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Where to connect new C wire from Thermostat ..? Pic.

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  • Aug 2nd, 2015 12:15 am
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[OP]
Jr. Member
Apr 6, 2015
199 posts
141 upvotes
SW Ontario

Where to connect new C wire from Thermostat ..? Pic.

I am buying new Honeywell Wifi smart Thermostat to replace 17 year old thermostat which has 4 wires .
Instead of going diffrent options available to substitute with Gwire and stuff ,I can pull new wire .
On the circuit board in furnace - in the picture I have HRV and thermostat wiring on it .where will this new C wire go in the circuit board slot ?

[IMG]http://imagizer.imageshack.us/v2/280x20 ... VMM0cq.jpg[/IMG]
9 replies
[OP]
Jr. Member
Apr 6, 2015
199 posts
141 upvotes
SW Ontario
schade wrote: 24v COM
White wire from HRV unit is already in -putting a new one on top of it won't do any damage right ....?
Deal Addict
Mar 28, 2008
1639 posts
583 upvotes
ON
Mastero wrote: White wire from HRV unit is already in -putting a new one on top of it won't do any damage right ....?
That's your AC wire, and yes it's the COM along with the other white, but put it under the other side of the screw.
[OP]
Jr. Member
Apr 6, 2015
199 posts
141 upvotes
SW Ontario
sprdave wrote: That's your AC wire, and yes it's the COM along with the other white, but put it under the other side of the screw.
Instead of fishing new wire and messing with circuit board on furnace - can I take a wire from the one which is powering my HRV controller ,which in next to my thermostat ..? Tx
Deal Addict
Mar 28, 2008
1639 posts
583 upvotes
ON
Mastero wrote: Instead of fishing new wire and messing with circuit board on furnace - can I take a wire from the one which is powering my HRV controller ,which in next to my thermostat ..? Tx
Umm where does the cable from the HRV controller go to? Doesn't necessarily have a spare wire either, and really shouldn't mix the two systems anyway...

edit: as in where is the HRV unit in comparison to the furnace
[OP]
Jr. Member
Apr 6, 2015
199 posts
141 upvotes
SW Ontario
Ok so I have all the hardware now for running a new line - HD guy gave 14 gauge single wire instead of 18/2,3 to run from 24 v com to thermostat C point . Would 14 G be a issue here ..? Tx
Deal Addict
Dec 17, 2007
2619 posts
1594 upvotes
Alliston, ON
14g would be fine, although overkill. If you're running a new wire, i'd pull a 18/2 or 18/4 wire in. Down the road if you ever wanted to add another device and needed more wires to your thermostat, your all set.
[OP]
Jr. Member
Apr 6, 2015
199 posts
141 upvotes
SW Ontario
Cannot fish the wire - struggled for couple of hours too tight .Given Up
Back to option 2 as per Honeywell take out G green wire and put in 24 com and then put a jumper between G and Y .thus loosing manual fan .question is my y terminal already has red and blue wire on it - should I put jumper on it too -won't it be putting more load on it ?
Finally any suggestion on other better thermostat with 4 wires without all this . Tx
[IMG]http://imagizer.imageshack.us/v2/150x10 ... KT9j2K.jpg[/IMG]
Deal Addict
Jan 6, 2015
2860 posts
783 upvotes
Toronto, ON
Buy the Ecobee 3 and you won't have this problem. I didn't have a c wire and the Ecobee came with a lot to get power to the thermostat

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