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Mechanical or electrical device used to control a heating, ventilation, and air conditioning (HVAC) system, or other temperature reliant system.

3 votes
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Thermostat Wire Terminals

The thermostat power delivered from the furnace nominally 24 VAC. If you shorted out the RED (R) and BLUE (B) connections at the thermostat you would end up shorting the 24 VAC supply in the furnace. … This would certainly render your thermostat non-operable and it would could: Blow a fuse in the furnace, Overheat the 24 VAC transformer in the furnace, Render the furnace control functions non-functioning …
Michael Karas's user avatar
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1 vote

Installing c wire in older furnace

Your furnace may very well not have a distinct connection point for the "C" wire to route off to the thermostat which is often the case in older furnace designs. …
Michael Karas's user avatar
  • 66.5k
3 votes

Connected C-Wire (previously unused) to thermostat, but still no power?

You may have done the very same thing at the thermostat end of the blue wire. …
Michael Karas's user avatar
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1 vote

how to add c wire to heat pump ac unit (only have wires with nuts)

You will have to remove that taped up wire bundle to ascertain if there is one wire in the cable from the thermostat that is not used. … If so then the it can be re-assigned to be the C function to the thermostat. At the furnace end that re-assigned wire will have to be connected in with the wires as highlighted in blue as above. …
Michael Karas's user avatar
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2 votes

Help connecting unused C wire for Smart Thermostat

Once you identify the wiring harness that attaches directly to the frame ground (or transformer connection #5) you can tie your spare wire in the thermostat cable into that harness wire. …
Michael Karas's user avatar
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4 votes
Accepted

No C Wire Nest Thermostat

Then at the new thermostat connect the Blue wire to the thermostat's "C" terminal. … It is not clear what the Yellow wire in the cable bundle from the thermostat connects to at the furnace end. There is a good chance that this is connected incorrectly or not at all. …
Michael Karas's user avatar
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1 vote
Accepted

Thermostat/Furnace Wiring Confirmation

From your picture it looks like in reality that the yellow (Y) wire from the fatter thermostat cable connects to the red (R) of the smaller two conductor cable. … The yellow (Y) wire from the thermostat is typically the conductor that is energized to call for cooling. …
Michael Karas's user avatar
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1 vote

Connecting thermostat common wire to air handler or boiler?

You will lose the 24VAC power feed to the thermostat if you do that. … Another thing you should check is if the thermostat will run with just one of the Rh and Rc wires connected. …
Michael Karas's user avatar
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3 votes

thermostat connections with different size wires

It would generally be unusual to find a low voltage thermostat connected up with a large sized wire unless it was a line voltage thermostat. … If there is any feasibility to replace the 14AWG wire used for a low voltage application like this with widely used multi conductor thermostat wire please do consider doing so. …
Michael Karas's user avatar
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1 vote
Accepted

Can I safely reconnect thermostat wire on furnace controller?

The W terminal for a thermostat connection (normally also mated with a white wire) is the one used to initiate a "heat call" from the thermostat. … This would have been done to prevent any surprises from the thermostat when service was in process. …
Michael Karas's user avatar
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2 votes

Can I add a slave to existing thermostat?

Placing a second parallel thermostat or moving the single thermostat to the colder room will not be an ideal solution for you. …
Michael Karas's user avatar
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1 vote

How to simply turn heating on/off with VRT 340f thermostat?

I reviewed the manual for your VRT 340f thermostat online. It does not appear that this unit is intended for use in a simple on/off on demand mode. … Your most logical choice may be to replace the thermostat with a different model that offers the simple level of control that you desire. …
Michael Karas's user avatar
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2 votes

electrical range - oven temperature not set

The oven control problem could be either the temperature sensor or the thermostat. … In the case of the thermostat the control mechanism may be broken in an number of ways depending upon the type of control that it is. …
Michael Karas's user avatar
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2 votes

How can i figure out which wires go where, if the colors at the furnace don't match the ther...

If the wires from the old thermostat to the furnace are not the same colors at each end it seems to imply that there is a cable splice somewhere along the run where someone did a hack job of the splice … Write down the color relationship for a permanent record and for use in aiding you in connecting up the new thermostat. …
Michael Karas's user avatar
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