[007noob]

Hi All,

I want to install a smart thermostat which requires a c-wire. My current York thermostat (Model S1-THEC11P5Y) does not have a c-wire.

I don't know where to begin with this one but... I am a little confused with the wires that are present at the thermostat as a different set of wires are connected at the furnace control board.
Please see the pictures below.

The bundle of wires (left of the transformer) are going go up to the thermostat. This bundle has an orange and black wire that are not being used.

To get a c-wire up to the thermostat could I take let's say the black wire and extend it to the c terminal on the furnace control board??? Would that be correct?

Just a couple of more notes:
1) On the furnace control board I tried to measure the voltage across the c terminal and each of the Y W R G terminals and got 0 Volts (even with the safety switch temporarily pressed on).

2) The present thermostat was install back in 2011 when the AC unit was replaced. They removed the humidifier unit at that time but left the Aprilaire dial thermostat and the wiring for it untouched.
So the rats nest of wires also includes this old Aprilaire thermostat that is no longer being used.

That's all I can think of right now to mention. Any help, clarification is welcome. Thanks!

 

[007noob]

Here is just another picture of the wiring at the furnace...

 

[joed]

The ecobee comes with a module to install at your furnace if you don't have a C wire.
The one time I installed one of these, it was straight forward if you follow the instructions that come with Ecobee.

 

[CaptTom]

Your furnace does have a "C" wire terminal.

I thought the only reason you'd need the extra transformer module is if you couldn't fish a wire from the furnace to the thermostat. You say you have two unused wires, so that problem is solved.

The next question is, which one is "C"?

It looks like your transformer is labeled "R" and (maybe) "C". It's hard to tell. You should have 24VAC across those. Assuming the "R" matches your thermostat "R," then the other one would be "C." But there's no guarantee the installer looked at those labels. It would work just as well if they were swapped.

The "R" terminal on the thermostat should be at the same potential (0V) as one of those, and read 24VAC to the other. That "other" is your "C."

 

[007noob]

Hi
On the transformer I measured 29 vac across R and C.

For the c wire could I use the c terminal on transformer rather than extending to the furnace control board?

Thanks


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[beenthere]

Connect the thermostat common to the C/common of the board. That's where your A/Cs common is connected.

 

[CaptTom]

For the c wire could I use the c terminal on transformer rather than extending to the furnace control board?

Probably. But...

Connect the thermostat common to the C/common of the board. That's where your A/Cs common is connected.

This is a better option. Are you sure that's the thermostat which drives the board? Are you sure the installer even saw the transformer's terminal labels?

If both answers are yes (which you could confirm with a meter and some time) then sure, it'll work.

 

[joed]

The PEK comes with the ecobee. Why don't you just follow the directions for a no c wire install. It took me 15 minutes for the one I installed.

 

[007noob]

The PEK comes with the ecobee. Why don't you just follow the directions for a no c wire install. It took me 15 minutes for the one I installed.

Well the wires on the furnace control board don’t seem to be the same set of wires on going to the thermostat. I’ll have to carefully check what is what.

Can I use the PEK regardless of the wires matching up?


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[joed]

I would say disregard the colours and use wires based on the label of the terminal they are connect to R,Y,W,C,etc at each end.
Use the directions that come with the unit. They were quite easy to follow if I remember. It was a year ago when I did this install.

 

[beenthere]

Here is just another picture of the wiring at the furnace...
View attachment 581245

Post a Pic of what wires are connected to the wires that are connected to the board.

 

[BayouRunner]

If the two wires that are circled are going to the condenser then you can just hook the black wire to the white wire circled. Then you can test it by measuring for 24 volts at the thermostat wires measuring from r to the black wire you just hooked up. You would need the cover installed and make sure the wires aren’t touching before you applied power to test.

 

[007noob]

Ok so I checked the wires on the control board going to the thermostat according to the labels and they do matchup. This time I traced all the wires by hand going through the “rats nest”. It is confusing at first when looking at it the first time.

And yes the two wires you circled do go to the control board. The white is connect to the C terminal and the red is connected to the Y terminal. This is shown in one of the pictures in the first post.

Now it seems pretty straight forward and making sense too. I can just undo the wire cap on the white wire and connect the black from the thermostat bundle which will become the common for the thermostat.

Should I also be able to measure the voltage on the control board between R and C terminal to get 24 VAC?

Thanks!

If the two wires that are circled are going to the condenser then you can just hook the black wire to the white wire circled. Then you can test it by measuring for 24 volts at the thermostat wires measuring from r to the black wire you just hooked up. You would need the cover installed and make sure the wires aren’t touching before you applied power to test.

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[beenthere]

Yes, R to C should show 24 volts or slightly more.

 

[surferdude2]

I'd check the humidistat wiring to see if it could have the "C" leg available. That control is just a switch leg for the 24 vac circuit that controls the humidifier. It can be in either leg of the humidifier supply so if need be, rewire it so it is in the "C" leg and you'll have that leg upstairs for other uses.

 

[007noob]

I checked voltage across R and C - it reads about 29 VAC.
Is that an ok reading?


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[007noob]

The humidistat has a brown and blue wire attached to it. These two wires are from the same thermostat wire bundle but they are NOT being shared with the thermometer. (I will have to recheck that to be sure.)
Anyways the humidifier is no longer there for many years. However the wiring and controls were never removed. I’ll probably make another thread for that when I decided to at least remove humidistat knob.

I'd check the humidistat wiring to see if it could have the "C" leg available. That control is just a switch leg for the 24 vac circuit that controls the humidifier. It can be in either leg of the humidifier supply so if need be, rewire it so it is in the "C" leg and you'll have that leg upstairs for other uses.

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[surferdude2]

That sounds very promising that you will have a wire available to connect to the Common 24 vac to power the new stat. Cool deal, so long as the humidifier control is going to be vacated anyway.

 

[beenthere]

I checked voltage across R and C - it reads about 29 VAC.
Is that an ok reading?


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Yes, that is fine.


Don't use the humidistat's transformer's C . You could end up burning up both transformers, and your thermostat.

 

[joed]

Why are you set on not using the PEK unit that comes with the Ecobee for a no C wire setup?