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Old 07-24-2012, 08:10 PM   #1
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Normal -> IP Thermostat Wiring

Hi guys,

I'd like to replace my standard thermostat with a Filtrete 3M-50 and have a question about wiring.

My current thermostat (that was originally installed with the house) has the following wiring..

RC - red
RH - red
W - white
G - green
Y - black

I have heating and A/C - which was installed sometime later.

As per the 3M-50's manual, I need a C-wire for non-batteried power to for the unit/wifi...

I keep seeing that RC and RH are just power and in some cases jumpered.

Can I simply use the wire from one of them for C on both the HVAC and thermostat side and jumper RC and RH on the thermostat side? or can I simply draw power for C from RC or RH?

.. or does it seem that my HVAC unit needs RH and RC seperately and it'd be best for me to run a new C separately? are there any kind of gauge requirements or can I cannibalize an accessible Cat5e cable to run the C over?


Last edited by duren; 07-24-2012 at 08:16 PM. Reason: More detail
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Old 07-24-2012, 08:35 PM   #2
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RC and RH are for independant transformers. They would have a transformer in heating system and transformer in the cooling system. this is typical with hot water heating and forced air cooling but not always. You can't use one as you C terminal. If it works the way it is wire it the same on the new tstat and use batteries.


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Old 07-24-2012, 08:41 PM   #3
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I see now you need a commom or c for wifi. you will need to connect a wire from the common side of your transformer to the tstat. the real question is do you actually have two transformers and if you do which one to use for the common. I would think you would use the one tied to RC but just a guess
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