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

[toyotadriver]

Stories like this is one of the several reasons I love my dual fuel heat pump/propane furnace. The heat pump heats the house well down to about 29* and then the outside thermostat tells it to shut off and it runs on the propane furnace. Heat pumps don't work great (or potentially at all) in extreme cold climates but in moderate climates, they work great. Nice warm air above 29*. But, when it's below 29* outside, my propane furnace heats the house with nice hot air. Plus, if we get a power outage, I can run my propane furnace off a small generator with no issues.

 

[Hobby_Man22]

The house has only heat strips. Doesn't matter how cold it is outside I still get hot air. Better than it feeling like the ac is on.

 

[Hobby_Man22]

I did have to turn the thermostat up a couple degrees so it would keep up. I'm not sure what's up with that. That's retarded. Then it gets hot when it does catch up

 

[Yankeefarmer]

Stories like this is one of the several reasons I love my dual fuel heat pump/propane furnace. The heat pump heats the house well down to about 29* and then the outside thermostat tells it to shut off and it runs on the propane furnace. Heat pumps don't work great (or potentially at all) in extreme cold climates but in moderate climates, they work great. Nice warm air above 29*. But, when it's below 29* outside, my propane furnace heats the house with nice hot air. Plus, if we get a power outage, I can run my propane furnace off a small generator with no issues.

When I was evaluating options for heating my new shop, I requested a quote for a dual fuel system from the local HVAC company I use. They wanted almost $15k to install a 3 ton HP/100k BTU propane furnace system, plus another $2k for propane tank if I wanted to own the tank. I had calculated my heating load to be 60 k BTU, so went with a cold weather capable 5 ton heat pump. My total spend buying and doing a self install was under $5k, no propane tanks or need to order fuel, and the system works when temps are in the single digits. (I haven’t found it’s limits yet, since in my 60 plus years living in this area the coldest I remember is -18, but we rarely go below -5. )

Now, if I were looking for a new system for my house, I probably would not have put all my trust in the heat pump only configuration. My shop system, though, has made a believer of me.

 

[fitter30]

Take a pick of the outside unit name tag. Temperature difference between filter rack and 18" " from evap coil with a pocket style thermometer running heat pump only.

 

[toyotadriver]

When I was evaluating options for heating my new shop, I requested a quote for a dual fuel system from the local HVAC company I use. They wanted almost $15k to install a 3 ton HP/100k BTU propane furnace system, plus another $2k for propane tank if I wanted to own the tank. I had calculated my heating load to be 60 k BTU, so went with a cold weather capable 5 ton heat pump. My total spend buying and doing a self install was under $5k, no propane tanks or need to order fuel, and the system works when temps are in the single digits. (I haven’t found it’s limits yet, since in my 60 plus years living in this area the coldest I remember is -18, but we rarely go below -5. )

Now, if I were looking for a new system for my house, I probably would not have put all my trust in the heat pump only configuration. My shop system, though, has made a believer of me.

6 years ago when we built our house, we paid $8000 for the entire system including duct work. Propane tank leased for $60 per year from the largest locally owned propane supplier in the area....who also has the best prices per gallon around. I can run my furnace with a 1800 watt inverter generator. I'm a believer. I've had an all electric house.....never again.

 

[Hobby_Man22]

Take a pick of the outside unit name tag. Temperature difference between filter rack and 18" " from evap coil with a pocket style thermometer running heat pump only.

They did that during the summer when it was 100 degrees outside. There was a 20 degree drop in temp 72 degrees going in and 52 coming out.

 

[Hobby_Man22]

I bought one of those fieldpiece probe pocket style thermometers after that. Thought they were neat. That's how I know if it's keeping up or not.

 

[firebirdparts]

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

Bigger ones cost more. The heat pump is putting in heat and the house is leaking it out. There is some break even point.

uestion 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.

The thermostat does something to keep the temperature at a steady number. You know that. It’s two stage heat, so If 2nd stage is required, the thermostat will turn it on at some offset like a degree and you’ll hover at that offset. Defrosting is the only complication to this system. Otherwise the heat pump is on when thermostat says be on.

 

[fitter30]

Bigger ones cost more. The heat pump is putting in heat and the house is leaking it out. There is some break even point.


The thermostat does something to keep the temperature at a steady number. You know that. It’s two stage heat, so If 2nd stage is required, the thermostat will turn it on at some offset like a degree and you’ll hover at that offset. Defrosting is the only complication to this system. Otherwise the heat pump is on when thermostat says be on.

Bigger ones cost more. The heat pump is putting in heat and the house is leaking it out. There is some break even point.


The thermostat does something to keep the temperature at a steady number. You know that. It’s two stage heat, so If 2nd stage is required, the thermostat will turn it on at some offset like a degree and you’ll hover at that offset. Defrosting is the only complication to this system. Otherwise the heat pump is on when thermostat says be on.

Thermostat is just a automatic switch for 99% of most furnaces and ac units. The only exception is very high seer rating units.

 

[PWC Repair]

Mine is an older, R22 heat pump. They run A LOT below 40 and do next to nothing (barely hold temp) when below freezing. The 410a units are better, the newer high seer variable speed inverter compressors are even better, able to put out heat down to around 0*. I don't like mine running a lot, seems like extra wear and tear on the compressor when it's not heating that great. What I did was install a dual fuel thermostat with an outdoor sensor. When it gets below 34* outside my heat pump stops and the strip heat comes on (which is staged). Puts out nice heat and cycles off. Problem solved!

 

[Hobby_Man22]

Mine is an older, R22 heat pump. They run A LOT below 40 and do next to nothing (barely hold temp) when below freezing. The 410a units are better, the newer high seer variable speed inverter compressors are even better, able to put out heat down to around 0*. I don't like mine running a lot, seems like extra wear and tear on the compressor when it's not heating that great. What I did was install a dual fuel thermostat with an outdoor sensor. When it gets below 34* outside my heat pump stops and the strip heat comes on (which is staged). Puts out nice heat and cycles off. Problem solved!

I have a 15kw heat strip on mine but it doesn't put out near the heat the heat pump does or even when they both run at the same time. That really kicks out the heat. I ran mine on emergency heat mode for a while because I thought the fan motor was out when it really just in defrost mode and that's when I found out the heat strips don't work well by themselves.

 

[u2slow]

I have a 15kw heat strip on mine but it doesn't put out near the heat the heat pump does or even when they both run at the same time. That really kicks out the heat. I ran mine on emergency heat mode for a while because I thought the fan motor was out when it really just in defrost mode and that's when I found out the heat strips don't work well by themselves.

Something doesn't sound like it's working properly... unless your house and air handler are huge - making 15kW "small" .

I know when my 10kW aux toaster kicks in because the air at the register gets hot like I'm used to from growing up with a gas furnace.

 

[Hobby_Man22]

It's a 5 ton unit.

 

[Hobby_Man22]

I think 20kw was the biggest heat strip you can put in it.

 

[u2slow]

Have you done a current-draw or continuity check? Part of it could be burnt out...

 

[Hobby_Man22]

It's brand new

 

[PWC Repair]

As stated, something's not right. When 15kw of heat is on, there should be TOASTY air coming out of your vents. My unit is 3 ton and only brings on 5kw at first.......unless the supply air is less than 90*, then 10kw turns on. Only with the 5kw going it puts out nice hot air.

Maybe a piece of ductwork has come undone or collapsed?

 

[Hobby_Man22]

As stated, something's not right. When 15kw of heat is on, there should be TOASTY air coming out of your vents. My unit is 3 ton and only brings on 5kw at first.......unless the supply air is less than 90*, then 10kw turns on. Only with the 5kw going it puts out nice hot air.

Maybe a piece of ductwork has come undone or collapsed?

They told me the emergency heat isn't going to heat as good as the heat pump by itself. That's all I have is 15k for the emergency heat or aux heat I guess you call it.

 

[justinjoyal]

Roughly:

5-ton equals to 60 000 BTU at 100% capacity. When it gets cold outside, that number drops.

15kw equals to 51200 BTU, constantly.

Let's say your system is moving 2000 CFM (400cfm times 5 tons), you should see a dT of around 24*F between supply and return air temperature near the air handler.

Your air handler should be pulling ~ 65 amps when running on AUX.

 

[u2slow]

As stated, something's not right. When 15kw of heat is on, there should be TOASTY air coming out of your vents. My unit is 3 ton and only brings on 5kw at first.......unless the supply air is less than 90*, then 10kw turns on. Only with the 5kw going it puts out nice hot air.

Good point about the aux heat being staged.

 

[Hobby_Man22]

Roughly:

5-ton equals to 60 000 BTU at 100% capacity. When it gets cold outside, that number drops.

15kw equals to 51200 BTU, constantly.

Let's say your system is moving 2000 CFM (400cfm times 5 tons), you should see a dT of around 24*F between supply and return air temperature near the air handler.

Your air handler should be pulling ~ 65 amps when running on AUX.

Oh it puts out atleast that much

 

[csp]

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.

Is this heat pump heating your home or a secondary building? Your posts are always so all over the place and ambiguous, it's hard to tell what the full picture is.

 

[Hobby_Man22]

Its a building

 

[csp]

And how big is the building? Ceiling height?

How many people reading and commenting thought this was your home I wonder.

Many made comments directly using the word house and you didn't correct them to clarify.

Another Hobby_Man22 train wreck of a thread.

 

[gmcgeo]

wait, you mentioned this is your house? this is separate building?

 

[Yankeefarmer]

And how big is the building? Ceiling height?

How many people reading and commenting thought this was your home I wonder.

Many made comments directly using the word house and you didn't correct them to clarify.

Another Hobby_Man22 train wreck of a thread.

Hobby Man did mention his house, but I never thought he was referring to his house when speaking about his heat pump’s performance. Don’t they teach critical reading skills in school any more? Or were you guys that were confused too busy smoking in the boy’s room when that was being taught?

 

[Hobby_Man22]

wait, you mentioned this is your house? this is separate building?

It's a red iron steel building like I've said many times before. Never once have I mentioned house or asked about my house.

 

[gmcgeo]

this must be where everyone got confused then

 

[Hobby_Man22]

this must be where everyone got confused then

Well i said it does pretty good with only r30 insulation all the way around. The steel building which is what I'm talking about only has that, nothing else. No brick, no rmax styrene panels on the outside etc. I did put put r30 on the walls mainly for better sound proofing.

 

[Hobby_Man22]

I don't understand why people keep commenting on thus thread. Being able to keep the building 45 degrees above outside temp is good enough for me.

 

[Hobby_Man22]

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.

Mine is designed for 40 degrees. Not sure why I didn't ask about a lower temp rated unit. I think they said a 5 ton unit rated at zero degrees needed 3 phase power. I may be wrong though because I also recall myself saying well it doesn't get down to 40 that often, but it's like every other year now we have a harsh winter.

 

[Hobby_Man22]

“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.

Aux heat kicks on and off but the entire system still runs non stop

 

[nadogail]

Unless I am completely confused; a heat pump is a reversible air conditioner. It pulls heat from one location and moves it to another, a Water Backed heat pump can refrigerate water and pull the heat out and transfer that heat into a building.

An Air Backed heat pump will find almost no heat in a below freezing environment.
If your heat pump is buried deep in something warm, it will work better.

If you had a decomposing pile of manure there will be a substantial amount of heat to be pumped into the space you want to heat.

 

[Yankeefarmer]

Unless I am completely confused; a heat pump is a reversible air conditioner. It pulls heat from one location and moves it to another, a Water Backed heat pump can refrigerate water and pull the heat out and transfer that heat into a building.

An Air Backed heat pump will find almost no heat in a below freezing environment.
If your heat pump is buried deep in something warm, it will work better.

If you had a decomposing pile of manure there will be a substantial amount of heat to be pumped into the space you want to heat.

Actually, there is heat available in air below the freezing temperature of water. My air source heat pump easily heats my shop when the air temperature is in the single digits without auxiliary heat, and it will even cycle off for short periods after reaching set temperature on cold days. It’s all a matter of properly insulating and sealing the building, and selecting a heat pump designed for cold climate conditions.

 

[PoorUB]

An Air Backed heat pump will find almost no heat in a below freezing environment.
If your heat pump is buried deep in something warm, it will work better.

They build mini splits that put out respectable heat at -20F, But I will agree that most residential units die off around 10F at the lowest.

It is not unusual with a HP and electric back up to keep the HP running. It will produce heat, but the reason we shut them off is the backup heat is generally more efficient. With electric back up the HP is probably running 1 to 1, or 100% so every dollar of electricity in gets you a dollar of heat, same as the electric coils.

Also in Texas they generally don't see minus zero weather so just keep the HP running and bump that back up heat to pick up the slack.

 

[Jeepster04]

My parents 4 ton trane (14 seer, its old) starts kicking the aux heat on when the outside temp is in the teens at night. The sun really helps heat their house, so if its sunny, their heat will kick off even if its in the 20's. The heat pump has no issues keeping the house at the target temp when the outdoor temp is in the 20's during the night. It cycles as expected in the 30's.

I do not think a properly sized heat pump in an insulated house should struggle at 32F.