Residential HVAC (Heat Pump) question

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MopaR&D

MopaR&D

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So it's that time of year here in Georgia where I'm sometimes using heat, A/C or having the windows open. My house has a heat pump and I noticed that when I use it in heating mode, the compressor only runs for about 5-10 seconds then kicks off and I get little to no heat from the vent registers inside. I did go out and touch the larger refrigerant line and it does get hot after it runs in that mode but still hardly any heat inside the house. If I just leave it like that it seems like eventually the electric "emergency" heater kicks on although I haven't gone in the air handler to actually check. Another weird thing is if I then switch it to A/C mode even if it's been sitting off for a long time (several hours) the compressor won't kick on. I went out to the circuit breaker and switched it off and back on, still didn't work then I turned the thermostat off then back to Cool and the compressor finally kicked on after about 5 minutes. Anyone know what could be going on before I call someone out to look at it? Or is this normal operation? This is my first time living in a place with this type of system, back in Colorado they typically used an A/C unit with a gas furnace for central heating. This is a Lennox system that was installed in 2019.
 
If there is a difference of more than a few degrees between the inside temp and the temp you set the thermostat to in heat mode, it will kick the emergency strips on to catch up quicker. When it gets to the point where the outside unit can handle it, the strips should kick off and the outside unit start and do the rest. I'm about 180 miles NW of you, so we get much the same weather this time of year. My heat pump is a Carrier and works like I described above. Cut yours on heat, let the strips do their thing and then see if it doesn't just switch back to heat instead of auxiliary or emergency heat. You for sure don't want to be GA Power's new best friend by letting the strips run forever! If they don't kick off and the outside unit take over before the house gets up to your set temp, then call someone to come check it. Clean your filter good too. My niece was bitchin about her AC not working, so I went to see if I could figure it out. Her filter looked like Chewbacca crawled in there and died! I replaced the filter and it took off running. Good luck to you.
 
That 5 minute "delay" is normal. It is a safety feature to prevent compressor "short cycling", while adjusting the t-stat or in the event of a minor power interruption.
 
JDMopar said:
If there is a difference of more than a few degrees between the inside temp and the temp you set the thermostat to in heat mode, it will kick the emergency strips on to catch up quicker. When it gets to the point where the outside unit can handle it, the strips should kick off and the outside unit start and do the rest. I'm about 180 miles NW of you, so we get much the same weather this time of year. My heat pump is a Carrier and works like I described above. Cut yours on heat, let the strips do their thing and then see if it doesn't just switch back to heat instead of auxiliary or emergency heat. You for sure don't want to be GA Power's new best friend by letting the strips run forever! If they don't kick off and the outside unit take over before the house gets up to your set temp, then call someone to come check it. Clean your filter good too. My niece was bitchin about her AC not working, so I went to see if I could figure it out. Her filter looked like Chewbacca crawled in there and died! I replaced the filter and it took off running. Good luck to you.
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Gotcha, so the air coming out of my vents shouldn't be very warm with the heat pump running, it's mostly just to maintain temperature... makes sense.

@Charrlie_S I am due to change the air filter since it's about 3-4 months old but the air flow is still pretty decent. I'll try to do that here soon.
 
I did some more poking around as it seems my heat pump still isn't working right. I took the panel off the outdoor unit and saw that one of the LEDs was lit up; it was indicating the system was in "high pressure lockout". I found an installation manual online which said that if the high pressure switch is triggered 5 times within one thermostat setting cycle, the system will shut down and go into high pressure lockout; this is why I've only been able to get it working again if I disconnect the power at the circuit breaker and turn it back on. It works fine in cooling mode but if I try to run it in heat mode the compressor will only run for 5-10 seconds then shut off. Searching some more online, it might be the thermal expansion valve but I think at this point I probably need to call a technician to come out and service it. Damn.
 
Could be a number of things or a combination of things. You already can tell the service technician more than most homeowners. Just as a dummy check, make sure you have a clean filter at the air handler. Refrigerant pressures are a function of airflow across the coils, ambient temps, condition of the refrigerant line components, and level of available refrigerant. Filter is probably not the issue, but its a cheap fix and the tech will hit you up for it ($$$) if it needs replacement.

To build on what JDMopar said, heat pumps usually produce air cooler than your body temp, so they won't feel hot like conditioned air produced by a gas furnace or your electric heat strips. Although some modern high efficiency heat pumps are cranking over 100F...
 
Set the indoor fan to constant operation and try running it in heat mode again. If it trips on HP again, you'll need a set of gauges. And likely a technician.
 
MopaR&D said:
I did some more poking around as it seems my heat pump still isn't working right. I took the panel off the outdoor unit and saw that one of the LEDs was lit up; it was indicating the system was in "high pressure lockout". I found an installation manual online which said that if the high pressure switch is triggered 5 times within one thermostat setting cycle, the system will shut down and go into high pressure lockout; this is why I've only been able to get it working again if I disconnect the power at the circuit breaker and turn it back on. It works fine in cooling mode but if I try to run it in heat mode the compressor will only run for 5-10 seconds then shut off. Searching some more online, it might be the thermal expansion valve but I think at this point I probably need to call a technician to come out and service it. Damn.
Click to expand...
Three things come to mind:

* Some Residential systems use a bi-directional filter/drier, and they can plug-up in only one direction.
* Bad reversing valve.
* Bad TXV (you've already mentioned this).

Regardless of the cause, most likely it's "internal", and you're going to need to call a Service Tech.
 
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One other thing: Don't hire a company that recommends cycling the power to reset the unit to clear the alarm. We call these guys "Disconnect Techs", and in general (and in my opinion), guys that do this need to stick to changing filters and washing coils.
 
ProjectBazza said:
One other thing: Don't hire a company that recommends cycling the power to reset the unit to clear the alarm. We call these guys "Disconnect Techs", and in general (and in my opinion), guys that do this need to stick to changing filters and washing coils.
Click to expand...

I'm going to call the company that installed the system since the previous owners of the house left that information here. They'd better be legit, I've already reset the unit a few times so I could get A/C back when we had some hotter days recently. I'm going to let them know I did a little bit of self-diagnosing, of course being careful not to make myself sound like a know-it-all because I've run into people like that back when I briefly had a job at a friend's parent's business servicing hot tubs and they're the worst.

I'm thinking I can rule out the reversing valve because the large line that normally gets cold during A/C operation does get hot when I run it in Heat mode. I just hope whatever the problem is it won't be too expensive to fix. The whole system is only 4 years old and that's obvious by the condition of all the components from what I can see. We're supposed to have our first freeze of the season tonight so I guess I'll set the thermostat fairly low and break out the space heater I brought with me from Colorado.

I did replace the air filter a few days ago, old one was clearly due for replacement but didn't seem to be causing much of a restriction. I ran the system in Heat mode again just now and same issue, 10-20 seconds of the compressor running then I could hear it start to struggle a bit and it kicked off.
 
MopaR&D said:
We're supposed to have our first freeze of the season tonight so I guess I'll set the thermostat fairly low and break out the space heater I brought with me from Colorado.
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If your tstat has an emergency heat or aux heat setting you can flip to it. That will engage the electric heat strips directly. You won't have to freeze, but it might lighten your wallet if you have to rely on it for a few days.

If the tstat is set up correctly, in normal heating mode, after a fixed period of time during which it does not see an increase in temp running heat pump, it will automatically engage the electric (or other backup) heat. It will keep backup heat engaged until it reaches setpoint, then let heat pump take over.
 
JDMopar said:
If there is a difference of more than a few degrees between the inside temp and the temp you set the thermostat to in heat mode, it will kick the emergency strips on to catch up quicker. When it gets to the point where the outside unit can handle it, the strips should kick off and the outside unit start and do the rest. I'm about 180 miles NW of you, so we get much the same weather this time of year. My heat pump is a Carrier and works like I described above. Cut yours on heat, let the strips do their thing and then see if it doesn't just switch back to heat instead of auxiliary or emergency heat. You for sure don't want to be GA Power's new best friend by letting the strips run forever! If they don't kick off and the outside unit take over before the house gets up to your set temp, then call someone to come check it. Clean your filter good too. My niece was bitchin about her AC not working, so I went to see if I could figure it out. Her filter looked like Chewbacca crawled in there and died! I replaced the filter and it took off running. Good luck to you.
Click to expand...
When a heat pump goes into heating mode it starts up the outside unit. If the outside unit can’t raise the temperature up a certain amount of degrees in a certain amount of time then it shuts off and the electric heating strips go on. My system is a little different. My backup heat is a gas furnace. It’s more expensive initially but my overall average utility bill is about $120 per month.
 
72Dinger said:
If your tstat has an emergency heat or aux heat setting you can flip to it. That will engage the electric heat strips directly. You won't have to freeze, but it might lighten your wallet if you have to rely on it for a few days.

If the tstat is set up correctly, in normal heating mode, after a fixed period of time during which it does not see an increase in temp running heat pump, it will automatically engage the electric (or other backup) heat. It will keep backup heat engaged until it reaches setpoint, then let heat pump take over.
Click to expand...

That's what I ended up doing last night. If I left it on normal heat mode it would run the blower for a long time waiting for the pump to kick on which obviously never happened then finally kicked on the emergency electric heater. I tried leaving it set to 67° but that was too cold for me to fall asleep so I bumped it to 68°. I turned it back to 66° this morning before leaving for work as I currently live alone, aside from my 2 cats. Tonight I'm going to set up my space heater in my bedroom and see if I can set the thermostat lower.

Probably a dumb question but is there any way to check or "unstick" the TXV from the outside? I can see it in the outdoor unit, ironically it looks brand new, same with the filter-drier...
 
Your best bet is let the tech look at it before you go any further.

The component you see through the top of the outdoor unit is the reversing valve. It is a slide valve and can get stuck in one position or the other. In some cases it can be tapped lightly to pop loose, but let the "pro" do that. (Edit: sometimes its not physically stuck...the solenoid could fail to trigger it for a couple of different electro-mechanical reasons).

The TXV is the component at the air handling unit that meters refrigerant into the coil. In heat mode it is bypassed outright.

You now know enough to be dangerous...
 
72Dinger said:
Your best bet is let the tech look at it before you go any further.

The component you see through the top of the outdoor unit is the reversing valve. It is a slide valve and can get stuck in one position or the other. In some cases it can be tapped lightly to pop loose, but let the "pro" do that. (Edit: sometimes its not physically stuck...the solenoid could fail to trigger it for a couple of different electro-mechanical reasons).

The TXV is the component at the air handling unit that meters refrigerant into the coil. In heat mode it is bypassed outright.

You now know enough to be dangerous...
Click to expand...
What he said.

Plus, and I'm speaking as a Commercial HVAC guy with almost 30 years of experience here:
toolmanmike said:
Call a tech
Click to expand...
Ditto (what he said).
 
I'm definitely not going to try anything on my own, I already figured it was a shot in the dark to ask that in the first place. I definitely know my limitations lol. LOVE that movie btw.
 
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