[justplumducky]

I'm working on a mobile home A/C system, self-contained unit outdoors. Has a common thermostat for the A/C and the indoor propane furnace.

Old thermostat has 24v red wire to RH terminal (jumpered to RC terminal), white to W, yellow to Y. There is a blue wire that's not connected - not sure what it's for (G terminal maybe to energize fan relay and run blower in the ON position of the Auto/On switch).

I bought a new Honeywell RTH111 Digital, Non-programmable thermostat, but there's a statement in the install guide that says, "This thermostat cannot be used if your old thermostat had any two of the following wires: R, RC, RH, 4 and V." The old thermostat doesn't have a separate wire for RH, and a separate wire for RC (they are jumpered). It doesn't have the R, 4, or V terminals.

The terminals on new Honeywell are in two separate banks and look like this: O/B Y R .... G W .

O/B is, according to install guide, for Heat Pump, if there is no backup heat system.

Is this new Honeywell thermostat compatible with this system for both Heat and Cool?

 

[gregzoll]

First, go look at the air handler to see what wires hook up on the circuit board there. Then compare to the install guide for the thermostat. If you do not have the books http://yourhome.honeywell.com/home/...Results.aspx?searchkey=rth111#expand/collapse

 

[justplumducky]

Thx for your reply gregzoll,

There's no circuit board on the A/C unit or the old standing pilot furnace.

 

[gregzoll]

There has to be a place for the wires to connect from the thermostat to run the blower, and fire the furnace when the call for heat on the outdoor unit. Go out and look at the connections for the colors, then match to what the installer guide shows. These thermostats work for both conventional & Heat pump systems. The directions are pretty straightforward.

 

[beenthere]

There has to be a place for the wires to connect from the thermostat to run the blower, and fire the furnace when the call for heat on the outdoor unit. Go out and look at the connections for the colors, then match to what the installer guide shows. These thermostats work for both conventional & Heat pump systems. The directions are pretty straightforward.

He seems to have a gas furnace and a package A/C unit outside. No fan wire is needed on many of them, nor can they use one.

 

[justplumducky]

Thx guys for the responses.

The wires connected to the old thermostat worked fine. Red-RH (RH jumpered to RC), White-W, Yellow-Y, G-terminal was empty. Not concerned, right now, about (G) or the blue wire that wasn't connected anywhere.

The new Honeywell RTH111 install guide has a statement in it saying, "This thermostat cannot be used if your old thermostat had any two of the following wires: R, RC, RH, 4 and V."

Old stat didn't have individual WIRES attached to each of its terminals (RH, RC, W, Y, G), cause RH and RC were jumpered, so maybe I have no problem and this new stat (with terminals O/B, Y, R, G, W) will work fine with the existing wires?

...but if it's talking about the new stat not working if the old stat had any two of TERMINALS: R, RC, RH, 4 and V (with individual wires attached to those terminals), then apparently it won't work with the existing wires?

Thought maybe someone would recognize this thermostat and tell me if my brain is just going way overboard with wires vs. terminals issue, and if this new stat will work with the existing wires as detailed above in first paragraph.

It is, indeed, an old Miller A/C Package unit outside and old standing pilot propane gas furnace inside (one thermostat serving both), without circuit boards on either. For example, yellow wire (cooling) from thermostat connects directly to the 24v coil on the contactor of the A/C unit outside.

 

[justplumducky]

Ok, I called Honeywell and he told that statement is, indeed, talking about WIRES, and not terminals - said the RTH111 will work with my existing wires. So I read too much into that statement and made a big deal about something that was obvious to everyone else.:clap:

 

[beenthere]

Should have no problem using that thermostat, based on what wires you said you have on the old thermostat.

 

[justplumducky]

Ok beenthere, thx much!