Connecting Onan 5500 to Home Transfer Switch

[Chance]

Originally Posted by dkoldman

I think I am getting where you going. I have not looked at electrical panel inside of the RV. I think if I did this, I would need a 30 amp breaker to work with my existing transfer switch. But this would be a very costly option to run the 30 amp wiring from inside of RV to electrical compartment.

What I don't understand is how can I have a 7500 watt Transfer switch if it can only accept 30 amps? I was think 30 amps for each leg and with two legs it is total of 60 amps but max of 30 amps on each line?

If so; I think my plan was sound? But I am listening

Here is my transfer switch
https://www.amazon.com/EGS107501G2KI...99583010&psc=1

The switch you linked above is rated up to 30 Amps and 250 Volts maximum, hence yields theoretical maximum of 7,500 Watts. Normal (nominal) rating is 7,200 Watts (30 Amps X 240 Volts).

If you use one leg only, then you are limited to 30 Amps X 120 Volts or 3,600 Watts. Fortunately, a 3,500 Watt generator won’t exceed the Neutral’s current capacity. A 5,500 Watt can exceed 30 Amps (it can go up to 46 Amps maximum).

[dkoldman]

Originally Posted by Chance

The switch you linked above is rated up to 30 Amps and 250 Volts maximum, hence yields theoretical maximum of 7,500 Watts. Normal (nominal) rating is 7,200 Watts (30 Amps X 240 Volts).

If you use one leg only, then you are limited to 30 Amps X 120 Volts or 3,600 Watts. Fortunately, a 3,500 Watt generator won’t exceed the Neutral’s current capacity. A 5,500 Watt can exceed 30 Amps (it can go up to 46 Amps maximum).

So if I just use one leg and have it connected to X & Y on the receptacle, I will have exactly what I have had last 10 years with my portable generator. It was rare to ever trip a breaker.

I am thinking if I only use one leg, I will never go over 30 amps because the 30 amp breaker on the genny would trip?

This may sound like a bummer but it is really not for me. I just would like to safely be able to use my RV Gen to feed the house and not have to pull out the portable generator.

I plan to put the junction box and receptacle in the electrical bay. When we have been out of power; 30 amps seems like a lot and a blessing

[Chance]

Originally Posted by 16ACE27

L14-30 can handle up to 7500 watts at 240 VAC but only half that at 120 VAC even if you do have two hot because you only have 1 neutral leg. If the hot legs are not 180 degrees out of phase then the neutral carries all return current instead of just the unbalanced return current. I didn't even think about that until Chance's post above triggered my brain.

Sure would be nice if Onan built their generators to industry standard split-phase windings instead of in phase windings. I don't understand why they do that.

Just a guess, but I expect it’s easier to balance motorhome loads when L1 and L2 are combined. If kept separate due to 240V, I expect either leg could be overloaded somewhat easier when generators are smaller. Even at 5,500 Watts, that works out to 23 Amps X 240 Volts. Granted, generator breakers could still be 30A each side.

It can be done though. I saw a 6,000 Watt generator with 30A and 20A breakers, and it could do 240 Volts if I recall correctly.

[Chance]

Originally Posted by dkoldman

So if I just use one leg and have it connected to X & Y on the receptacle, I will have exactly what I have had last 10 years with my portable generator. It was rare to ever trip a breaker.

I am thinking if I only use one leg, I will never go over 30 amps because the 30 amp breaker on the genny would trip?

This may sound like a bummer but it is really not for me. I just would like to safely be able to use my RV Gen to feed the house and not have to pull out the portable generator.

I plan to put the junction box and receptacle in the electrical bay. When we have been out of power; 30 amps seems like a lot and a blessing

You really need to look at a schematic of generator and motorhome wiring. I have seen it before but would need to dig it up. The problem is that if Onan (or RV manufacturer) combine the two generator breakers, you “could” exceed current depending on how it is wired, and also depending on what you install. I would review the drawing first.

[16ACE27]

Originally Posted by Chance

Just a guess, but I expect it’s easier to balance motorhome loads when L1 and L2 are combined. If kept separate due to 240V, I expect either leg could be overloaded somewhat easier when generators are smaller. Even at 5,500 Watts, that works out to 23 Amps X 240 Volts. Granted, generator breakers could still be 30A each side.

It can be done though. I saw a 6,000 Watt generator with 30A and 20A breakers, and it could do 240 Volts if I recall correctly.

AFAIK they are not combined in a standard 50 amp RV panel. The neutrals are combined but L1 powers one side of the panel and L2 the other side, just like in a house except there are no double breakers for 240 VAC as the phases are in phase.

[dkoldman]

I found this on owner site.

All the Generator manual says is that the 30 amp breakers are per Line.

I assume power coming out of ATS is on the same line? At load center they do appear to branch off.

When I get a chance (pun is not intended) I will go to RV and flip a breaker off to see what L1 controls and L2 controls. If they are combined I assume I can get anything to work off one breaker as long as don't exceed 30 amps?

[Chance]

Originally Posted by 16ACE27

AFAIK they are not combined in a standard 50 amp RV panel. The neutrals are combined but L1 powers one side of the panel and L2 the other side, just like in a house except there are no double breakers for 240 VAC as the phases are in phase.

That is correct according to Onan drawing below. Each side (L1 and L2) is limited to 30 Amps anyway so having 240 Volts as you suggested would have made his project easier at up to full 5,500 Watts of power.
.

[Bill Johnson]

Originally Posted by dkoldman

I found this on owner site.

All the Generator manual says is that the 30 amp breakers are per Line.

I assume power coming out of ATS is on the same line? At load center they do appear to branch off.

When I get a chance (pun is not intended) I will go to RV and flip a breaker off to see what L1 controls and L2 controls. If they are combined I assume I can get anything to work off one breaker as long as don't exceed 30 amps?

I just talked to a Cummins/Onan tech and he said don't do it. He said it would be a floating ground and the chassis is basically the ground. If the wires are brought into the home it won't work right. If you decide that you're only going to pull off one side of the generator it will burn out the windings because of an unbalanced load. It wouldn't hurt to call them 800 286 6467 then 2 then 2. He did say they only have same phase in RV's and other applications unless that product has 240 used in the product

[16ACE27]

Originally Posted by Bill Johnson

I just talked to a Cummins/Onan tech and he said don't do it. He said it would be a floating ground and the chassis is basically the ground. If the wires are brought into the home it won't work right. If you decide that you're only going to pull off one side of the generator it will burn out the windings because of an unbalanced load. It wouldn't hurt to call them 800 286 6467 then 2 then 2. He did say they only have same phase in RV's and other applications unless that product has 240 used in the product

Well since the ground and neutral are bonded in the generator as well as in the house's main panel I don't see how he thinks it will be "floating".

But I do agree, don't pull of of one side of the generator, The right way to do it would be to wire a small sub-panel in with 15 amp breakers on each leg going to the receptacle for the house.

But now another thought has been triggered: Since the ground is essentially in parallel with the neutral in the connection from the MH to the house, is the overloaded neutral concern actually valid if the ground is the same gauge as the other wires?

[Bill Johnson]

Originally Posted by 16ACE27

Well since the ground and neutral are bonded in the generator as well as in the house's main panel I don't see how he thinks it will be "floating".

But I do agree, don't pull of of one side of the generator, The right way to do it would be to wire a small sub-panel in with 15 amp breakers on each leg going to the receptacle for the house.

But now another thought has been triggered: Since the ground is essentially in parallel with the neutral in the connection from the MH to the house, is the overloaded neutral concern actually valid if the ground is the same gauge as the other wires?

If it shows that there are 2 hot leads and a neutral. The generator is grounded to the chassis. If he runs a ground wire from the chassis to the ground in the panel wouldn't that take care of it. If the neutral/ground works in the RV at full capacity why wouldn't it work in the house?

[Chance]

Originally Posted by 16ACE27

Well since the ground and neutral are bonded in the generator as well as in the house's main panel I don't see how he thinks it will be "floating".

But I do agree, don't pull of of one side of the generator, The right way to do it would be to wire a small sub-panel in with 15 amp breakers on each leg going to the receptacle for the house.

But now another thought has been triggered: Since the ground is essentially in parallel with the neutral in the connection from the MH to the house, is the overloaded neutral concern actually valid if the ground is the same gauge as the other wires?

Two possible issues that would make me investigate or not do it at all. One is his panel at the house end. Within panel itself, do we know that current would be shared between neutral and ground?

Also a concern is that existing system (power cord) is designed for up to 60 Amps total through all conductors at a time. If used so that ground conductor aids with neutral current, total cumulative current through cord could be up to 120 Amps. That could cause overheating. In reality the generator is limited to 46 Amps continuous due in part to limited mechanical power so cord could see up to 92 Amps because of 120 Volts. I don’t think it is worth the risk.

One thing he might be able to do is power pool equipment from a stand-alone extension cord connected to the other motorhome circuit breaker circuit. His RV probably already has a 15A outside receptacle, and if that’s enough for pool pump (I have no idea), it may be easy to exceed 30A total. The house transfer switch could be on one Circuit Breaker and pool on other CB using separate power cord.

[Beau388]

Cummins Onan makes four different 5500 generators. The one most commonly installed in RVs is the QG Evap RV series. This generator has two parallel field cores, one of 30 amps and one of 20 amps. These fields are in phase. Cummins Onan does make a QG Evap 5500 in their commercial line that is 120v/240v capable. It is a 50 amp center tapped generator with 25 amps per phase.

Another story. When I built my shop, I tied the electrical supply into my home electrical system (60 amp split phase). I ran the under ground cables (two 04 awg and one 02 awg) thinking I would use the two 8 foot long grounds rods which grounded the steel structure (50 x 80 ft) as the system ground. Nope it won't go, as the house can only have one ground, so no master electrician would touch the main supply. So it was necessary for me to dig another 300 ft long trench and bury a UG 10 awg ground from the house to the shop to provide a common ground. That way I could get an electrician to pull the meter and hook up everything. My insurance company was happy and I was able to put the shop on my home insurance policy as an out building.

Going through the house load center meant I got a home electrical rate from WKRECC rather than paying an additional 30% more for a commercial rate. The transformer was a 50 KW (buried utilities 1,100 ft from the high line) on a pad about half way between the shop and the house so it would been cheaper to run the cables directly from the transformer and use the shops already installed grounds.

[16ACE27]

Originally Posted by Bill Johnson

If it shows that there are 2 hot leads and a neutral. The generator is grounded to the chassis. If he runs a ground wire from the chassis to the ground in the panel wouldn't that take care of it. If the neutral/ground works in the RV at full capacity why wouldn't it work in the house?

If "what" shows?

The generator has the neutral bonded to ground. There are 4 wires in 120/240 VAC connections but only 3 wires in straight 240 VAC connections (no neutral). There is always a ground wire.

[Bill Johnson]

Originally Posted by 16ACE27

If "what" shows?

The generator has the neutral bonded to ground. There are 4 wires in 120/240 VAC connections but only 3 wires in straight 240 VAC connections (no neutral). There is always a ground wire.

I was looking at this, of course I forgot about the ground in the 4 wire cord

[dkoldman]

Originally Posted by Bill Johnson

I just talked to a Cummins/Onan tech and he said don't do it. He said it would be a floating ground and the chassis is basically the ground. If the wires are brought into the home it won't work right. If you decide that you're only going to pull off one side of the generator it will burn out the windings because of an unbalanced load. It wouldn't hurt to call them 800 286 6467 then 2 then 2. He did say they only have same phase in RV's and other applications unless that product has 240 used in the product

Thanks, I will take this under advisement. My generator is my favorite toy, I don't want to damage it, but if I could use it more "that would be great"

I have the loads on the 10 circuits well balanced as that was part of my initial install. My current generator has 30amp @ 120 output that comes out of generator with one hot but merges two hots on the L14-30 cord. It has worked 10 years.

I only start going down this rathole because of what I learned from JamieGeek on F-150 EV. Seems like I should be able to do the same with my RV generator?

[dkoldman]

Originally Posted by 16ACE27

Well since the ground and neutral are bonded in the generator as well as in the house's main panel I don't see how he thinks it will be "floating".


I don't know what is happening technically, but I assume my existing portable generator is floating ground as I made a device to bond ground neutral together to fake my fancy smancy Southwire EMS out.


But I do agree, don't pull of of one side of the generator, The right way to do it would be to wire a small sub-panel in with 15 amp breakers on each leg going to the receptacle for the house.

I will kill the thought of wiring off one leg of 30 amp breaker. I think if I had to go with subpanel and two 15 amp breakers, I would lose power and could not run anything on the house that was on a 20 circuit. I have 4 20amp circuits on my Transfer switch. My 13 year old portable that I was about to put in the dumpster is slowly proving to be more valuable than I thought

But now another thought has been triggered: Since the ground is essentially in parallel with the neutral in the connection from the MH to the house, is the overloaded neutral concern actually valid if the ground is the same gauge as the other wires?

I really wish I could back to Plan 1 which is the wire both on L1 & L2 as 30 amps. I think all the wiring in L14 - 30 circuit can handle 30 amps. If that return Neutral is a push, I should be good. I doubt very seriously if I ever go over 30 amps but maybe a peak may see 35amps momentarily? I have never had a breaker in the transfer switch trip but occasionally I have had to reset the portable genny when it went over 30amps

[Chance]

For what it’s worth, F-150 Pro Power Onboard is 240 Volts on 30-Amp, 7,200 Watt units. That makes it quite different.

[dkoldman]

Originally Posted by Chance

Two possible issues that would make me investigate or not do it at all. One is his panel at the house end. Within panel itself, do we know that current would be shared between neutral and ground?

Also a concern is that existing system (power cord) is designed for up to 60 Amps total through all conductors at a time. If used so that ground conductor aids with neutral current, total cumulative current through cord could be up to 120 Amps. That could cause overheating. In reality the generator is limited to 46 Amps continuous due in part to limited mechanical power so cord could see up to 92 Amps because of 120 Volts. I don’t think it is worth the risk.

I don't follow, but I assume my cord can only handle 30 amps on L1 (X) and 30 amps L2 (Y) total of 60amps at 120 volts? If I go to 240 then half that for total of 30 amps? So with my limited knowledge, maybe the risk is with the neutral if it return 60amps? We saying 60 but I would think 35amps in total would be absolute max

One thing he might be able to do is power pool equipment from a stand-alone extension cord connected to the other motorhome circuit breaker circuit. His RV probably already has a 15A outside receptacle, and if that’s enough for pool pump (I have no idea), it may be easy to exceed 30A total. The house transfer switch could be on one Circuit Breaker and pool on other CB using separate power cord.

I have given up on doing anything with the pool equipment. It is 240 and on an existing Double pole 20amp breaker. It has Heater and two pool pumps I have learned how to drain the new heater and if we get that bad again in Texas, I will shut the entire pool down and drain. Last February when I learned I really needed to drain; it was too late as everything was frozen already and it never rose above freezing to thaw out to drain.

Well I got a brand new L14-30R Receptacle and no where to put it

[dkoldman]

Originally Posted by Chance

For what it’s worth, F-150 Pro Power Onboard is 240 Volts on 30-Amp, 7,200 Watt units. That makes it quite different.

Yeah but to get an F-150; then that mean you would haver to buy a Truck &$#@! What on earth would I do with a Truck here in Texas

But that 240 Volts on 30-Amp, 7,200 Watt units is almost the exact specs my Transfer Switch calls for. I assume if I had that 240 it will still do 120vac unless you double pole 2 breakers together to get the 240?

[dkoldman]

Couple of things I found this morning.

This was from a Graduate student about 10 years ago...

Marlow is correct - an L14-30 is a 30A 240V cable - you get 30A at 240V with a neutral plus ground. You can use 30A X 2 for line to neutral loads, giving you "60 amps" at 120V, but this is still really a 30A circuit.

And here is article on wiring for L14 - 30

https://www.hunker.com/12445679/how-...ma-l14-30-plug

The key points from the article I saw were....

1. The cable to which you attach a 30-amp twist lock plug has to be a minimum of 10 AWG, which is one size larger than standard 120-volt residential cable.
2. Because the 10-gauge wire is a little beefier than 120-volt cable, it's more difficult to twist around terminal screws

The way I see it is basically the wired is designed for 240 and 30 amps, but if you only send 120v then you actually have more capacity in the wiring but still limited to 30 amps on each leg.

The reality is at most I may use 20 amps / leg and that would basically be with every thing including the kitchen sink on, which is never the case.

When I bought the the l14-30 adapter for my old generator I recall it saying that the L5-30 on in was maxed at 3750 watts whereas the L14-30 was maxed at 7500 so that must me each Hot leg has 3750 and the neutral wire is what it is and has to be able to handle?

Trying to think this through, because I have not started it anything yet. Just some sunk cost in electrical parts.