Problems installing programmable thermostat

[jackikevin]

We have a Coleman Evcon Presidential furnace and a Riverbend a/c. Our current thermostat is a Coleman, not sure what specific model, it's a box though. We took off the thermostat to put the new one on, to our surprise, there are only 2 wires. Red and White. We purchased a Hunter programmable thermostat from Wal-Mart, after it was set up the way the directions read, we turned the breaker back on and the a/c ran non-stop. The fan would not shut off. It didn't do that with the old thermostat. We thought maybe because it has just 2 wires and it seems like all of the new thermostats need 4. We went to Home Depot and asked them which one of the thermostats they sell will work with the 2 wires. We explained our problem. The guy recommended a RiteTemp universal thermostat. We hooked it up following all the directions, same result as the other thermostat. Are we doomed to never have a digital, programmable thermostat? What are we doing wrong or what is missing? Some one please help!!!

[Robert]

Hi,

There are a few different t-stats that work with 2 wire systems, haven't tried a programmable digital on one though.


For ALL 2 wires, you hook up red to RH and have a jumper from RH to RC.

You hook white to W .

You set switches at furnace control box to AUTO and COOL for a/c.

AUTO and HEAT for heat.


T-stat IF it has switches is set to AUTO and HEAT at ALL times whether heat or a/c.


Set temp lever where you want it to stay.



IF you go 4-5 wire, you'll need to remove the 2 wire control box and install a 4 wire a/c control box.


For a programmable, you'll need a battery operated t-stat or a common wire ran from transformer to C at t-stat.


Hope this didn't lose you and helps explain it .



Take care and best wishes,
Robert

[jackikevin]

The thermostat that we bought doesn't have any wire jumpers, can i make a jumper from extra wire we have laying around?

[Robert]

Hi,

How many transformers does your furnace have ?

IF it is only one, your t-stat should have a jumper from RH to RC.


It would be best to install a 4 wire a/c control box to use a programmable digital t-stat.

Then, if not battery operated, run a wire from transformer common side to C on t-stat.



Thanks,
Robert

[jackikevin]

We got the thermostat installed. We have to leave it on heat on the thermostat and change the heat/cool setting on the furnace. It's a little hard to set the cool temp since the thermostat thinks it running heat, but we got it. Thanks so much, they should have this kind of stuff printed in the instruction manual. Once again, thanks!

[Robert]

Hi,

Yes, that's what I explained earlier on 2 wire set ups. Just set t-stat where you want temp to be and it works fine with the help of a t-stat reversing relay inside the 2 wire a/c control box.



Take care and best wishes,
Robert