wrote:
I recently purchased a new Trane two-stage furnace and air
conditioner. I still have the old, non-electronic, non-programmable
thermostat that I have had for years (with my previous single-stage
furnace). The HVAC contractor said that it would be wise (but not
required) to get a programmable thermostat. His company actually
sells/installs them, but he said that I could save a lot of money by
doing it myself.

As I've started looking into this, I'm a little confused about whether
to install a single-stage or two-stage thermostat. I understand that
if I get a single-stage thermostat, then the furnace will start up
with the first stage and go to full heat after 10-15 minutes. With a
two-stage thermostat, the thermostat apparently has control over the
starting and stopping of these stages. Is that right?

My existing thermostat has four wires coming into it. I assume that
I'd have to run more wire to use a two-stage thermostat. Is that
right?

Yes.

If running the wires is too much trouble then just go with a single
stage 'stat. You probably won't notice the difference in performance
anyway.

Since you only have four wires (probably R,G,W,Y) you don't have a
common wire (X or C) which is required for power on some electronic
thermostats. Therefore, you need to choose a battery powered 'stat.

I'd recommend the Honeywell Chronotherm or Vision Pro (NOT the HD retail
version) thermostats. Assuming you don't have a heat pump, these would
be the thermostats of choice.

http://www.honeywell-thermostat.com/...thermostat.htm
http://www.honeywell-thermostat.com/...thermostat.htm

I don't know anything about this reseller, so this isn't a
recommendation to buy from them.