Thread: heat pump thermostat

I saw a heat pump system today with no setting or indicator light on the thermostat for emergency heat. The system is less than two years old.
There is a 60 amp breaker in the panel labeled "heat". Access to the air handler in the attic is horrendous, but I also saw a 60 amp disconnect there.

Does it sound like the wrong thermostat was used, or what?

The outside temp today was about 75, and when I turned the thermostat up to 80 the outside unit kicked on and produced warm air. When I changed it over to AC it worked great. It's an electronic thermostat, so there are no dual mercury switches to look at.

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Since the heat strips are considered an option, if the option was not purchased then the basic t-stat would match the system operation.

The 60 amp circuit was put there "in case the buyer complains".

Its easy to add the strips and correct t-stat but the large circuit is much harder to do later.

I write up missing heat strips since they are used to knock the chill off during the defrost cycle and just a good idea for when the heat pump quits heating or it is really cold out.

Not too many heat pumps in PA I bet, but the newer ones will work fine up north.

Thanks Bruce.
Actually we have quite a few heat pumps around these parts. I just don't recall ever seeing one without an emergency heat setting or indicator.

If it was a newer digital thermostat you may have scroll through the choices to find the emergency heat setting. They are getting smarter and smarter it seems.

Thanks James.
It was a "newer digital" thermostat, but seemed to be a pretty basic one at the same time.
Even if you had to scroll through the menu to find an emergency heat setting, wouldn't there be an emergency heat indicator light to let you know that it was on?

Mine scrolls as follows:

Off
Heat
Cool
Auto
Em Heat

Fan
On
Auto

No lights indicate anything is on, though.

My 6yr Bryant/Carrier has a little > that points to either heat or cool if on.

If it has been manually put in emergency heat mode it displays "emerg" at the very bottom.

If it has automatically turned on the strips to "catch up" it indicates "aux heat" at the very bottom.

If it is in defrost mode no indicator shows up.

You can press the up and down arrows at the same time and get the outside temp and humidity level inside but this was an option and requires a temp sensor on the exterior unit.

If it is a heat pump stat, typically you should be able to scroll through the "mode" settings, cool, heat, aux. heat, off.
There are many different stat models out there now, but many do not have indicator lights now, just the notation on the display that the aux. heat is on.
Did you check temperature differential to see if the aux heat came on?

I have also seen this problem. There was a heat strip installed, but the thermostat did not show any indication of it. When the builder was asked about it, he indicated that the heat strip came on when the unit went into defrost mode. I didn't really believe that explanation. Most heat pump thermostats will automatically turn on the heat strip when demand is high, such as when the thermostat is turned up significantly higher than the interior temperature (some of them when demand is only 2 degrees higher). So, if I find a thermostat like you are talking about, I turn it up by 10 degrees and then put an ampmeter on the wires to the heat strip or the wires to the air handler in the electric panel. 5KW strip will pull about 22 amps - so at least I know it works. The air handler will only pull a couple of amps without the heat strip on.