I started working on the "command center" last Monday and I thought I would share what I found. The center was originaly equipped with two 7kw onan gen sets, each producing 220vac. I found that the 240 volt was required for a very large heat pump that originaly was mounted on the rear of the coach. Each generator fed a dedicated 6 circuit electrical panel with 220. The only appliance requiring the voltage was the heat pump, and since I learned that all is really needed in the commands centers "new" lease in life is single phase power I proceeded to re-wire this bugger so it can be plugged into a normal campground outlet. I also know that the second phase of generators is usually used for the second rooftop A/C ( which the command center does have) so there is some wiring that needs to re-routed and configured as such. Here is a couple pictures of how this rig was originaly wired, I will continue with another note of how the wiring has been updated in another post. I thought this post may help someone else that purchases a similar unit...but I believe this critter is one-of-a-kind....

Here is another picture of the wiring within the shore-power cabinet. The prior owner had wired in one of the four possible 120v circuits to a 30a campground plug....plus they had the hot and neutral reversed, a accident waiting to happen...

It must have been something when it was up and running!

The wiring that is reversed is not real clear in this photo, but in residental and commercial line voltage wiring the black wire is hot and the while wire is the grounded conductor....
Folks that don't understand this need to hire an electrician, or someone can be hurt.

All coaches wired for 50 amp service use 240 volt, 3-pole, 4-wire power cords. This configuration nets 100 amps 50 per leg with 120 or 240 available.

I also also noticed in this last photo, there are loose wires going through a romex connector. DO NOT LEAVE THIS AS IS. Use seal-tite conduit or something similar to properly run these wires, or replace them with 10/3 w/g Romex.

Good luck with your conversion! A Labor of Love !

Billy T

I would caution anyone working on something like this to check EVERY inch of every wire for proper installation and color coding. There is too much at stake to trust the last five guys (whoever they are) that worked on it.

Older stuff with a history needs this, and this goes double for non-standard stuff.

I agree with bill h. One redneck-engineered connection is a clue that there may be many. Each conductor needs to be traced for wierdness, (Fourth Rule of Electricians) "Lest thy maker see fit to end thy tour upon this Earthly Vale of Tears, and thine Friends see fit to comfort thine widow in way unacceptable to thee."

While improper wiring in a plastic pig might take years to show up, an all-metal motorhome like a Barth has potentially lethal consequences for a wiring error.

"All coaches wired for 50 amp service use 240 volt, 3-pole, 4-wire power cords. This configuration nets 100 amps 50 per leg with 120 or 240 available."
Note: This is, of course, SINGLE PHASE 240/2P/4W power; black and red are hot, white is neutral, green is ground. 3-Pole denotes 3-phase power, which campgrounds do not supply (although 3-phase may be run throughout the camp as a supply vehicle for the single-phase). Please correct me if I'm wrong on this.

Yes that is correct. 240VAC is actually two single phase circuits that are 180 degrees out of phase.

I have found on my SOB that the units generator determined how the unit is wired. The Onan I have is a 6.5kW, with two circuits. One of the two is a 30amp and the second is a 20 amp feed that is dedicated to one of the two Rooftop air conditioners. I am not sure if the two circuits are 180degrees out of phase, and it does not affect the use of the RV since I have no 240VAC appliances. I could start it up and check to voltage to see if it is 240VAC or 0.

The original wiring on my SOB used only a single 30 amp cord. When plugged to shore power only one of the A/C units could be used, unless the generator was started. This was not acceptable for us since we have camped in the heat and plan on taking g-child, so I could not leave her in the front of a hot camper or let her take a nap in the back without A/C. I have to note that our SOB had two switches that allows the user to select which of the two A/C units is allowed to run on shore power.

So, my solution was to convert to 50 cord. The way I did this was to add fused disconnect, known as a pull-out. These are used on most residential air conditioner units. I fused one of the two circuits at 30 amps, the other at 20 amps. From the pull-out I installed a automated relay box that allows the transfer of power between the generator and shore power. I then had to pull the dedicated 20amp power circuit from A/C selection switch panel to the output of the transfer switch. I then pulled the power from the generator to the appropriate transfer box input. Note that the generator has two circuit breakers, one is a 20 amp, the other is 30.

Now, I can plug into a campground power and run either A/C unit. I also bought a 50a to 30a cord. So I can plug up at campgrounds with 30a only. I know when I do this that I can only run one A/C unit.

After I did all this I learned another way of accomplish the same thing, which is what I plan on doing to the command center. The command center, like my SOB, does not have a transfer switch. If you want to use the generator you simply plug the shore power line into a 30 amp receptacle dedicated to the generator, located in a cabinet. The next best thing is to pull the generators second circuit to the same cabinet and wire it to a 20amp receptacle, then add an 20 amp extension cord to the second A/C unit and plug it into the receptacle located in the cabinet when you desire to run both A/C units on the generator. This also allows the camper to operate both A/C units at some campground sites because the 120v receptacle is likely a separate circuit than the 30 amp. You simply plug in both cords and everything works! this is actually a better solution than the transfer switch, and cheaper too.

I thought I would add this for anyone interested in upgrading there service to allow the use of two A/C units. 240vac is not needed unless you have appliances that use 240.

"Three pole" is a useable description, although technically, it's "two pole", as the neutral isn't counted. "Three-phase", which is almost always 440 VAC, is very expensive to connect, and is never used to supply 120/240 VAC mains (440/3 operates with each leg 120° out-of phase; 120/240 is 180° out-of-phase). The expense arises mostly from the need to run a new set of mains to the user, as 440/3 can't use the standard conductors.

The larger gensets usually are 240 VAC, with two 180° out-of phase 120 VAC legs, the same as the 50A outlet at RV parks.

Larger (50A rated) Motorhomes are wired the same way a house is - two 120 VAC legs, except that in most cases, connecting across the two hot legs for 240 VAC is rare. When a 30A adaptor is used, only one 120VAC leg is hot - anything wired to the other, 20A leg is dead; that's why only an A/C is connected to that circuit. Some coaches have an A/C transfer switch so that either, but not both, A/Cs can be run from the 30A circuit.

As billyt53 noted, the terminal clamps in the pictured junction box are not watertight. But neither is the junction box - both the clamps and the box should be replaced with PVC watertight ones. It's also a good idea to put a dab of De-Ox or other appropriate grease in the wire nut before screwing onto the wires. In no case should 120VAC wire nuts be left exposed - all should be in boxes.

One thing that is VERY important in motorhomes is the integrity of the ground circuit; in most houses, the neutral is the center tap of the pole transformer, and ground is an additional physical connection the the Earth itself. If there is a problem in shore power wiring, someone touching the coach could provide the path to ground.

Amazingly, when I moved the meter can on my house (which had previously been owned by an electrician and then a generator operator), there was NO bonding strap to Earth!

Anyway, replacing that junction box and the terminal clamps can be left for Mary Ray .

Rusty, you rascal you, how did you know that I work for one of the largest electrical contractors in the city of Memphis. A smile and a big batch of nanna pudding will work miracles on electricians, especially the single ones that don't have much home cooking.

Beer is good, too!

I save the beer for really difficult jobs

That's good, cause there are a couple beer quality jobs left in the rear of this coach!


I found that the 12v wiring had been modified, so I put it back so the refig will not use the chassis battery for power. this would have definitely caused a no-start condition after a couple days of sitting since the convertor dose not connect to teh chassis battery.

She starts a lot better with fresh plugs and wires. The exhaust leak is better, air and fuel cleaners are changed, tires on the front now have tread on them, brake has fluid, convertor converts, belts are tight and I will pick up bolts for the seats and belts today...it seems that one of the prior owners only thought it needed a couple bolts in each seat...and they were loose. It was kinda "wobbly" going up the road last April.

I'm gonna miss her when she is gone....

BTW, there is a switch on the dash marked "stobes" I learned that it flashes the headlights continuously...that will get your attention.

Gee, it is nice to have my own personal mechanic that gives me frequent progress updates. He also travels with me as a rolling pit man, what a deal.

quote:

BTW, there is a switch on the dash marked "stobes" I learned that it flashes the headlights continuously...that will get your attention.

Kind of a shame they removed the sirens and the blue lights...