8 votes

Can a Ground Wire be attatched to a nail in wood stud?

Install equipment in real junction boxes I've done a lot of wiring and I cannot imagine how you would get a ground wire anywhere near a 2x4. Your wires (including ground) are doing one of two things:...
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8 votes

How many wires should be in a new thermostat cable?

If you're building a new building and having new HVAC installed, I would simply put 1/2" conduit in the wall and be done. That way, you let the installer run the wire they need. I don't know that I ...
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7 votes
Accepted

HVAC Blower Fan stays on ALL THE TIME - Even when the system is off

A HVAC tech diagnosed and corrected the issue by replacing the electronics on the blower motor that had failed, as well as the blower. Thanks for all those who weighed in. I couldn't figure this out, ...
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  • 319
5 votes

Can I use the T terminal in my furnace as the C for a Wifi Thermostat?

Note: the solution here is the querent's -- I'm simply writing it up in a CW answer to get this off our plate as the querent has not returned to migrate it from his question-edits to an answer himself....
5 votes

How many wires can be connected to the C terminal at the furnace?

Technically, there should only be one wire connected to the screw terminal. However, it's common practice in the HVAC industry to connect more. If you want to do it the proper way, you should use a ...
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  • 128k
5 votes

Blue wire in Y: Thermostat wired right?

Does the heating and/or cooling system work correctly? Then it's wired right. "Correct" it at your peril. If it ain't broke, don't fix it. Do people often do things that are non-standard ...
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  • 134k
4 votes

Where do I connect my C wire from my thermostat when there are two transformers?

Okay... After reviewing your new photos, I think I have it figured out. This is what your system looks like You'll have to excuse the glitter pens, it's the only thing I could find on my wife's ...
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  • 128k
4 votes

How can I add a "C" wire to my thermostat?

The obvious answer is to run a new thermostat cable with five wires instead of trying to use jumpers etc that in the end just end up causing more troubles, like destroying a circuit board. In most ...
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  • 242
4 votes

How can I connect a WIFI thermostat to a Honeywell R845A switching relay?

According to this document, the internal wiring of that relay looks like this. It sounds like it's connected something like this. When the thermostat calls for heat, the T terminals are ...
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  • 128k
4 votes

How can I connect a WIFI thermostat to a Honeywell R845A switching relay?

I had the same problem with the same model switching relay and following the encouraging description given in a comment on Tester101's answer, made the same modification to expose a connection which ...
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4 votes

Can I buy a 24v transformer with a dedicated common c-wire feed?

Um, I don't know where you got the term "power stealing". What you describe as that, is exactly the normal way to do that thing, and the right way... unless you are aware of some capacity issue on ...
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4 votes
Accepted

How many wires should be in a new thermostat cable?

For traditional Heat + Fan + AC systems, you need 4 for the system to work at all, and 5 if you want to support the C wire for smart 'stats. However when you get into heat pump and multistage ...
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4 votes
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No C Wire Nest Thermostat

What you need to do is to move the Blue wire at the furnace over to the "C" terminal at the furnace. Then at the new thermostat connect the Blue wire to the thermostat's "C" terminal. Note that at ...
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3 votes

Installing of Honeywell Wi-Fi Programmable Thermostat

You'll have to connect the blue wire in the thermostat cable at both ends. Start by connecting the blue wire in the thermostat cable to the Comm terminal in the furnace. Then connect the blue wire ...
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  • 128k
3 votes
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Adding Venstar Add-a-wire to HVAC

You'll start by wiring the furnace and A/C as follows: Red from the furnace connects to Red from the thermostat cable and Red from the ADD-A-WIRE™ device. White from the furnace connects to White ...
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  • 128k
3 votes

Where is the C wire in this tangle of wires?

"C" is not always labelled as such. If you can determine the two wires on the 24V side of the transformer (load side), then find which of the two wires on that side is running to "R" on the ...
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3 votes

Added a new 5th wire for my wi-fi thermostat, now where to connect it?

You simply have to connect the new wire you ran between the "C" terminal on your thermostat and the "C" terminal on the furnace board. You can test with your multimeter, you'll get 24VAC between R ...
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3 votes
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Nest Thermostat Wiring for Baseboard Heaters

Since you have a R841C (with an integral transformer) You have your terminals on the relay confused. Connect RH to the HOT terminal from the relay and W1 to to the NEUTRAL terminal from the relay. C ...
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3 votes

Could I use this Speaker Wire for my thermostat?

Typical "thermostat wire" is a NEC/UL type CL2 cable, just like your speaker wire says it is, so as a replacement for an 18/2 thermostat cable, this will work just fine.
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3 votes

How to add C-wire from Laars mini-term

With only two wires between the thermostat and the boiler, you're not going to be able to power the thermostat, and call for heat. You'll need at least three wires for that. The C terminal on the ...
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3 votes
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How to add C wire to a very old 2-wire Lennox G16 Gas Furnace?

According to the wiring diagram for your system (i.e. Figure 2 in the linked PDF) -- the yellow wire on the 24VAC side is the C wire (it's the wire that goes to the compressor but not to the 'stat in ...
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3 votes
Accepted

Apart from a thermostat, where else can a C-Wire go?

Air conditioners need a C wire, too! That separate cable that is connected to your Y and C wires goes out to your air conditioner's outdoor unit. It connects to the coil of a contactor inside the ...
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3 votes
Accepted

Can I use a separate 24V transformer with an Ecobee 3 and an Aube relay?

This is A-OK Wire R and W from the relay box to Rh and W/W1 on the Ecobee, while leaving the relay's C terminal unused. Then wire the secondary of the separate transformer to Rc and C on the Ecobee. ...
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3 votes
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Isolation relay for Ecobee smart thermostat: NC or NO?

You're correct, you'll use the normally open (NO) terminal. When the thermostat calls for heat, it will energize the relay coil. The energized coil will close the contact in the relay between common (...
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  • 128k
3 votes

How do i hook up a new 5 wire cable to an existing 4 wire furnace

The thin blue wire at the thermostat is connected to the Y terminal, which means it is used to call for cool (air conditioning). You'll notice at the furnace, that the thin blue wire connects to the ...
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  • 128k
3 votes
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Home thermostat woes

Open the furnace so you see the control panel. Manually depress the kill-switch that powers down the system when the panel you took off is absent. Meter across the secondary terminals of the ...
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  • 46
3 votes

Adding C wire to WiFi thermostat

Look for the junction of brown wires and attach your C wire to that On the wiring diagram for your furnace, the brown wires are all C wires, and they come together at a junction that should be ...
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3 votes

Using a ground wire as a thermostat C

No way! A "return" is not the same thing as a "ground". In certain situations it is, but not here. The C wire (together with "the other half of the circuit") forms a ...
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3 votes
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C Wire to a Dual Zone House

If you have a spare wire at the stat then half the battle is done. Now you need to confirm it's viability at the source be it furnace, boiler, air handler etc. If the connected equipment is a furnace ...
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3 votes
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What Do I Lose With a Honeywell C-wire Adapter?

The "K" wire is a Honeywell-specific one that is used only with the Honeywell C-wire adapter and compatible Honeywell thermostats. The T9 is compatible. Everything will work the way it ...
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