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Paul Dobbin 02-01-2008 03:51 PM

Dual Roof A/C Switch
A few months ago there was some discussion on this problem and I can no longer find the great solutions offered:
Problem: Two roof A/C units run on an alternating switch device that was supposed to keep our Land Yacht happy on a 30 Amp Service. It would not allow both to run together except on the generator. Ours never worked satisfactorily and after I worked on it, it didn't work at all. @##%^*
Somebody (maybe "Taxman") wrote that they had wired the second A/C unit to a seperate 20 amp plug and plugged it in seperatly in campgounds that
had seperate circuits on the same post. SOUNDS GOOD TO ME, but I can't find the post.
I would also like to know if I could plug that cord into my generator and still be able to use both on the generator power. (eliminating the need for the factory switching device)
If you have knowledge on this to share, please share it with me before the need for A/C becomes critical in the summer.

myfirstrv 02-01-2008 04:05 PM

Check out
"Fresh water enters power cable door on LY MH"
We started talking about the dual power supply at the end


Taxman 02-01-2008 10:48 PM


It was not me, and if you find the answer, please pm me -- I'd like to add that capability to my Land Yacht.

Thanks in advance.

lewster 02-02-2008 06:48 AM

This might help:

Since the neutral and ground are tied together at their respective buss bars, the only device you need is a single pole double throw switch of the proper rating that will send the hot voltage to either device......never both. This type of switch has the current entering at the center and directs it to what ever side the switch is positioned at, sending the current to one side or the other.

If you have the hot leads for both air conditioners at the breaker box, this would be the best place for this switch. It should be available at any well stocked electrical supply store.:D

raveson 02-02-2008 07:43 AM

Duel power on shore power
Contact Power Solutions

A couple of years ago I installed their product in my 89 345 for about $100.
Will allow you to continue to run both AC units while on gen and shore power.

Check it out, it works great!

jkcru 02-02-2008 08:54 AM

I had a similiar product from Camping World. It worked great, never had a problem. Be careful of plugging an extra cord into a power stand at an RV site as it may/most likely be on the same supply ckt. this may cause an under voltage situation and damage your elect. devices. I have run two A/C's on 30 amps with no problem by turning all other elect. devices off and starting the AC's one at a time.

blkmagikca 02-02-2008 09:31 PM

Paul, The two schematics dealing with the 30-amp to 50-amp conversion and the adapter box to connect 2 30-amp lines to the 50-amp plug have been uploaded at the following urls:

When you view them they will not look clear, but if you print them out they are quite legible (at least mine are using a LaserJet printer). The originals were done by my tech friend in pencil - he had promised to redo them in ink so that they would be a lot clearer, but hasn't yet.

The schematic niumbered 002 is the circuit as revised in the LY. The two dotted boxes represent the ATS switches (which consist of the DPDT relays and the time-delay relays). I found in my case that one of the time delay relays was not working, which prevented the circuit from closing so that the 2nd air conditioner would work. What threw me off was that the control circuits of the a/c's are on 12-volts, so that the power lights etc were lit up, but nothing was happening.

The time delay circuits are critical to this. It is necessary to ensure that before any load is placed on the generator, that it is running at full revs and that the voltage is at 110-115 volts. So there is a 60-second delay. There is an additional 60-second delay built into the a/c units as well, so that means that it will take 2 minutes after you start the generator until the a/c unit will actually switch on.

The schematic labelled 001 is the adapter box with a test circuit that will allow you to test the 30-amp circuits before you plug into them with the LY. It basically ensures that there is a common neutral to both 30-amp circuits.

Paul Dobbin 02-03-2008 12:39 PM

Thanks to all for quick answers. Now, I'll trace the wires for the existiing switch box back to the fire wall where they enter the breaker box. With all your help I should be able to get an electrician to guide me in making the conversion with out risk.
Thanks again,

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