Heat pump thermostat

Defect or no defect?

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Not sure I know what you may think is or is not a defect.
Thermostat is not programmable.
Set to heat, fan auto, inside temp 70, requested 68… inside temp is higher than requested so heat should be off.

I must be missing something so obvious its scary but I’m not sure what you are looking at.(been a long day and brain is tired)

Some small houses use a condensor outside and the heat strips in the airhandler are the only heat source, in that case all the t-stat needs is what you see in the picture.

Also, in some areas you find many heat pumps without the electric strip package installed so the t-stat can be what you see.

The heat strips are considered an accessory by the manufacturer but I think they are needed to prevent very cold air during the defrost cycle. They also are nice to have when the outside unit gets covered up during an ice storm or the temp drops into the single digits.

Is this a two stage stat? Does the heat pump have an ambient low temp lock out? Would not call it a defect based on the pic.

Is this an appropriate thermostat for a heat pump with heat strips? Would a heat pump in SC without heat strips be appropriate, where winter temperatures below 30 are frequent and they may go as low as 15 degrees?

No, but you have to confirm that it really is a heat pump, many systems use electric strips for the only heat source and that is connected to the regular heat mode switch as shown.

Would a heat pump in SC without heat strips be appropriate, where winter temperatures below 30 are frequent and they may go as low as 15 degrees?

**It depends on whether or not the unit uses R410, these systems are much better. I always educate my client, in the summary, about the four purposes of having these strips installed.

Eliminate some of the chill in defrost mode.
Heat source if ice storm covers the unit in ice.
Heat source if compressor quits running.
Additional heat if very cold outside or you need to raise the temperature several degrees quickly.**

I have on rare occasions found where a standard electric furnace was replaced with a heat pump system for all the obvious reasons but during the course of replacing it, the thermostat was not replaced with one for a Heat pump. I see no evidence of any way to select / test Emergency Heat on the thermostat in the photo. I have also seen just the opposite situation; a heat pump thermostat on a standard electric furnace. We see similar discrepancies regarding the breakers for HVAC equipment; the old system used a 50 amp breaker whereas the new system uses a max of 25 amp but no one changes it cause, well, it works and for the time being that is all they care about. Over the years I have seen just about any kind of bastardized way to install something anyone can dream up. This is why we all have a job.

Thermostat lacks an emergency heat setting to allow the heat strips to engage without the use of the outside compressor.

possible scenario based on the above…

“Matt, you inspected my house last month and I had a guy come out and install a heat pump t-stat as you said I needed, ($150) the emerg heat still does not work so I had a guy come out and he said there were no strips in there as you reported, it cost me another $250 for the strips and the labor for installation. Please send me a check for $250 asap, and I have an electrician coming to verify the branch circuit size can handle the new heat strips so that could be another $400 if that is also needed, thanks.”


If it was an inspection I would identify if the unit had electric heat stips or not by amp probing the conductor inside the panel. If the electric heat strips did not engage I would report the following:

[FONT=Times New Roman][size=3] The system is a heat pump without the normal electric heat strips that provide a source of auxiliary and emergency heat. The thermostat lacks an emergency heat setting to allow the heat strips to engage without the use of the outside compressor. Heat pumps require auxiliary (heat strips) to provide adequate heat when ambient temperatures reach 40 degrees and below. If the heat strips are present, they did not engage in the “Heat” setting and the system should be further evalauated to determine what repairs are needed.

We have a lot of heat pumps in Fl. If I see a reversing valve and confirm it’s a heat pump, I check the unit while it’s in heat pump mode, ensure cool air is blowing from the unit and that the suction line is warm. Once the thermostat is cranked up, the electric heat strips engage. I amp probe them to see how many Kilowatts the strips are and get the rating. Then I turn it to the emergency heat setting and make sure the outside unit turns off, then I check my amp probe again to make sure the strips are still on. There are some thermostats that do not have an emergency heat setting and you have to hit the mode buttom and up arrow at the same time.[/size][/FONT]

After reading the entire thread,

It would not be a thermostat defect if heat strips are Not present, however the unit should have auxiliary heat stips and I would identify that the units lacks electric heat strips. If the the compressor failed then home would not have a heat source and if the outside temps were below 40 degrees the heat pump may not be aduquate to heat the home.

That’s when the EH setting and electric heat strips would come in handy.


Sounds like you have a good process for inspecting heat pumps. Many inspectors do not realize the extra effort these take as compared to gas furnaces. We have many in crawlspaces so its not feasible to do the exact same process as yours. I ike to run the eheat mode first while the air in the ducts is cool so that its easier to notice the strips running.

One thing though, I would not state that heat pumps may not be adequate when temps are less than 40. It all depends on how old the unit is, these newer R410 units are awesome. I have two of them that were new in 2001 and they will work fine in the low 20’s. I have measured 105 degree air with the electric strips off on a low load day (low 40’s). I have my strips programmed to stay off unless very cold outside, they still come on as needed during the defrost cycle.

You have to wonder how many heatpumps out there don’t work correctly but are still being operated with only the electric strips for heat. I have never found a client or homeowner who really understood the modes and lights on the heat pump t-stat other than clients who are hvac techs or engineer types.

The unit in question was definitely a heat pump. Heil unit. New construction.

This house was about 2600 SF, 2 stories. Not a “small house”.

After inspection over 1000 homes in NC and SC, about 40% of them heat pumps, I think I’ve found maybe 2 without heat strips. That’s a defect in my view. I’ve confirmed the need for heat strips in our geographic area with a local HVAC contractor.

A necessary accessory.

Joe, its good to see that we both agree, as usual.

I suppose it is area specific. My house has a heat pump, and no electric heat strips, and that is somewhat common for this area.

If you’re certain it’s a heat pump, and it has heat pumps, it needs a “heat pump” thermostat.

Any of you using an amp clamp to make sure that the heat strips are working? I can’t tell you how many times I’ve found one not working.:wink:

I use an infrared thermometer at the register. I note the temp. using the fan only for about 15 minutes then turn on the emergency heat. That’s a simple way to do it.

What do you consider an acceptable temp? How does that tell you if all three strips are working, or only two of three? Not critiquing, just asking. :wink:

If the temperature doesn’t increase from the fan-only temp, it’s a safe assumption that the strips are not working. They usually heat the air to to upper 80s or even into the 100s after no more than 15 minutes or so.

Here’s one yesterday that it’s pretty safe to say the heat strips were not working.

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I agree. I’ve found 15 kw units with only 10kw working though by simply seeing if all three are drawing the appropriate amperage. The thermometer would tell me that I had heat, but not that it was working properly. I’m just sayin…:smiley: