Heat Pumps and Electric Heating - Replacing thermostat from TH3210D to RTH7500

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pete09
05-04-09, 07:57 PM
Hi,
I'm trying to replace my old thermostat (TH3210D) with RTH7500 for my heat pump upstairs but I'm having some trouble.
My TH3210D connection is as follows:
White = E & AUX
Yellow = Y
Green = G
Orange = O
Red = R
Brown = B
Blue = C

Now, from reading the manual for the RTH7500, I can connect pretty much everything except for the Brown wire. Can anyone please help me.
Thank you,
Pete

pete09
05-06-09, 07:21 AM
I believe I solved my issue. I ended up examining the compressor and air handler to see if the brown wire was connected. It appears that it was only connected on the thermostat side. I'm not sure why it was done this way. Perhaps to confuse the consumer from installing a programmable thermostat? :)
Pete
Jarredsdad
05-08-09, 04:19 PM
The O terminal is energixed in cooling. The B terminal is energized in heating.

Probably a new helper hook up this stat and landed all the wires he had not knowing what he was actually doing.

On the other end the installed knew what he was doing and didn't need the B hooked up to anything.