Old thermostat to new digital....please help! - http://www.hvacmechanic.com/ Forums
Original message
drbirch
"Old thermostat to new digital....please help!"
, posted Wed 16 Jul 19:44
I have an old Trane 239 thermostat for a heat pump system and would like to change it to a newly purchased Hunter thermostat model 44860. My old unit has the following wires/colors/my interpretation. Y (yellow)compressor W (white)auxillary heat G (green)fan R (red)power supply B (blue)heat mode O (orange)cool mode T (brown)temperature - not needed on new digital unit? X2 (white jumper from w) emergency heat
Here is my question. The digital Hunter unit has an existing jumper between Rh and Rc/R. Do I leave this jumper intact? Also, should I run a jumper from the "W" to the "E" on my new unit for emergency heat? Also - the new unit has a Y1 and a Y2 but my old unit only has a single "Y". Does it matter which one I plug it in to?
Any help is appreciated!
Replies:
Houston204
"Re(1):Old thermostat to new digital....please"
, posted Wed 16 Jul 20:28
Everything is correct except your B terminal. Trane's B is common. Hunter uses C for common.
When you set your stat cooling setpoint for 70 degrees, it will energize Y1 at 71 degrees. It will energize Y2 at 73 degrees. Use Y1.
Be sure to configure your stat for heatpump operation as described on pages 28 and 29.
Rh and RC = red C = blue Y1 = yellow W2 & E = white O = orange G = green tape off brown wire. Do not use the new B terminal.
Be sure to remove power to your air handler first.
"Old thermostat to new digital....please help!" 
