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Old 03-20-2020, 10:32 AM   #1
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Replacing Heat Pump Thermostat


Hi all,

I am trying to replace a thermostat on a Carrier Heat Pump but I'm running into an issue. The current thermostat is wired as follows:

Orange Wire into O/W2* the asterisk indicates that this terminal is O on a heat pump on the thermostat

Red Wire into R terminal

Yellow Wire into Y/Y2 terminal

Green Wire into G terminal

Blue Wire into C terminal

White Wire and Brown Wire are twisted together and both running into W/W1 terminal

Black Wire is not connected to a terminal

Everything is pretty straight forward for wiring the new thermostat except for the twisted White and Brown wires into W/W1. I'm assuming that these are the wires for the AUX/Emergency Heat and should be going into the W2 and E terminals on the new thermostat, possibly with a jumper between the two(Hunter thermostat).

It almost looks like the thermostat wasn't designed for the Heat Pump and someone "made it work"? Trying to get some input before trying the wiring or throwing in the towel and calling a tech. Thanks!
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Old 03-20-2020, 11:22 AM   #2
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Re: Replacing Heat Pump Thermostat


Model number of old and new stat?

Normally, there's no jumper between O and W2.
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Old 03-20-2020, 11:38 AM   #3
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Re: Replacing Heat Pump Thermostat


The model number on the new stat is Hunter 44860.

To clarify the O and W2, it appears that the old Carrier stat, which I cannot locate a model number on, is designed to run either and an AC or HP unit. The terminal is labeled O/W2* on the terminal and printed on the circuit board is: "*0 for HP, W2 for AC". There is also a resistor labelled R19 on the circuit board and above it is printed "Cut R19 for AC" and this resistor is in intact so the wire in the O/W2* terminal should be O.
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Old 03-20-2020, 01:01 PM   #4
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Re: Replacing Heat Pump Thermostat


Model of the old stat?

I would not use a hunter unit especially on a heatpump - get a honeywell or emerson/white rogers.
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Old 03-20-2020, 01:23 PM   #5
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Re: Replacing Heat Pump Thermostat


Again, I cannot locate a model number for the old stat. It is a Carrier stat but I cannot even locate anything online that even looks like it.

I went ahead and tried to wire up the Hunter but it is not activating any function of the heat pump. The old stat is able to turn on the indoor fan and the emergency heat but is not activating the outdoor unit(compressor or fan) when in either heat or cool mode. I wanted to eliminate the stat as the issue by using this Hunter stat I had laying around that I used in a previous home to test it but it isn't working at all.
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Old 03-20-2020, 01:27 PM   #6
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Re: Replacing Heat Pump Thermostat


stats rarely go bad and you shouldn't go changing parts to troubleshoot.

if you're unfamiliar with electrical and don't know how to check with a meter, it's best to call someone out.

You can further mess up your system changing out a stat incorrectly. heatpumps are not as straight forward to deal with as conventional systems.
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Old 03-20-2020, 07:40 PM   #7
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Re: Replacing Heat Pump Thermostat


Please don’t start changing parts trying to chase an issue.
Troubleshoot the issue first with your meter.
Changing random parts without troubleshooting digs you a deeper, more confusing hole to get out of, when the unit still doesn’t work and now you’ve lost track on what was changed or how something was wired.
Heat pumps require specific thermostats to function properly. It sounds like the Hunter is the incorrect thermostat.
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Old 03-21-2020, 04:58 PM   #8
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Re: Replacing Heat Pump Thermostat


The Hunter in not a "pro level" thermostat but it can control a multistage heatpump. I suspect it isn't working because of the odd wiring to the existing system. Not sure why you have two wires going to W/W1.
Another concern is that the old carrier thermostat isn't switching on the outdoor condenser. You may have a problem there, too (eg low pressure cuttoff).
As above, I think it may be time to bit the bullet and pay someone to go over it.

Last edited by sktn77a; 03-21-2020 at 05:10 PM.
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Old 03-21-2020, 05:29 PM   #9
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Re: Replacing Heat Pump Thermostat


Quote:
Originally Posted by Felnus View Post

I went ahead and tried to wire up the Hunter
Any chance you didn't turn off the power to the HP before you started?
If nothing at all works you may have blown a fuse.
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