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Old 11-22-2008, 05:57 PM   #1
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Help with t-stat 2h/1c


Hello. I have a Carrier Heat Pump System (electric, I think it is 2H/1C) that uses a Honeywell T874G thermostat with a Q674L subbase. My currernt thermostat has the following 7 wires:
1-W2
2-G
3-E
4-R
5-C
6-Y
7-O

I am interested in upgrading to a wireless t-stat so I can control the temp from upstairs. The only problem is that there is no E terminal on the new t-stat. This is the manual for the receiver of the new t-stat http://www.xpedio.carrier.com/idc/gr...m-tstat-10.pdf
It is a wireless carrier. http://www.residential.carrier.com/p...wireless.shtml

Basically my question is what to do w/ the E wire from my system. Should I just tape it up and not use it? I have read some posts online that E is sometimes jumped to W2 but that doesn't make sense to me and they are separate terminals on my current t-stat. Please help. Thanks!!
Also, it is possible that the new t-stat is not correct for my system?

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Last edited by intensol; 11-22-2008 at 06:00 PM.
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Old 11-23-2008, 06:44 AM   #2
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Help with t-stat 2h/1c


Your new stat probably doesn't require an E teminal because its internal circuitry uses W2 for the emergency heat, when switched to it.

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Old 11-23-2008, 08:27 AM   #3
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Help with t-stat 2h/1c


[quote=intensol;188684]Hello. I have a Carrier Heat Pump System (electric, I think it is 2H/1C) that uses a Honeywell T874G thermostat with a Q674L subbase. My currernt thermostat has the following 7 wires:
1-W2
2-G
3-E
4-R
5-C
6-Y
7-O
__________________________________________________ _____________


W-1, is for your reversing valve. Some package system uses two wires to power the two sets of auxilliary heat. I set is used during defrost mode or temp is below 35F, and the other set is for emergency mode only. You can either connect this W2 and E wire together to W2 terminal of your replacement thermostat or leave the "E" disconnected and taped up. The only way to verify how this "E" wire is connected to your auxilliary heat system is to trace this wire all the way to your indoor unit (split system) or outdoor unit ( package system).

Use the "6- wire, 1st stage cooling, 2nd stage heat" heat pump wiring instruction from the instruction manual.
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Old 11-23-2008, 04:05 PM   #4
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Help with t-stat 2h/1c


Thanks for the info. My thought was that if I connected W2 and E together and that terminal went live that they would both go on even though I don't need emergency heat. I'm guessing it doesn't work that way?

I don't have access to the split system because one is in the attic and the other is on the roof of the condo so I can't determine where E runs to.

Also, by what I described would you say that I have a 2H/1C heat pump system? The W2 is the 2nd heat cycle right?

Thanks again.
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Old 11-23-2008, 04:08 PM   #5
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Help with t-stat 2h/1c


Quote:
Originally Posted by intensol View Post
Thanks for the info. My thought was that if I connected W2 and E together and that terminal went live that they would both go on even though I don't need emergency heat. I'm guessing it doesn't work that way?

I don't have access to the split system because one is in the attic and the other is on the roof of the condo so I can't determine where E runs to.

Also, by what I described would you say that I have a 2H/1C heat pump system? The W2 is the 2nd heat cycle right?

Thanks again.
Your second stage is your electric heat or it could be Natural Gas in a Heat Pump.
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Old 11-23-2008, 04:09 PM   #6
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Help with t-stat 2h/1c


The W2 is the aux/seonf stage heat.
Your indoor unit uses the same electric heater for aux heat as it does for emergency heat.

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