Air conditioning electrical advice requested please...

[miles2go]

I have two Dometic (Duotherm) rooftop a/c units. Old ones, circa 1994, model numbers 610015. I only have one touch pad. Here is a picture of the touch pad. It is a touch pad controller with the functions you see listed on the face. It works great. Nice cold air. Both work great, they seem like new. Bought at a government auction and had been on a shelf for years. But I can only control one a/c at a time, by unplugging the touch pad and moving it I can control the other a/c unit, again only one at a time.

I think that someone told me previously one touch pad will not run both a/c units at once no matter how I connect it. I have searched high and low, no other touch pads can I find. Dometic says they were discontinued. These are units before they ran 12v. to the controller, all 110 ac. So in the next post down I will put a pic of what may work if the consensus is right. Sorry you have to read the pic backwards.

[miles2go]

These are pics of a plain Jane a/c switch salvaged off an even older unit. Well this is the front, below is the important rear for the wires.

[miles2go]

Ok, here is the rear and my question, wait, I have to show a pic of the controller in the unit first... in the next post...
But while looking at this one note the copper temperature sensing wire, where should this be positioned? I was going to mount this rotary switch away from the unit for easier access. Whatever this is supposed to sense is probably up in the unit right?

[miles2go]

Ok. If I remove the wires from the controller, up in the left hand corner. The yellow is the medium fan speed, the red is the low fan speed, the black is the high fan speed, and the brown is the compressor. If I attach the wires from the thermostat in the older rotary style switch above, namely the brown to compressor brown, the low fan red to red, the medium fan speed yellow to the tannish center position off of the rotary switch that corresponds to the medium setting, and the high black to black (high), then connect 120v black and neutral to the corresponding wires on the old rotary switch. Will it work? I'll post the wiring schematics next. The ribbon connector in the top right is where the touch pad should connect... but I don't have a touch pad, sigh.

[miles2go]

Here is the a/c schematic of the units I have.

[miles2go]

Here is the a/c schematic from the system the old rotary switch came from that I want to use in place of the controller and touch pad. Will doing it this way and bypassing the controller with the older rotary switch fry anything?

[PCC]

I know Sean will have ideas for this one, but my idea would be to make the second unit a slave, delayed, from the first unit. It senses the start of the first unit, and, after a timer circuit, starts number 2.

Shutting down can be done together, but it would be the startup that would be hardest on the available power, whether shore, genset, or inverter.

Those would be my thoughts, and not that difficult to do.

Keith
PCC

[miles2go]

Thanks Keith, but my electrical knowledge is so limited I would not know how to make the second unit a slave. This solution I posted was not my idea, I am not that electrically competent. but I did want to check with all to see if it would work... I am open, very open to better ways to do this. I dislike giving up the touchpad functions, but anything that will work as long as someone advises how.

[RTS/Daytona]

here's a simple - cheap solution -

add an inexpensive digital thermostat available from walmarts and lowes etc

see--> http://www.klenger.net/RV_General/HVAC_Hunter_Tstat/index.html

pete RTS/Daytona

[miles2go]

I don't have 12v dc and that solution requires it. I could add a converter to take the 24v and provide 12v, but then all the 110v controls are run by 12v? Is it this simple to just put a Hunter thermostat in there. That link is great. I'll read some more. Thanks. I have three fan speeds, and no 12v, I am not sure the hunter thermostat will work.

[belfert]

The problem with just adding a regular thermostat to these old Dometics is the Dometic doesn't have the right controls to accept a regular thermostat.  My understanding is the system is completely proprietary.

I see posts in other RV forums all the time from people looking for these obsolete control panels as the A/C won't operate without them.

[James77MCI8]

What is the control voltage for the key pad?

[miles2go]

It is 110v. "These are units before they ran 12v. to the controller, all 110 ac." Well, maybe not.

[James77MCI8]

The schematic says this is low voltage. I don't think the controller is 110. Call me 864-592-2346

[James77MCI8]

The touch pad is a low voltage interface for the control board. As long as the rotary switches are rated for the current load your scenario should work.