Change voltage Onan Gen

[larrypride]

I have a 5,500 watt Onan generator that makes 120 volts. 2 legs of 120 volts. I called Onan Cummings and they said I can change gen to make 120/240. My question is why is the trailer a 2018 Voltage, wired for 2- 120 volt legs? I'm wanting to change the voltage to I can run my house when I loose power and 240 would be easier to connect to house panel. I'm and electrician and I don't get this.

[wildwest450]

The 50-amp 120/240-volt 3 pole 4

[larrypride]

Originally Posted by wildwest450

The 50-amp 120/240-volt 3 pole 4

I know all about 50 amp services and Receptacles My question is why did Dutchman wire it this way?

[ATCguy]

Ok, I'm no electrical guru... far, far from it. But it's my understanding that putting 240 into the RV will blow most of the components in it. Ergo, two separate 120 legs.

I'm sure Sundancer and/or Wahoo will chip in later whenever they see this thread. It seems they've answered this (or similar) question before... and their answers could probably be found by doing a search.

[sundancer 87]

A basic 'why' is because we don't have anything in the RVs that use 220 VAC. No clothes dryers, ovens, A/Cs or water heaters.
With two 110 volt legs the 110 volt stuff can be separated between the legs.

The inverter or water heater or vacuum or A/C or fireplace or furnace or whatever can be grouped but on individual 110 volt legs.
Another thing to consider, camp grounds with 30 amp service. With the 30 amp service not all appliances can be used simultaneously as with the 220 volt 50 amp service. So one leg to service a limited amount of appliances.

Then we have also have the ability to use 110 volt 20 amp for minimal appliance use.

[larrypride]

Originally Posted by ATCguy

Ok, I'm no electrical guru... far, far from it. But it's my understanding that putting 240 into the RV will blow most of the components in it. Ergo, two separate 120 legs.

I'm sure Sundancer and/or Wahoo will chip in later whenever they see this thread. It seems they've answered this (or similar) question before... and their answers could probably be found by doing a search.

ATC guy where do you ATC? I instruct at KMYF. I’m still trying to figure the question. If you use your 50amp service it will be 230 volts, and if you put 50amps on each leg on the same phase you could get 100 amps on neutral. That would fry the neutral. I was looking at my gen last week and the neutral appears to be the same size as the hot conductors.

[larrypride]

If you have 2 hot legs on the same phase the neutral will carry the load of both circuits. You could overload the neutral. I would prefer that my unit is wired just like a home. There must be a reason they did that. I will check maybe the neutral wire is bigger?

[ATCguy]

Originally Posted by larrypride

ATC guy where do you ATC? I instruct at KMYF...

I'm retired now. 8 years of USMC controlling (including a couple years just north of you up at NFG back in the early 80s), and then 23 more with the FAA. Finished up my last 16 years at New York Approach (N90).

[persistent]

On the TT side, the answers are in the TT wiring diagram. There are issues with transfer switches and multiple possible sources of power. They are all different and require different configurations to hook up. I don't know about your particular TT, but some RV's get highly complicated. Transfer switches are designed to manage all that.

On the power source side: 230 volt AC is two legs with a common neutral. The two legs are "out of phase" (one leg is high while the other is low). The neutral caries only the difference in load between the two legs.

L1 may carry 20 amps while L2 is carrying 15 amps. The difference (5 amps) is carried by the neutral. You cannot overload the neutral. Some outlets are powered by L1 and others by L2. Any 230 volt appliances would have to be separately wire between L1 and L2.

Many big generators and inverters provide only 115 volts. Also, when connected to a 30 amp pedestal you only have one leg 115 volt to work with. The transfer switch connects both TT L1 and L2 to the generator or inverter so all outlets are powered.

When you have a two leg 230 volt generator, you don't need the transfer switch to reconfigure the TT, so you would need a different transfer switch or a transfer switch which could be reconfigured to match the two leg 230 volt generator. The switch would still need to accommodate the one leg inverter.

With the proper transfer switch and TT wiring, you can do anything. It may cost quit a bit.

[KN5DX]

Hi. I see several different questions asked and some partial answers.

To the OP: Dutchmen wired this way due to industry standards. ONAN is the gen manufacturer, they wired the internal windings to produce 2 separate 120v phases 120 degrees apart from each other. Much like a 3 phase motor produces 3 separate phases each 120 degrees apart.

There basically ends up being dead / hidden phase. More common in the EU as it relates to getting a motor to rotate the proper direction. It is done for emergencies on HV transmission and distribution lines in an open delta config here in the US. Usually 1/3 transformers down, no replacement.

The RV distribution side is really 2 independent 120v services to load balance. There is no "240v" (line to line) equipment installed. A typical home is 2 separate 120v service with ability to wire line to line for 240v equipment.

An RV transfer switch does not connect L1/L2 internally to genset. It switches both like a motor across the line starter.

While you can have ONAN re-configure the windings the downside is you will lose around 15% (maybe more) of your capacity. Basically derating your genset drastically.

My personal solution is : house power out, I fire RV UP and wait.