RecPro AC hp & function of furnace

[Ron C]

Earlier today, I posted this help request to the wrong form. Sorry . . .

Just copied my post here in hope some one might have an idea to assist.



new RecPro AC hp & furnace control prob
Hi

I need some “sage advice”.

I purchased a new RecPro 15k AC heat pump to replace my 12 y old Dometic 15k AC with DuoTherm Comfort Zone thermostat.

I was looking forward to the efficient, quiet new model and its head for the Spring & Fall.

I thought that its remote control system would make the install easy.

However! The Atwood furnace has control wiring which comes from the Dometic AC control box in the ceiling unit. When I install the RecPro, I will lose the ability to control my furnace. Not a good outcome.

Has anyone out there face this problem and come up with a solution? I would greatly appreciate any advice or suggestions you may have!

I no longer need to keep the DuoTherm thermostat controls for the AC or fan and am even game to retire power to the furnace and attach wires to its blue thermostat wires up to a new single function mechanical thermostat operating on 12V.

What do you think is the right way to handle this?

All the best!

Ron C
2011 Montana 2955RL

[Ron C]

I’m going to try removing the old Dometic AC, but detaching the control box somewhere out of the way. It will need the communication wires snapped in and possibly the 12v supply, but I figure the 120 v supply side can be removed. I should also remove anything that was going to the top side of the old AC.

If I can get enough play in the wires, I will try to recess it into a side wall as best I can and seal it. I will need to leave unobstructed space for the new AC HP as possible.

I am hopeful that will work to leave my furnace controls the same. If anyone out there has done this successfully, I’d appreciate hearing how you made out.

Thanks.

Ron C

[Lee-CI]

Ron I'd help out if I could, but this one isn't in my wheelhouse. I'll re-read your posts again after my coffee kicks in. Good luck and let us know how you come out.

[prndl]

There is an installation manual for Atwood Furnace in this forums Files section. Look at page 5 for the wiring diagram. Does not look like there is any reason you can't just connect the furnace to a thermostat without the A/C control box. The A/C interface actually does not appear in the installation manual diagram. At least I did not see it.

[Ron C]

PRNDL
Thank you for the info. I will check out this page.

I know the furnace in basic trailer systems often have a single separate thermo switch that has its two (usually blue) wires directly from the furnace . . . simple and direct.

The problem is that in the Dometic AC and DuoTherm system, the furnace controls are fed to and through the AC control box in the ceiling unit. Why? I know non-Dometic don’t. I also am not sure where the 12V supply for the furnace come from, hopefully not from the old control box.

I guess all will be revealed after the wires are cut. ��

All the best

[Bourbon County]

Originally Posted by Ron C

PRNDL
Thank you for the info. I will check out this page.

I know the furnace in basic trailer systems often have a single separate thermo switch that has its two (usually blue) wires directly from the furnace . . . simple and direct.

The problem is that in the Dometic AC and DuoTherm system, the furnace controls are fed to and through the AC control box in the ceiling unit. Why? I know non-Dometic don’t. I also am not sure where the 12V supply for the furnace come from, hopefully not from the old control box.

I guess all will be revealed after the wires are cut. ��

All the best

I believe they do that for a couple of reasons. One is it eliminates the need for another thermostat, and will prevent the potential to run heat and AC at same time. The other reason is for units that have heat pumps. I originally thought that the box in the AC control just provided a set of dry contacts to control the furnace, but now thinking it's a little more. I have Dometic's and on mine if you turn the furnace on and it doesn't light for some reason, it will attempt 2 restrikes; if it still doesn't light after the 3 attempts it will default and turn the heat pump on. To do this operation there has to be come communication with the furnace other than a start signal.

[Ron C]

B. C.

I guess that’s why it is encouraged to stay with the same brand devices. The electronic controls would all work seamlessly with each other.

My unit, being a 2011, might not have as complex a control box. I will try keeping the old control box in the ceiling removing only the 120V feed and the output to the old topside AC and see what happens. Failing that, I’ll have to re-wire a way to control the furnace.

Thanks
Ron C

[prndl]

Ron,
I have the same model and year Montana as you. It would be simple to route new thermostat wires from the furnace to the thermostat. The new heat pump can use the old 120V wiring. Ignore the controller.
If you still have the old original thermostat you can remove it and install a cheap heat only one from HD.
I'm going to install a new Furrion Chill Cube whenever they are available and that is what I am going to do. It has a remote control as well.

[Ron C]

prndl

You might be right. It does seem like the most simple, direct way to go, if it doesn’t interfere with the existing 12V feed to the furnace.

I’ve received delivery of the RecPro unit here at my home address. When I travel with it back to the Montana in a week for the install, I will be prepared with a single thermostat and explore what I can make best work.

I’ll let you know how the finished job went.

Thanks for your input,

R

[Ron C]

New AC/Heat Pump installed and running well!

Was able to remove from the control box the 120V feed and output to the old AC roof top unit. I then checked the function of my DuaTherm thermostat on furnace mode. It still worked great. So I made a space in the front wall of the AC ceiling opening to hide away the old control box and wiring.

The opening was air sealed, the new RecPro installed and all is working fine, with the furnace on the old wall thermostat and the RecPro on remote control.

Thought I’d let you know in case anyone else faces the same problem.

Thanks for your input! All the best

Ron C