Need suggestions on 110 volt for a trailer

belfert · March 27, 2011, 05:09:18 PM

I have a 20 foot enclosed trailer I want to use as sort of a shop when I'm at a rocket launch so we can prep rockets inside and have 110 volt power for tools and for a roof air.

The 110 volt will come from the bus. The bus has both a generator and an inverter. The bus has a 30 amp buddy outlet for another RV that only gets generator power. The 30 amp RV outlet would great except we want to use inverter power without air conditioning when the generator is not running. What I don't want to happen is to have someone turn on the A/C in the trailer when the bus generator isn't running and kill the bus house batteries. The bus also has regular 110 volt outlets on the outside powered by the inverter.

Any thoughts on how I lock out the air conditioner in the trailer when running on inverter only? The other issue is the 30 amp RV outlet has no power on inverter. I'm thinking I have to run two cords to the trailer and maybe use a transfer switch. I would prefer not to get that complicated.

My friends simply are not going to think about the generator not running and will just turn on the A/C in the trailer if they are hot. The air conditioner will run for maybe 30 minutes until the inverter in the bus shuts off due to low battery voltage.

fe2_o3 · March 27, 2011, 05:19:26 PM

Breaker box in the trailer. Shut off the a/c breaker when on inverter. I don't think your friends would search for that with out telling you.. Then again??...Cable

belfert · March 27, 2011, 05:47:07 PM

I'm not a babysitter. I would rather not have to remember to shut off a breaker in the trailer every time the generator is shut off.

One new idea I came up with is installing two breaker panels. One small one for A/C and another for all other 110 volt circuits. It would still require two cords to the bus which I would like to avoid.

gus · March 27, 2011, 08:25:48 PM

You can run a wire from the large box to a smaller one inside the trailer and use that for a switch.

My two ACs are on separate boxes, one small, but mostly because my Honda gen has two output coils.

RJ · March 27, 2011, 11:56:54 PM

Brian -

Does your generator have an auto-start feature that kicks it on when the house battery voltage drops to a certain point?

If it does, that's one solution - just plug the trailer into the coach house system.

But, IMHO, you'd be better off with the trailer being totally independent of the coach. Buy a little Honda EV3000 and a couple extra jerry cans for fuel and be done with it. Put it in a lockbox on the tongue so it doesn't grow legs and walk off.

If buddies want A/C, they can fire up the Honda.

KISS principle!

FWIW & HTH. . .

belfert · March 28, 2011, 05:25:52 AM

I am hoping to do this at minimal cost. One of my friends does have a Honda EU3000 that maybe he would bring. It seems a little silly to run a generator 15 hours a day just for lights and a few tools when the air conditioner isn't needed. I already have an underutilized generator in the bus.

The bus generator has auto start, but the inverter does not do auto start. One of the other issues with passing the 30 amp RV outlet through my inverter is that one of the bus A/C units already goes through the inverter. I could end up overloading that 30 amp circuit with two A/C units running.

Busted Knuckle · March 28, 2011, 05:37:34 AM

Brian,
I'm with RJ on this one.
You've spent tons of time and $ on your bus Z(& now a trailer) to use when you guys go out west for the Rockets.
But really just how much time or $ have ANY of these other guys contributed to the cause with you?

Just set the trailer up to have A/C and power run from a generator on the tongue, and tell them if they want power in the trailer they need to bring a generator for it.

Then in a worst case scenario if they won't bring a generator you can run a simple extension cord to the trailer for lights.

Personally if it were FOR ME (which it ain't) I'd have it set up to run off the bus generator only and be able to use the A/C anytime I was in it! (trailers are not well insulated, and it's hot in the desert in the summer!)

BK

belfert · March 28, 2011, 08:23:20 AM

I don't actually own the trailer anymore. I sold it to one of the other guys. I did volunteer to do the electrical in the trailer as I have a bunch of the necessary parts and another guy in the group has parts too.

Surprisingly, we don't use air conditioning every day in the desert. It is starting to cool down by late September. We didn't use the air conditioners in the rental trailer last year because we didn't have any way to hook up power. It also wasn't really warm enough to need the A/C either.

It just doesn't make much sense to run a second generator when I have one in the bus that is never fully loaded.

One of my friends did go out and buy a new travel trailer a few years back. He tows it with a 10 year old one ton conversion van with a 454. He did haul it to Reno with us one year as we had a total of 12 people. That van doesn't have enough power to haul the trailer through the rockies very well. The van even lost a cylinder on the way home. He is the one who has a Honda EU300 generator.

Len Silva · March 28, 2011, 09:14:09 AM

You can do it easy enough but the complications may not be worth it.

You could use a relay in the bus operated only when the generator is running, perhaps powered from the generator side of the transfer switch. Using low voltage (12 or 24, as available), use this relay to operate a second contactor in the trailer to operate the air conditioner.

The disadvantage to that setup is 1.) A second pair of wires between the bus and trailer, and 2.) Now the trailer AC will not operate at all away from the bus without additional complications.

Lin · March 28, 2011, 10:21:08 AM

Two ways I see are a relay system that powers the AC when the generator is on, and a two cord system where one cord just connects the AC and the generator. I would go with the two cord system first since it requires next to nothing in cost and labor. You can always upgrade later.

robertglines1 · March 28, 2011, 10:33:17 AM

Maybe trailer needs it's own separate inverter system.Modified sign wave would probably do. And a separate small gen set for air. That way it could be used with or without bus in attendance.

belfert · March 28, 2011, 10:46:32 AM

I would rather run two cords from the trailer than duplicate the battery, inverter, and generator setup the bus already. I may not own the trailer anymore, but the current owner doesn't have a vehicle to tow it. The whole intent is to hook the trailer to the bus when it is used.

It would be less expensive to just run a seperate generator 15 hours a day than to buy an inverter and batteries plus a generator for the trailer. The trailer might need 110 volt power a whole 7 days a year.

JackConrad · March 28, 2011, 12:55:28 PM

Brian,
It would take 2 cords, but you could run a cord from the generator supplied buddy plug that would feed only the AC, and another cord from the inverter for all other 120 AC uses. This would definitely stop anyone from running the AC off the inverter sand would eliminate any transfer switches. Jack

belfert · March 28, 2011, 01:41:49 PM

Quote from: JackConrad on March 28, 2011, 12:55:28 PM
It would take 2 cords, but you could run a cord from the generator supplied buddy plug that would feed only the AC, and another cord from the inverter for all other 120 AC uses. This would definitely stop anyone from running the AC off the inverter sand would eliminate any transfer switches. Jack

This is what I am leaning towards as even a transfer switch wouldn't help like I thought it would. I could also wire some outlets to the 30 amp in case someone wants to run more stuff than 20 amps will allow. One issue would be the cost of wire, but I think my friend might have the wire.