter to close down.
Now, I wanted to throw out a hypothetical idea. Suppose instead of using two small boxes, I just use the box I have now changing it around a little. What if I put all the non-inverter loads on one bar with one more circuit for the inverter? The inverter could than feed the other bar where all the low amperage circuits would be. Is there something inherently evil about that? In my case there could be a problem due to the generator, which actually does supply 2 50 amp legs to the panel. Of course that could be modified but I am not sure that is alright to do.
Quote from: Lin on June 11, 2018, 02:00:29 PM
Richard: When I did the electrical on my last bus, I chose to make it with just one 50 amp leg. I put a jumper wire in the panel to reach the other bar. I worked fine since I do not have 240v loads. I thought at the time that it was probably unique. However, when I bought this bus it had a similar setup. This makes it either a very large coincidence or that there are a lot more out there who used similar logic. As mentioned, the shore cord is 25% light and therefore easier to handle and store. The marine panel looks interesting but I would probably...
I think I understand, but how do you plug in when you're not at home? Or do you?
Our current bus, as well as our old bus, were both built by Custom Coach. They also used a non-standard method by running two 30-amp hot leads instead of two 50-amp. Not sure why, but it took a while to figure out on our first one since someone had installed the wrong receptacle for the shore cord.
Whatever you do, my suggestion would be to be sure to label everything and make sure that someone can't accidentally plug it into the wrong type/style of power source.
It works with a standard 50 amp rv receptacle. The plug is wired to only three blades (hot, neutral, ground). I actually have removed the fourth blade from the plug since it serves no purpose. I only have a 30 amp connection at home, so we use a common adapter pigtail.
Quote from: Lin on June 11, 2018, 02:00:29 PM
Richard: When I did the electrical on my last bus, I chose to make it with just one 50 amp leg. I put a jumper wire in the panel to reach the other bar. I worked fine since I do not have 240v loads. I thought at the time that it was probably unique. However, when I bought this bus it had a similar setup. This makes it either a very large coincidence or that there are a lot more out there who used similar logic. As mentioned, the shore cord is 25% light and therefore easier to handle and store. The marine panel looks interesting but I would probably go with a more budget solution.
Eagle: Thanks for the reminder to have some bypass system in case the inverter fails. On my present system I manually move the plug from shore to generator. The transfer switch switches from shore/generator to inverter. Even that has a bypass system though. Since the transfer switch probably should be replaced, I thought that this might be the time to change the system a bit. Although it generally works fine, there have been times when I forgot to turn off the water heater when the system switched automatically to inverter. In that case, it does not destroy the batteries but does let them run down to around 10v for the inverter to close down.
Now, I wanted to throw out a hypothetical idea. Suppose instead of using two small boxes, I just use the box I have now changing it around a little. What if I put all the non-inverter loads on one bar with one more circuit for the inverter? The inverter could than feed the other bar where all the low amperage circuits would be. Is there something inherently evil about that? In my case there could be a problem due to the generator, which actually does supply 2 50 amp legs to the panel. Of course that could be modified but I am not sure that is alright to do.
I understand what you're doing.
obviously the inverter charger needs to be on the shore leg.
on mine, i just tell the inverter i'm on a 30 amp source..
i think it keeps my pole bill lower..when rv parks meter.
my refridgerator has been on the inverter since 2002.
and yes, I full time.
on the road or in NP's gen time every 36-48 hours snaps the batteries full in no time (130 amp charger)
But, you create a nightmare for the next owner :)
It need not be a nightmare for the next owner if it is documented.
Is there anything wrong with using only one leg off the generator?
Quote from: Lin on June 11, 2018, 02:21:21 PM
It works with a standard 50 amp rv receptacle. The plug is wired to only three blades (hot, neutral, ground). I actually have removed the fourth blade from the plug since it serves no purpose. I only have a 30 amp connection at home, so we use a common adapter pigtail.
Very interesting. Many people that do this kind of stuff don't understand power correction costs, most if not all commercial electric accounts get charged fees for power factor and unbalanced power usage. Residential does not get charged for power correction.
So if you and several others are all pulling off a single leg, I would think the fees for the campground could be pretty large.
There are special transformers that will take 240 split phase and transform it into a single leg, and vise versa. I think they are called autoformers.
SD
Quote from: Lin on June 12, 2018, 06:52:11 PM
Is there anything wrong with using only one leg off the generator?
Yes, an unbalanced load will burn the windings eventually. As I mentioned above this is what an autoformer is for, it will automatically balance the two sides of split phase.
SD
Quote from: Lin on June 12, 2018, 06:52:11 PM
It need not be a nightmare for the next owner if it is documented.
Is there anything wrong with using only one leg off the generator?
Many bus owners have a hard time grasping conventional electrics. :)
Solardude: Suppose several campers were doing as we do and draw off only one leg, would the extra commercial charges also occur if they were roughly divided between the two legs or only if they all were pulling off the same leg? It would seem probable that people choosing which leg to use would be random and thus be divided. The autoformer looks interesting.
Another question then-- Our generator is really supplying two 50 amp legs, so we have real 240v at the panel even though we do not use it. When traveling down the road we generally run only the front AC, so the load is completely on one leg. Is that therefore also weakening the generator?
Eagle: I do not know whether I will actually try this, but it does seem intriguing because it would be so easy to do; just little more than rearranging the breakers (I love easy these days). With that in mind, I suppose I could simply replace the transfer switch and be done with it and just keep remembering to turn off large loads when switching to the inverter.
There should be a way to wire your generator to the load center so that the entire capacity is available and not just one leg. When I talked to the tech at Wrico he was recommending this if I did not have any 240v loads.
Thanks Richard, that makes sense. I will try to research that although this is a 40 year old Kohler.
Quote from: Lin on June 13, 2018, 10:40:16 AM
Solardude: Suppose several campers were doing as we do and draw off only one leg, would the extra commercial charges also occur if they were roughly divided between the two legs or only if they all were pulling off the same leg? It would seem probable that people choosing which leg to use would be random and thus be divided. The autoformer looks interesting.
Another question then-- Our generator is really supplying two 50 amp legs, so we have real 240v at the panel even though we do not use it. When traveling down the road we generally run only the front AC, so the load is completely on one leg. Is that therefore also weakening the generator?
Eagle: I do not know whether I will actually try this, but it does seem intriguing because it would be so easy to do; just little more than rearranging the breakers (I love easy these days). With that in mind, I suppose I could simply replace the transfer switch and be done with it and just keep remembering to turn off large loads when switching to the inverter.
My inverter fed sub is jumper-ed to feed both legs being 120v on both sides.
works fine. 3kw Xantrex Freedom Marine.
My main is 240v (one leg to each side per standard code wiring) as my heat and AC are 240v. I am an all electric coach.
I am at a loss to understand why (if) a gen puts out 240v then why wouldn't one
(a.) wire the coach to use it
(b.) wire the coach to use it
(c.) :)
Quote from: Lin on June 13, 2018, 10:46:55 AM
Thanks Richard, that makes sense. I will try to research that although this is a 40 year old Kohler.
We must have the same generator then...
Eagle: That is necessary for an all electric coach, but for one the uses propane it can be considered optional. We have two AC's (35 foot bus). We rarely use more than one at a time. The water heater is ten gallon 120v. Once the water is heated, it will generally stay warm most of the day if turned off. Even if left on, it only draws current intermittently. There is not need for 240 except if we really just wanted 100 amp instead of 50 amp capacity. I find that 30 amp requires power management, but 50 amp covers us fine.
The coach was wired to function off one leg. However, the PO installed a 7kw generator that is supplying on two legs. I think that he must have just got a deal on the generator and installed it as is to his already installed 120v system. As a result, the panel is sharing one leg to both bars when plugged into shore, but the two bars are fed separately when the plug is moved from the shore receptacle to the generator receptacle (the jump wire is in the shore receptacle). However, if I wanted to try to transform the system to use one bar for large loads and the other bar for inverter loads, then the generator would apparently be best modified to produce only 120v. One of the interests in this hobby is the ability to solve a problem in an unconventional way on a small scale just for the fun of it.
Richard: Did you change the generator from 240v to 120v?
Lin, if you have an older Kohler, odds are in your favor that you can configure it for a "center tap" to combine both for a single 120VAC output. It is usually pretty easy, the instructions are normally under the control panel.
SD
Quote from: Lin on June 13, 2018, 12:16:32 PM
Richard: Did you change the generator from 240v to 120v?
That's a trick question, right?
Our generator has two 30-amp breakers on the output. To be honest, I can't remember how it goes into the transfer switch without looking, and I can't do that right now as the bus is in the shop getting a/c work done. I'll get back to you with more details when I can look at the connections and/or the manual from Custom Coach, but I believe that each of the 30-amp outputs feeds one side of the load center. Our coach has two separate legs coming in from shore power, each powering one side of the load center as well. But, since our load center is a marine panel circa 1974 it is only set up for 120v - I don't think that it's even possible to install 240 breakers in the panel. We have electric heat running parallel to the LP, but it's all 120v. Same for our two-burner cook top and our hot water heater. All 120v.
I'll check on the connections with the generator and post again.
Quote from: solardude on June 13, 2018, 04:10:34 PM
Lin, if you have an older Kohler, odds are in your favor that you can configure it for a "center tap" to combine both for a single 120VAC output. It is usually pretty easy, the instructions are normally under the control panel.
SD
Lin if I remember correctly my old Kohler output had a jumper on the back of the 2 breakers that I removed to make it 240.
A busnut with bigger power needs, but all 120, can do both:
1) wire the generator for straight 120 for perfect balance on the windings, and
2) leave the coach wired with 2 sides in the panels, to access the required 50 amp power poles.
Having the correct bigger neutral sizing in the right places for this strategy is VERY important, as there is no balancing between the hots, the neutral will see ALL the power.
Beware of vendors... they have been the source of many busnut power problems, there are some who know less than you!!!!
But are great pretenders...
happy coaching!
buswarrior
Richard, I just checked and my unit is a Kohler L654, 7.5kw. Is that what you have?
Just thought I'd pass on this info for anyone with a 1970's Kohler generator that is thinking of changing it from 240v to 120v. I was able to track down an expert on these units. He was actually recommended to me by Kohler tech support who could not help. He is retired for their company and knows the old machines. Anyway, to be absolutely sure, one would have to know the model, spec, and serial number. But a rough rule of thumb would say if your unit does not have a starter motor, but is started by internal windings, it can not be switched over. Later models that have external starter motors can be. Since mine is the former type, that will not work.
His added advise was to never get rid of the unit. "If you do" he said, "you'll be sorry." He said that my generator was manufactured in July, 1979.
Quote from: Lin on June 14, 2018, 10:59:08 AM
Richard, I just checked and my unit is a Kohler L654, 7.5kw. Is that what you have?
No - we have a 12.5kw. Sounds like a different animal altogether. The bus is still in the shop awaiting parts for the a/c, but once it's home I'll check and see how ours is connected.