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-   -   X wire on old thermostat (http://www.diychatroom.com/f17/x-wire-old-thermostat-19159/)

Jellybean 03-29-2008 12:14 AM

X wire on old thermostat
 
I have a heat pump with emergency heat function. Changing the old thermostat to a Rite Temp 8010. All the connections corresponded just like the installation manual said. Only question I had was the old thermostat had a black wire connected to an X terminal. The new thermostat, which has 2 AA batteries, said to tape off the X wire from the old thermostat. I did that and everything seems to work fine (didn't check AC today though). I also pulled the panel off the heat pump unit in the basement and the black wire in question above is connected to a C terminal (apparantly the common side of the 24 VAC transformer? I thought I read somewhere that I could go ahead and connect that black wire from C in the basement to C on the new thermostat and extend battery life? Or should I just quit while I'm ahead and leave well enough alone? Thanks.

biggles 03-29-2008 09:14 PM

if the new stat info calls for the C from the furnace hook it up for the comon sidde of the TR so you have a true 24V at the subbase.the newer stats with the larger LED screens and more digital options calls for a solid 24Vs the battery s to keep the stat info constant during a power failure until the power comes back up.

hvacdad211 03-29-2008 09:35 PM

you can hook up the wire to the c terminal on the tstat and then get rid of the batteries .

Jellybean 03-30-2008 08:14 AM

Thanks for your help. I appreciate it.


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