installing onan 4k in 50 amp 2015 Puma Unleashed

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rbTN

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Hello all,

have a generator question, or more of a how to wire it question..

My son has purchased a newer TH, 2015 puma unleashed. It is supposed to have the generator prep option (no generator has been installed) and he wants to move the onan 4k from his old TH to this newer one.

I've not looked at it, and he has only briefly but I have searched for and not found an answer to wiring it up. I know he needs to add a transfer switch etc, but my question is with a gen set that is 3 wire, how do you connect it properly to a 4 wire 50 amp system. Do you combine both the L1 and L2 on the trailer side and connect to the hot from the generator? It seems that is the only way an adapter would work to go from a 30 to a 50 so kindof makes sense?

and if anyone happens to have the same unit, where does your wiring from the generator connect to the trailer. He said there is no junction box in the compartment for the generator?

thanks!
 
Yes. That's what an adapter will do. It combines both circuits in the RV so that the RV can be powered by 1 axillary circuit. This is ordinarily done as a temporary wiring condition if a 50amp service isn't available at a camping area.

Your situation is a permanent adaption of the generator which makes it a little complicated. If you combine both L1 and L2 at the generator, there must be a switch to release that combination back to 2 separate circuits when you plug into a 50 amp pedestal. This could be done in the form of a transfer switch. I personally do not have experience with that specific wiring design. Hopefully another member can be of assistance.
 
A transfer switch will work.  So will mounting a 50 amp outlet in the shore power cord compartment if the shore piwer cord is permanently attached, then plugging the cord into that outlet when you want generator power.

The technical details for either option are Line 1 and Line 2 on the generator input to the transfer switch or on the 50 amp outlet are connected together to the generator's single 120 volt circuit breaker.  Neutral and ground are connected normally.

Normally this is frowned apon, because with a source capable of delivering the full 50 amps on both legs, the neutral can be overloaded.  This is not a factor with a 4000 watt generator because even at it's maximum output it will not overload the neutral.

One caution is if he has any 240 volt appliances in the RV, they will be energized with a hidden shock hazard on internal parts when running on the generator.

The hidden shock hazard is the internal parts of a 240 volt device will be at 120 volts above ground, even though the unit appears to be de-energized and inoperative because there's 0 volts, not 240 volts, from one hot leg to the other.
 
thank Henry and Lou - yes I told him he will need a transfer switch and he is getting one. I will ask him to confirm he does not have and 240v appliances before hand so he does not get into a dangerous situation.
 
Are you aware of any stock RVs using a design like this?
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It used to be quite common and I suspect it still is on trailers.  Heck, I had a 2002 Class A motorhome that had no transfer switch - just a 50A plug connected to the generator.  A automatic transfer switch is a convenience in a motorhome where you might want to crank up the genset while underway, but for a trailer where you are gong to be stopped anyway, plugging into the genset is simple and easy.  I wouldn't bother with a transfer switch in this case.

If there is no wiring in place, it's not clear what the generator prep package provided.  It won't have fuel supply or exhaust system cause those need to be custom for the genset used.  He will likely find wires stashed somewhere up there.  Exhaust and ventilation are much more a concern (and maybe a challenge) than electrical hook-up.
 
I would suggest using the plug method instead of a transfer switch. It is quite possible he already has the 50 amp cord in the trailer now. That cord would either plug into the shore power pedestal or into a 50 to 30 amp adapter to the generator. That works just fine and makes things much easier to install.

I also would recommend to keep the generator power plug a 30 amp outlet and use an adapter so that there isn't any confusion of the available power.
 
Henry, its funny you posted that this morning. We were talking yesterday afternoon and he is decided to mount a 30amp plug in the compartment and just plug into it. That will also allow him to power other things if he does not need it in the trailer.

thanks for the help
 
I'd install a 50A outlet instead of 30A.  30A is a max of 3600 watts and the outlet will get hot if run for 30+ minutes at 2900+ (24 amps).  A 50A outlet will carry the max output of the Onan 4000 and stay cool doing it. Just tie the single hot from the genset to both of the hot terminals in the 50A outlet. A small side benefit is that he won't need a 50/30 adapter to plug in.
 
Probably correct but I wouldn't change the wiring in a 50 amp outlet and create a new hazard. A 30 amp outlet is the correct outlet for the 4000 watt generator. My Onan Microquiet 4000 uses the 30 amp outlet and shows no signs of any heat damage 18 years later.
 
I wouldn't change the wiring in a 50 amp outlet and create a new hazard.
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In what way does it "create a hazard"?  The internal wiring would be exactly the same as the standard 30A-->50A adapter (dogbone) used to plug a 50A RV into a home 15A outlet.  Is that hazardous to do?.

My Onan Microquiet 4000 uses the 30 amp outlet and shows no signs of any heat damage 18 years later.
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Irrelevant, since you haven't told us the wattage you routinely draw. If you rarely exceed 2000-2500 watts, of course there is no sign of heat damage.  But pull 3500-4000 watts for 30-45 minutes and then feel the plug.
 
Lou explained one of the hazards very well in his post. Another hazard would be that the control circuits of a 220 volt device would also be powered as most of the time only requiring 110 volts. Using an adapter does create the same condition but it comes with a red flag that would not be there if an unsuspecting person plugged into a compromised outlet. For safety, outlets should always be wired as approved and adapters should be used with an understanding caution. The poster also mentioned that he may use the generator for other functions so now the issue becomes even bigger and signals another concern.

I don't disagree with your intentions but wouldn't recommend the modification you suggest. I do recommend the use of an approved adapter.

There are many factors that would be in the equation to determine an outlets temperature at a given load. Too many to list and I won't get into it but as I stated previously, I don't disagree with your intentions but I would not recommend incorrectly wiring a 220 volt 50 amp outlet to correct your calculations. The 30 amp outlet is standard for this installation and should be followed.




 
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