Replace Condo's 2 wire mechanical thermostat with digital thermostat - DIY Chatroom

kat83 · 05-22-2008, 01:29 PM

I decided for efficiency sake I want to replace the old mechanical white rogers thermostat with a new Honeywell digital programmable one. The digital programmable thermostat I have bought contains connection points for Rh, Rc, W,Y, and G.

The problems that I've run into are:

1: The condo has shared central heating and cooling such that in the Summer (May-October) you can only get cool air (A/C) and in the Winter you can only get warm air.

2: There are only two black copper wires to the unit and again depending on the time of year it either does A/C or Heat. The mechanical thermostat took care of this problem by connecting both the W and Y wire to one single wire.

Should I just get copper wires to split the 2 wire's from the unit into 4 (so that Rc, Rh, W, Y are all connected ) ? Is this even possible or a good idea?

Thank you for your help.

jrclen · 05-22-2008, 01:33 PM

Great question. Post this in HVAC and one of the heating and air conditioning guys will jump in to help you I bet.

J. V. · 05-22-2008, 01:52 PM

If you have a connection diagram (the one that came with the thermostat) and some multi conductor cable, you should be able to figure it out. Turn off the power before attempting any work on the system.
If you can scan or take a picture of the diagram of the thermostat and the one on the AC unit, post it. We may be able to tell you how to connect.