# Re: Thermostat wiring help



## mriebese (Aug 12, 2016)

*Re: Thermostat wiring help*



Stedman said:


> Heres what the letters on your thermostat are:
> 
> o/b is for a reversing valve on a heat pump (you shouldn't use this one on your system)
> Y: Condensing unit control power (air conditioning)
> ...



Hi my HVAC thermostat only has 4 wires which I believe do the following
Blue - Cool
White - Heat
Green - Fan
Red - 24VAC

I would like to hook up a new Stat which has a Z-Wave network feature and I would like it to be always on with out using batteries.
I would be difficult to snake another wire back to the control board on the furnace. there is an electrical box right below the stat could I run a new wire from the stat common and tie it into the house white common?
Any danger in doing that? it would be much easier to connect in there. See pic of wires in the back of my old thermostat










Thanks for any help
Mike


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## mriebese (Aug 12, 2016)

*Re: Thermostat wiring help*

Just to answer this for others that are wondering. You can add a common so you don't have to use batteries if your thermostat wiring does not have a common. I have wall lighting switches right below so it was easy to snake a wire from the elec boxes' white common to the common on the thermostat.


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## WereBo (Apr 5, 2008)

*Re: Thermostat wiring help*

Hi mriebese and welcome to TSF :wave:

Apologies for no replies to your question, but wiring codes vary from country to country, plus a lot of folks have never used air-conditioning.

Meanwhile, many thanks for posting the fix for other members


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