Heat Pump cooled well but barely heated

The Cooling cycle produced a temperature difference of 16 degrees between the supply and return vents. The Heating cycle only produced a temperature of 72 degrees, which is odd. Yes, the condenser was running during the heating cycle, so it wasn’t an issue with the reversal mechanism. I’m just at a loss of how the A/C could be working efficiently and then the heating (reversed) cycle work so poorly. Any ideas?


Welcome back Andrew! Just curious where you are located and what was the outside temperature when you tested the system? Certain variables may come into factor here.

1 Like

Thanks for the quick replies.

I’m located in Orlando, Florida. Temperatures were in the high 60s- Low 70s today.

I tested the Heater first because it was too cool inside to safely test the A/C. I ran it for about 30 minutes before switching over to the electric Heating coils.They produced produced 85 degrees temperature.

I tested the temperature with my infrared camera.

I’ve never taken heating differentials. My general understanding is heating either works or it doesn’t, from an inspectors perspective.

Correct me if I’m wrong, someone:

With a heatpump, you get a glimpse at the performance of system from the AC differential. As far as the unit is concerned, it works the same in either mode… just in opposite directions. Only other thing I have to confirm is proper operation of reversing valve. If there is a difference in performance, doesn’t it have to be because of conditions external to the unit? Aka, things I’m not concerned with during an inspection?

With a gas or electric furnace - I can check out the color of the flame for proper burning and whatever visible wiring there may be, but I’m not opening it up to check out the elements or heat exchanger.

Am I neglecting any part of a good insoection by not taking heating differentials?


Hello Andrew,

Did you obtain a general measurement of the cooling supply temperature? Do you know how old the unit was? When you inspected the evap coil unit were you able to open the case or at least view the coil from the air handler section?

If there is a problem I would suspect possible air flow issues from a dirty evap coil. I see so many here where the coils either are not accessible (they hang them in attics by attaching to evap case access panel), pookied shut (as they should be for air loss) and the pookie looks real old, or when visible they’re so dang dirty it is a wonder either heat or cool works. Nobody seems to pay the extra to have their coils cleaned and inspected annually.

The back-up heat coils obviously would not be affected by a dirty evap coil.

As far as Heat pump differentials, I’ve seen heating differentials far exceed the differentials of cooling. We look for cooling differentials to be between 14 and 22 degrees. I’ve seen heating differentials from a HP be between 30 and 40 degrees. So that tells me there is a difference between the cycles more than just the reversing mechanism. I just don’t know what that difference is either.

The cooling supply temperature was 48 degrees and the return temperature was 64 degrees. The units were manufactured in 2011. The evaporation coils in the Air handler were not inspected. I may be limited in my understanding of that facet of HVAC – I just don’t see how the evap. coils would work in cooling but not work as well in the reverse process. (Our business recommends the units be regularly serviced (cleaned) by an HVAC technician.)

I’m just technically curious how this could occur to further my understanding.

That’s why I asked what the supply temp was on the cooling side. Just as an FYI I have never run into such low supply temps even in our cooler weather in North Texas not that it isn’t possible. Also I have a heat pump in the exterior temps you mentioned my system will typically discharge in the mid to upper 90 range on back-up heat strips which is more than enough to warm the house.

There are various other issues to consider that can cause the lower temperatures.

  • Did you take the cooling temp and heating temp readings from the same supply register? I frequently find imbalances as I measure every register for consistency. If they were different registers for the heat test that might be your cause.
  • Were the registers closest to or farthest from the unit? I’ve encountered what appeared to be air flow issues (restrictions, etc.) that have affected readings.
  • Was the heat reading taken from an open or closed register? This can cause differences as well by restricting flows.
  • When reading in the manner you did it is not reading the actual air temperature and instead most likely the materials around it that are being affected by it. It is not hard to encounter anomalies from that and that should be taken into consideration.
  • You did mention that it was “too cool inside” indicating the system and house may have been possibly near exterior temp. The short run time might not have been sufficient enough to bring ductwork to a typical run temp and might have been indicated also by the 85 Degree heat strip temps. I test heat by running until it actually stabilizes at a final temp but that sometimes does take more than 30 minutes.

There are many different issues that can cause the issues you describe and it could also be a drop in the unit’s efficiency due to exterior/interior conditions, age, etc. You can also encounter the one off odd deal that just might be normal for that particular system. Go back through not only your testing steps, locations, sequence, etc., but the home condition for items that might effect this (for example ductwork sealing issues) and you might be able to come up with a plausible reason.

1 Like

I think you are making the right decision. In Texas I believe differentials are required. From listening to the pro’s on here, doing anything other than using a probe to include a good understanding of the Delta T and differentials you are likely going to get yourself in hot water.

For the record, I make the same observations as you. I do not go further.

Along with a disclaimer that it is not accurate the way they approve it being measured and to contact TREC if they have questions about the disclaimer! :rofl:

1 Like

I am not in Texas, but that disclaimer makes me wish I was!

Was the heat reading taken from an open or closed register? This can cause differences as well by restricting flows.

I did notice the home had several closed registers, but I recorded cooling and heating temperatures from the register in the kitchen, which were close to the Air handler. 30 minutes running a heating cycle from the Heat pump should produce a better temperature differential than the Heating coils did that ran for 5 minutes, that produced much more heat.

In short, running the Heat Pump for heat-only for 30 minutes produced only 72 degrees of temperature and the electric coils produced 85 degrees in only 5 minutes, from the same register.

I always scan the temperature coming from the supplies all around the home. The reason I even switched to the emergency heat was that we were finishing our inspection period and the house was still too cool safely test for A/C efficiency. This heating test from the Heat Pump just had me boggled as to why the A/C worked well but the system in reverse cycle did not work as well.

With exterior temps in 60’s to low 70’s it is not really a very good indication of the systems current efficiency in the cooling cycle during your much warmer Summer months. I have a standard disclaimer about that situation when I test in lower temps like that here. It’s possible that the simplest explanation is that the unit is not performing as it should and the cooler exterior and interior temps only make the cooling side look good for a test. Since we can’t duplicate our hotter exterior temps (Florida and Texas) to see what the unit is actually capable of the only option at that point is to refer it out if we feel it is not functioning correctly.

There is nothing wrong with your approach and wanting to know. Unfortunately unless we go where we are not supposed to (into a licensed trade’s area) it becomes a bit frustrating not being able to be 100% complete for the client.

I understand that lower temperatures can interfere with gauging the efficiency of the A/C, however the heating was not up to par. That’s why I recommended further evaluation by a HVAC technician, who may know something we do not. And that’s all we can, safely, do. Thanks for all of your input.

1 Like

So we go in for the deep dive but end up in the shallow end anyway. This is why I make simple observations and simple recommendations. “In my opinion, the system was not adequately cooling at the time of inspection. Recommend further evaluation by a qualified HVAC contractor.”

No we just go into the deep conversation of various possibilities because Andrew wants to know more and there is nothing wrong with that. It is actually very good to use deep thought as it helps better understand what might be seen at the next problem home.

BTW Andrew was reporting low heating temps with cooling that appeared to be functioning properly on a heat pump unit.

It would also possibly affect the efficiency of the heating whatever the issue might have been. It is just the appearance the unit was functioning properly in cooling but only because of the low temps outside.

Yes, this was the initial question. I don’t think the efficiency of the cool A/C readings was affected/mixed by the temperature outside. The doors were closed. The home was well insulated, I will add, but that would not affect heat transfer.

Sorry, I did not make myself clear. We do the deep dives on here and in research. All necessary. But, I have come full circle as to what I can reasonably accomplish in the field. So, thru experience I have learned that unless I am going all in on temperature differentials during an inspection it is best to keep it simple.

And I see the conflict in his observation. Is there a slim possibility this is a cooling only unit (AC) with a heat-strip furnace?

The condenser does not have an apparent indication of being a heat pump in the model code or anywhere I can see on the manufacturer’s label. The only thing that makes sense is that the thermostat was made to accommodate a Heat and Em. Heat option. The heat I read on infrared during the heat pump cycle may have been the heat in the attic transferring to the ducts at noon, under sunlight.

I’m 99% certain you hit the nail on the head.