Thermostat from Manual to Digital - DIY Chatroom

trinamillersmit · 06-30-2009, 06:13 PM

I have a 1994 Mobile home that has a Coleman Evcon Presidental ac/heating unit. The thermostat is the same brand (manual). I would like to replace the manual thermostat with a digital Hunter "Just Right" Model 42995b Thermostat, if that is possible. The problem is how to hook it up. My system has 1 rocker button that you switch to heat when you want to use the heater and cool when you want to use the AC. It also has another rocker button for Auto and Continuous. My manual thermostat is only hooked up with two wires. A red one and a white one. There are other colored wires (blue, yellow, green and one other color that I can't remember) that are also present, but they are not hooked to the thermostat in any way, they are just folded down. How do you hook this to the digital thermostat which has a red wire that is folded like the loop in shoe string (one end is attached the Rh screw and the other is hooked to another letter screw that I can't remember). So what do you do with the red and white wire from my old thermostat. Do I use the other colored wires I mentioned earlier with the new digital thermostat or can I just hook it up with the red and white wire.

beenthere · 06-30-2009, 06:26 PM

You won't be usig that thrmostat with that system.
That system requires the thermostat to be both direct acting and reverse acting.

Digital thermostats are not configured that way.
You would need to rewire the furnace controls, and add a relay or 2.

trinamillersmit · 06-30-2009, 06:50 PM

Thanks Beenthere for the reply. Do you know if I can use another manual thermostat? I just think the thermostat is not working properly.

beenthere · 06-30-2009, 07:18 PM

Yes, you can use most any standard thermostat.

I say your digital won't work.

But, some battery operated ones will work.
If your model is battery operated, try it.
But make sure it works in both heat and cool befoe you dispose of your old thermostat.

trinamillersmit · 07-01-2009, 11:20 AM

Beenthere, thanks again for your post. I just saw it this morning. The digital one that I have is battery operated and like I said in my earlier post. It is not the programmable kind. So, you think it could possibly work. Any idea how you would start hooking it up though since mine only has two wires (I mean two wires that are actually hooked to my old manual thermostat). Like I said earlier, I think my old thermostat is not working properly. It won't shut off even when the room is at what I believe is the desired temperature. However, you can move it up to about 80 or so then it will turn off.

beenthere · 07-02-2009, 11:21 AM

Just hook up the RH and W.
To the same wires that were connected to your old stat.