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#930617 - 01/12/18 05:46 PM Thermostat Change Out
FranS Offline
Carpal Tunnel

Registered: 01/21/02
Posts: 44822
Have an older Honeywell Thermostat and I just bought a new Honeywell Thermostat. Wires from the wall are Red, White, Green & Blue. Old thermostat hook up was: red to red, white to white, green to green and the blue wire went to a screw marked "C". New thermostat wants red to red, white to white, green to green, yellow to yellow and no "C" hookup. There is no yellow wire coming from the wall.

Three questions: What does "C" mean? Can I use the blue wire to the yellow screw instead? Will it screw up my HVAC unit, if I do that?

TIA
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�When the debate is lost, slander becomes the tool of the loser.� Socrates

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#930618 - 01/12/18 05:50 PM Re: Thermostat Change Out [Re: FranS]
CabinConnection Offline
Bigfoot
Carpal Tunnel

Registered: 01/20/04
Posts: 53067
Loc: The Indianhead's Left Nostril....
Honeywell model number for the new 'stat?

"C" = common

---> See also.

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#930619 - 01/12/18 06:09 PM Re: Thermostat Change Out [Re: FranS]
FranS Offline
Carpal Tunnel

Registered: 01/21/02
Posts: 44822
Series: RTH2300/RTH221

It is not wifi. Just standard basic tstat. I have no clue what the old ones model # is.
_________________________
�When the debate is lost, slander becomes the tool of the loser.� Socrates

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#930620 - 01/12/18 06:14 PM Re: Thermostat Change Out [Re: FranS]
CabinConnection Offline
Bigfoot
Carpal Tunnel

Registered: 01/20/04
Posts: 53067
Loc: The Indianhead's Left Nostril....
----> Does this help?

You may need to go to your furnace and identify where each wire goes.

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#930624 - 01/12/18 07:19 PM Re: Thermostat Change Out [Re: CabinConnection]
FranS Offline
Carpal Tunnel

Registered: 01/21/02
Posts: 44822
i have the manual (thanks), which is how I knew, in my first post, how they wanted the wires hooked up. I just don't know what to do about no yellow wire. frown


just found a youtube video and it shows my wiring in the wall and the tech said, blue is yellow. now, because my old had the blue hooked to the "C", maybe I should hook it up the same way. There is a reason that it was hooked up that way to begin with, right?


Edited by FranS (01/12/18 07:28 PM)
Edit Reason: Update
_________________________
�When the debate is lost, slander becomes the tool of the loser.� Socrates

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#930634 - 01/13/18 12:32 AM Re: Thermostat Change Out [Re: FranS]
RCovell Offline
Carpal Tunnel

Registered: 09/27/03
Posts: 6615
Loc: Jayhawk Land
When I've replaced t-stats, I ignore the color of the wire. What I'm interested in is what terminal are they attached to? The terminals are marked with a letter next to the screw terminal where the wire is.

Sometimes I get lucky and the letter corresponds to the wire color ie. B=blue, Y= yellow, etc. That makes it easy.

If not, I make a chart of wire color and terminal letter from the old t-stat. Then, the new t-stat instructions will tell you what terminal letter is where and you simply refer to your chart and connect the old wire that corresponds to that letter to the correct terminal.

Takes more time to explain that to do it.

Good luck, Bob.

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#930637 - 01/13/18 07:25 AM Re: Thermostat Change Out [Re: FranS]
AnthraciteSparky Offline
Handyman

Registered: 12/18/14
Posts: 755
Loc: Central Pennsylvania
Originally Posted By FranS
i have the manual (thanks), which is how I knew, in my first post, how they wanted the wires hooked up. I just don't know what to do about no yellow wire. frown


just found a youtube video and it shows my wiring in the wall and the tech said, blue is yellow. now, because my old had the blue hooked to the "C", maybe I should hook it up the same way. There is a reason that it was hooked up that way to begin with, right?


Just remember that some if not YouTube posters know less than you do.
_________________________
"Me, I'm just a lawnmower, you can tell me by the way I walk"

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#930673 - 01/13/18 02:52 PM Re: Thermostat Change Out [Re: AnthraciteSparky]
Clint_Robbins Offline

Carpal Tunnel

Registered: 09/19/01
Posts: 11313
Loc: Akron, OH
Quote:
Just remember that some, if not most, YouTube posters know less than you do.

Amen - and some correct YouTube advice is so common sense that it's unnecessary!

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#930848 - 01/15/18 07:18 PM Re: Thermostat Change Out [Re: FranS]
FranS Offline
Carpal Tunnel

Registered: 01/21/02
Posts: 44822
yep, not all youtube info is good. but this time it was. al also gave me a hint and further research has yielded some good info.

my old tstat did not use batteries, the "C" wire was used to keep power flowing to the tstats clock. new tstat uses batteeries, so i can use that blue wire for the missing yellow wire and go to the furnace and move the "C" wire to yellow and i should be good to go. i'll do that tomorrow and report back.
_________________________
�When the debate is lost, slander becomes the tool of the loser.� Socrates

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#930939 - 01/16/18 08:24 PM Re: Thermostat Change Out [Re: FranS]
FranS Offline
Carpal Tunnel

Registered: 01/21/02
Posts: 44822
well, got the wires done correctly on the tstat and at the furnace. however, i think when i originally did it wrong, i messed something up on the furnace. it won't come on. frown

have to call someone now. carpola!!
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�When the debate is lost, slander becomes the tool of the loser.� Socrates

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