Heat pump runs non stop when temps hit below 35 degrees?

[Hobby_Man22]

It held at 32 degrees last night for about 3hrs before warming up. The temperature held steday at about 2 degrees away from the target temp. I turned it up a degree and the heat strips kicked on and it warmed up another degree. So why do they design them to run non stop in cold temperatures? I guess down in the south most types of heaters pretty much run non stop at that temp any ways. My question is does the heat pump do something to keep the temp at a steady number? I lowered the thermostat a few degrees and it held steady for like 30 minutes before the heat pump kicked back on.

 

[930dreamer]

I think it goes into emergency heat and its full furnace and not heat pump.

 

[Certified Drunk]

Check the settings in the thermostat, most of them are set at 35*. anything below that should switch the furnace for heating.

 

[Hobby_Man22]

I think it goes into emergency heat and its full furnace and not heat pump.

It was 32 outside and it stayed on heat pump mode. The auxiarially heat only came on for a short period of time when I turned the thermostat up from 74 to 75

 

[Hobby_Man22]

Check the settings in the thermostat, most of them are set at 35*. anything below that should switch the furnace for heating.

There is no furnace.

 

[nadogail]

Looks like the OP needs a source of Auxiliary Heat.

 

[Yankeefarmer]

“They” don’t design heat pumps to run constantly at cold temperatures. But it’s a law of nature that at cold temperatures a heat pump will produce less heat than it does at warmer temperatures. The performance of your system will be governed by how your thermostat is programmed to use the aux heat strips.

 

[gmcgeo]

you may need some secondary heat to help when it gets that cold.

 

[Yankeefarmer]

There is also a difference in heating capabilities between different units of the same rated capacity. Below is a comparison between a Goodman two stage and a MRCOOL Universal that I compiled from claimed performance specs last fall.

 

[jack stand]

It held at 32 degrees last night for about 3hrs before warming up. The temperature held steday at about 2 degrees away from the target temp. I turned it up a degree and the heat strips kicked on and it warmed up another degree. So why do they design them to run non stop in cold temperatures? I guess down in the south most types of heaters pretty much run non stop at that temp any ways. My question is does the heat pump do something to keep the temp at a steady number? I lowered the thermostat a few degrees and it held steady for like 30 minutes before the heat pump kicked back on.

A heat pump is basically a reverse air conditioner, at least in theory. There's simply less heat available in your 32* temps and it switched to the "strips" that is simply electric resistance heat (think electric stove top).
There's newer technology in heat pumps and they can operate down to around 0* degrees using less electricity but depending on your electricity rates, most seems to have a 5* break point where it's cheaper to use your oil, propane or ng.
Your hp was running continuously because it was unable to extract enough heat to raise the temperature to the set point.

 

[gmcgeo]

Now, if it isn’t extremely cold out (above 35 degrees), and your heat pump does not reach the temperature set on your thermostat, this could indicate a problem. Here is a list of possible causes: items in blue need to be addressed and can be fixed by the homeowners – items in red require a licensed professional like those here at LHT!

I must not being seeing colors today

 

[theoldwizard1]

So why do they design them to run non stop in cold temperatures ?

Most heat pumps, especially central heat pumps are designed to only run down to about 40F. That is why they have heat strips.

The heat pump technology has greatly improved, especially for mini-split. If you live in a area where the temperature can get down below 40F, consider installing a secondary heat source, like a propane gas log.

 

[Yankeefarmer]

Most heat pumps, especially central heat pumps are designed to only run down to about 40F. That is why they have heat strips.

The heat pump technology has greatly improved, especially for mini-split. If you live in a area where the temperature can get down below 40F, consider installing a secondary heat source, like a propane gas log.

Or, you may be able to install a heat pump that is designed for cold weather heating. Below is a performance graph of my shop’s heat pump performance on a cold day last week. I don’t have any aux heat capability. I heat to 61 deg F when I’m going to be out there. A little bit before 11 am, I realized that I had to attend to some things in the afternoon, so being the cheap YankeeFarmer that I am, I set the thermostat back to 55 deg for a few hours. Note that, once the shop got to set temperature, it was only running about 50% of the time.

 

[jack stand]

You're demonstrating a lot of technology for a yankee farmer
All of these types of threads point back to your insulation. Very difficult to improve meaningfully in an existing house, but if you're building...
I don't remember how it was phrased, but somewhere I read something that "stuck" in my mind like; "the greater your insulation concerns, the less your heat source concerns and type matters".

 

[Big Dad]

I quit running my heat pump , electric bill went down $50 a month just run my furnace with propane .. works better

 

[American Locomotive]

I quit running my heat pump , electric bill went down $50 a month just run my furnace with propane .. works better

...yeah, and how much propane per month are you burning now?

 

[Big Dad]

...yeah, and how much propane per month are you burning now?

has not changed the amount of propane .. exactly the same

 

[brianh]

Most heat pumps, especially central heat pumps are designed to only run down to about 40F. That is why they have heat strips.

The heat pump technology has greatly improved, especially for mini-split. If you live in a area where the temperature can get down below 40F, consider installing a secondary heat source, like a propane gas log.

I just installed myself 2 Pioneer mini splits last fall it was 1 degree F twice this week heat output was the same, wattage did go up each one was pulling 800 watts while more normal for this area low 20's temps they average 500. I put kilowatt meters with real time wattage reading on their circuits just to track what I will use over the season. Our other primary heat is the wood stove. Per btu output the mini split is half the cost of what propane runs around here.

 

[Hobby_Man22]

Once it went from 32 to about 36 outside the heat pump caught up and shutoff. It must just be because the tempncoming out of the vents is cooler when it's cold.

 

[Hobby_Man22]

Do the heat strips come on without saying so on the thermostat? Mine says auxiarilly heat when the heat strips are on. I just wonder if they still come on temporarily without it saying so. I thought auxiarally heat kicks in when it goes into defrost but it didn't say so on the thermostat.

 

[u2slow]

Do the heat strips come on without saying so on the thermostat? Mine says auxiarilly heat when the heat strips are on. I just wonder if they still come on temporarily without it saying so. I thought auxiarally heat kicks in when it goes into defrost but it didn't say so on the thermostat.

My aux heat (when enabled) takes over when the heat pump can no longer make any gains.

Also consider the aux heat may be undersized. Mine was 4kW as installed (because it was only a 100A service), but it couldn't hold its own in the winter. I found a kit online to upgrade it to almost 10kW. (Its a York - parts were easy). Now it can keep up if we go away for Christmas.

 

[Hobby_Man22]

I think mine has 15kw its a 5 ton unit. Wish they would have went with 20kw. By itself the air coming out of the vent is like 70 degrees.

 

[niget2002]

When was the last time you had your system serviced? A heat pump works the opposite of the AC, but both rely on the refrigerant. I'm wondering of your system is low on refrigerant and keeping the heat pump from running optimally.

We had temps down into the 20's. At that point, my heat pump stops trying to heat the house and it uses the heat strips. We only have electric at this house, no ng/propane/etc.

Mine shows 'em heat' when it kicks on the heat strips.

 

[Showkey]

I think mine has 15kw its a 5 ton unit. Wish they would have went with 20kw. By itself the air coming out of the vent is like 70 degrees.

Thats why the unit runs nonstop and it’s also a common complaint with HP they never feel like warm air so they never feel comfortable.

 

[u2slow]

Mine digs into the aux heat below 8-10C. Its not an equipment problem.... It's the draftiness, and low R-value of 1973 construction. I'm sure I could tighten up the ductwork too if I spent the time.

I have a woodstove for real heat. Often run the air handler fan-only, for circulation.

 

[Hobby_Man22]

When was the last time you had your system serviced? A heat pump works the opposite of the AC, but both rely on the refrigerant. I'm wondering of your system is low on refrigerant and keeping the heat pump from running optimally.

We had temps down into the 20's. At that point, my heat pump stops trying to heat the house and it uses the heat strips. We only have electric at this house, no ng/propane/etc.

Mine shows 'em heat' when it kicks on the heat strips.

I have a feeling we were just barely at the threshold for aux heat since 32 degrees was as cold as it got.

 

[Jeepster04]

32F does seem a bit high for it to be running non stop. Lots of variables though.

I grew up with a heat pump and my parents still have a heat pump. Their house is insulated decent and their heat pumps will not run constantly at 32F. They will when it gets in the low 20's. When it gets in the teens, the AUX heat will kick on from time to time to warm up the house and it will cause the heat to quickly kick off. 10 or so minutes later, it will kick back on. Their AUX heat seems a bit oversized, when it kicks on, it gets hot in the house immediately.

 

[American Locomotive]

Not to beat this dead horse again, but do you still have the giant uninsulated metal garage doors on this building?

 

[Hobby_Man22]

Not to beat this dead horse again, but do you still have the giant uninsulated metal garage doors on this building?

I put radient barrier on them. It's way better than last winter. Last winter it needed the aux heat on the whole time when it was only 37 degrees

 

[justinjoyal]

Most heat pumps, especially central heat pumps are designed to only run down to about 40F. That is why they have heat strips.

The heat pump technology has greatly improved, especially for mini-split. If you live in a area where the temperature can get down below 40F, consider installing a secondary heat source, like a propane gas log.

40F was true a decade ago.

Entry-level heatpumps have been doing good down to 0F for years. The best ones put out a lot of heat even below -20F.

Of course, it doesnt produce full output and a properly sized heatpump(air conditionner) may not keep up during the coldest times of the year and that's why you need Aux heat.

 

[theoldwizard1]

40F was true a decade ago.

Entry-level heatpumps have been doing good down to 0F for years. The best ones put out a lot of heat even below -20F.

Maybe ! You live in Canada. He lives in TX. Probably not more than a dozen nights a year when the temp gets below 40F.

Buyer beware !! We don't know how old the OP's heat pump is.

 

[Hobby_Man22]

It's 1 year old and everything has been checked out on it. I do believe the installer say it was good to 40f. I guess next time around I'll get one good to 0. At the time I said it didn't get to 40 degrees very often where i'm at.

 

[Hobby_Man22]

Mine digs into the aux heat below 8-10C. Its not an equipment problem.... It's the draftiness, and low R-value of 1973 construction. I'm sure I could tighten up the ductwork too if I spent the time.

I have a woodstove for real heat. Often run the air handler fan-only, for circulation.

so yours goes into aux mode at a higher temp than mine. Draftiness isn't as bad as it seems. They make the new houses so air tight you can hardly breathe. The house I have now is from 1979 and when the wind blows hard enough you feel air movement in the house from it going through the windows. I hardy have any issues breathing and with allergies like I did in other newer houses

 

[danski0224]

It held at 32 degrees last night for about 3hrs before warming up. The temperature held steday at about 2 degrees away from the target temp. I turned it up a degree and the heat strips kicked on and it warmed up another degree. So why do they design them to run non stop in cold temperatures? I guess down in the south most types of heaters pretty much run non stop at that temp any ways. My question is does the heat pump do something to keep the temp at a steady number? I lowered the thermostat a few degrees and it held steady for like 30 minutes before the heat pump kicked back on.

Yes, there will be a point when the heat pump is on all of the time.

This is when properly sized ductwork and a variable speed blower are important.

There are two balance points, actual and economic.

Actual balance point is the coldest temperature where the equipment can meet the heating load.

The economic balance point factors in the load requirements (load calculation), heating performance of the equipment at a specific temperature (manufacturer spec) and utility costs.

All of that info will tell you the point where it is no longer practical to run the heat pump.

This balance point is programmed into the thermostat or dual fuel control.

The economic balance point needs to be re-evaluated when energy costs change.

Do not assume the economic balance point, it will cost you money.

 

[Gunfixr]

I have a heat pump here for the house, new unit replacing the old unit in early '17.
If the aux heat comes on, it shows on my thermostat.
The aux heat will come on if I bump the setting up 2 degrees or more, or if I bump it up at all while it's running. Bumping it back down, the aux goes back off.
Since, as mentioned, it's basically an air conditioner running in reverse, it's extracting heat from the outside air. From my observation, exactly how well this happens can be affected by humidity and wind, as well as the obvious outside temp. If it can get temp, but only barely, it will run longer. I think the short time between running depends on how quickly the building loses heat. So, at night, with no sun beating on it, or when windy, it runs more often.
When the unit was installed, I noticed the aux heat would come on around 24-27F, depending. During an inspection/tune up last year, I was offered a "compressor Booster", told it would ease compressor load, and increase the sere by half a point. Sere is how hvac efficiency is rated. This last winter, i've noticed a slight reduction in the electric bill, and the aux heat has not come on until down into the teens.

On really cold nights, I run the wood stove, which I installed while renovating, prior to moving here.
I'm in VA.

 

[FMB4]

It's 1 year old and everything has been checked out on it. I do believe the installer say it was good to 40f. I guess next time around I'll get one good to 0. At the time I said it didn't get to 40 degrees very often where i'm at.

There's your answer.

 

[FMB4]

Rented a large brand new 2bdrm apartment w/heat pump in '88. This HP did fine down to just below freezing (Bay Area CA). That said, as mentioned above, I'd run some type of auxiliary on the 'rare' occasions the your temps drop below 40 deg.

 

[u2slow]

so yours goes into aux mode at a higher temp than mine.

Yes - since the the 'heat pumping' ability has been exhausted at that point, it switches over to resistive heat.

A relatively 'tight' house is needed for an appropriately-sized heat pump to work effectively.

 

[PoorUB]

A heat pumps output drops as the temps get colder. It varies from manufacturer, but some will produce full output at 40 degrees, some will start to fall of at 0F. Either way, once you pass that point the HP produces less and less heat as the outdoor temps get colder.

Also proper refrigerant charge is important. If it isn't charged properly the performance suffers and you don't get the heating capacity you should. Plus the sad thing is most installers and service techs don't know, or will not use proper methods to measure the charge. As equipment has gotten more efficient it has gotten more critical to charge a heat pump or AC properly. Good old R22 was very forgiving and guys thet grew up on R22 think they can install R410 equipment the same way, but it doesn't work.

Also insulation and weather stripping matter and I know in your case we have beat this to death and it probably has not been addressed properly.

 

[Hobby_Man22]

I heat pumps output drops as the temps get colder. It varies from manufacturer, but some will produce full output at 40 degrees, some will start to fall of at 0F. Either way, once you pass that point the HP produces less and less heat as the outdoor temps get colder.

Also proper refrigerant charge is important. If it isn't charged properly the performance suffers and you don't get the heating capacity you should. Plus the sad thing is most installers and service techs don't know, or will not use proper methods to measure the charge. As equipment has gotten more efficient it has gotten more critical to charge a heat pump or AC properly. Good old R22 was very forgiving and guys thet grew up on R22 think they can install R410 equipment the same way, but it doesn't work.

Also insulation and weather stripping matter and I know in your case we have beat this to death and it probably has not been addressed properly.

Eh I'm happy with it. Holds at 72 degrees when its 32 outside. 40 degree difference. Not bad for just R30 rockwool insulation. No sheetrock, no Rmax foam board on the outside, no brick etc. An actual house has a lot more layers between the outside air and the inside.