Electric heat pump question

[jhc77]

More like a heat pump vs emergency heat cost thing. Various outlets say switch to the emergency heat when it dips below a certain temperature to keep the house warm or at a comfortable level. Our house is isn’t the best at retaining anything (on a crawl space) but the heat pump is keeping up. 
Switching over to Emergency heat will pump in hotter air then shut off like normal but curious to know if a constantly running heat pump fairs in electricity usage to an intermittent emergency heat usage.

 

[tacops]

Someone with more knowledge than I may give better, more accurate, info.  Many reasonably modern heat pumps will automatically switch to supplement with electric heat strips "emergency heat" if the temps drop below a certain point.   You can manually switch most thermostats to electric heat strip "emergency heat" if your compressor fails, or your heat pump just cannot keep you warm etc.  Just bear in mind that the heat strips cause your electric meter to spin like a gas pump dial during the Obama era.  When I had a heat pump I never really "felt" warm yet the house was ok.  I have had gas heat for the last 20 years and won't go back unless I am forced to.

[MacGyver]

Modern heat pumps operate better at low temperatures than older ones - but the fundamental problem remains - there's just not much heat to pump in from the outside if you will.  Somewhere in the 25-30F range is typically where running the heat pump isn't going to really be efficient anymore.

If your heat pump automatically switches over to auxiliary heat - it likely knows where that efficiency point  is and fires up auxiliary as needed.

[jhc77]

11 minutes ago, MacGyver said:

Modern heat pumps operate better at low temperatures than older ones - but the fundamental problem remains - there's just not much heat to pump in from the outside if you will.  Somewhere in the 25-30F range is typically where running the heat pump isn't going to really be efficient anymore.

If your heat pump automatically switches over to auxiliary heat - it likely knows where that efficiency point  is and fires up auxiliary as needed.

It does switch to auxiliary around these temps. My crazy mind thinks why can’t there be a recirculating type system on these things by now. Seems to be easier to reheat 65-70° then to make heat from 25° and lower. There might be just not residential type set ups. 

[gregintenn]

20 minutes ago, jhc77 said:

It does switch to auxiliary around these temps. My crazy mind thinks why can’t there be a recirculating type system on these things by now. Seems to be easier to reheat 65-70° then to make heat from 25° and lower. There might be just not residential type set ups. 

Google "geothermal heating and cooling".

[jhc77]

10 minutes ago, gregintenn said:

Google "geothermal heating and cooling".

I read up on this years ago. I’m talking closed loop heat pump set up. Or as closed as you can get. I can smell a skunk sometimes if it wanders by. This house is drafty. If things go as planned it’s being sold in a month or so. Just curious if it’s cost effective to let the heat pump run or let emergency heat cycle. Hopefully this mess will be gone by next week. 

[peejman]

21 minutes ago, jhc77 said:

I read up on this years ago. I’m talking closed loop heat pump set up. Or as closed as you can get. I can smell a skunk sometimes if it wanders by. This house is drafty. If things go as planned it’s being sold in a month or so. Just curious if it’s cost effective to let the heat pump run or let emergency heat cycle. Hopefully this mess will be gone by next week. 

Let the emergency heat cycle on its own.  Leaving the emergency on will wear out the bearings in your electric meter. 

Heat pumps are outside because they're noisy and you don't want the refrigerant in the house if it leaks. They do recirculate the interior air, but its trying to draw heat from the cold outside air. 

[jhc77]

57 minutes ago, peejman said:

Let the emergency heat cycle on its own.  Leaving the emergency on will wear out the bearings in your electric meter. 

Heat pumps are outside because they're noisy and you don't want the refrigerant in the house if it leaks. They do recirculate the interior air, but its trying to draw heat from the cold outside air. 

I’d leave it on Auto still. Trying to hold out on using it for sure.  So far we’re good on heat. 

[leroy]

jhc...

Just let the unit run on its on.  I know this sounds crazy, but a heat pump is nothin but a " switch hittin " air conditioner.  The condenser and evaporators change jobs depending on " cool " or " heat ".  They are efficient as anything down to about 25 degrees. 

Below there, they still work, just not as efficiently as gas furnaces n electric furnaces.  The problem with them is that the heated air feels cool. Dont worry, it aint.  The few degrees above the set temperature will keep the house warm.   They work very well, they just aint warm like a gas furnace or a fire place. 

When ya turn on the " Emergency Heat ", ya are simply addin a electric resistance heater to heat the air more than the heat pump circuit does. As others have said, resistance electric heat is very expensive...

stay warm... leroy...

PS... We are electric heat pump folks too...

 

[MacGyver]

My physics professor in college had an early heat pump.  He said when he saw that emergency heat light come on he knew he was going to be eating peanut butter and jelly. 

 

[papa61]

I'm not turning on emergency heat until the temp in the house starts dropping. as long as your unit is maintaining set temp let it be.

[Darrell]

I have a mini-split system which has no auxiliary heating elements at all, and is 100% efficient to 0 degrees F.  That probably doesn't help jhc77 much, but if you're considering replacing your old system, the new mini-splits work great and cost a lot less to run. They are more expensive up-front, though.

[No_0ne]

3 hours ago, jhc77 said:

I’m talking closed loop heat pump set up.

That's what a heat pump does, but it has to get the thermal energy from somewhere.  On "regular" cycle, it tries to pump heat from outside to inside the house, but not outside air.  On "auxiliary" or "emergency" heat it supplants the heat gathered from outside with heat generated from electric strip heaters.  As others pointed out, if it's a fairly modern system it will do this as efficiently as possible, with older systems you were better off just switching to the "emergency" setting when the temps were much below freezing.  Regardless, when it's this cold outside, you're going to burn a lot more electricity with a heat pump.  They are extremely efficient when temps are in the "normal" range of about 20-100 degrees, which is most of the time in Tennessee.  Unfortunately, their efficiency goes out the window when it's zero outside ...

[Erich]

If your system is cycling to defrost very frequently (it will switch on the strips to offset defrost, which is really turning the AC mode on) that will let you know how well your set up is doing and what makes the most sense for any real low temps. At the point its continually having to defrost, you may as well just keep emergency heat on since it will warm better than having that same usage offset by it blowing cold air thru the handler when it is defrosting (blow heat thru the outside coils).  No free lunch.

New systems are efficient enough to let them do their thing, but older ones may not be and the intergoogles one size fits doesnt beat making a call based on your specific observations of how its working.

[gregintenn]

I just leave mine on auto and let it do it’s thing. It’s been doing that for 18+ years. We’ve been comfortable, and I can’t really complain about the electric bills. I wouldn’t have anything else. (I grew up cutting firewood.)

[peejman]

My parents have a dual fuel heat pump. The emergency heat is propane, they have an in-ground tank. 

Another point to note, most HVAC units will benefit from switching the air handler to "on" rather than auto. The HVAC works by moving air through the house, but a lot of units "on" time isn't enough to fully circulate the air.  It can take several minutes for the unit to get the air moving, so short cycle times leave warm and cool spots in the house and the extra cycles increase wear on the system. 

You might think running the fan 24/7 will use more electricity, but our electric bill went down $40/mo in the summer due to more efficient operation.  You also get cleaner interior air.  Newer systems usually have 2 speed fans so the low speed runs all the time and it switches to high speed when heating or cooling. 

[hipower]

11 hours ago, jhc77 said:

More like a heat pump vs emergency heat cost thing. Various outlets say switch to the emergency heat when it dips below a certain temperature to keep the house warm or at a comfortable level. Our house is isn’t the best at retaining anything (on a crawl space) but the heat pump is keeping up. 
Switching over to Emergency heat will pump in hotter air then shut off like normal but curious to know if a constantly running heat pump fairs in electricity usage to an intermittent emergency heat usage.

 

Can't answer your questions, but I will recommend NOT using the emergency heat setting unless it is a real emergency. If it's like mine...It will double or more your electric bill for the time it is on.

Don't ask how I know this. It's really embarrassing. And I was very PO'ed over it. 

[hipower]

6 hours ago, Darrell said:

I have a mini-split system which has no auxiliary heating elements at all, and is 100% efficient to 0 degrees F.  That probably doesn't help jhc77 much, but if you're considering replacing your old system, the new mini-splits work great and cost a lot less to run. They are more expensive up-front, though.

If we stay in this house, that's what we will do in a new system is required.

Seem the best for us here.

[leroy]

hipower...

RE: " Emergency heat vs Heat Pump cost... When ya turn on the "Emergency Heat", ya have, in effect, turned on an electric furnace.  It will run continuously until the temp reaches the set point ya selected on the home thermostat, then it will turn off.   A heat pump is more efficient (... Read that " uses less electricity "..) than the electric furnace no matter the duration of the run. That is why that the heat pump is billed as bein more efficient. 

Said another way, a continuously running heat pump will not use as much electricity as a continuously  running " electric furnace ".   Another way ta look at is this... My 5 ton unit compressor runs on about a 25 to 30 amp load, heating or cooling.  The strip heater breaker is rated at 100 amps... Its been down toward zero a time or two here, and we have never used the emergency heat... Im thinkin our unit is about 10 years old.

Hope this helps a bit..

leroy

[papa61]

18 hours ago, papa61 said:

I'm not turning on emergency heat until the temp in the house starts dropping. as long as your unit is maintaining set temp let it be.

it's y'alls fault. Just talking about it and temp started dropping in the house about 9 pm. ran emergency heat untill around 8 this morning
 

[Erik88]

I have never lived in a home that had this emergency heat option. We're still house hunting at the moment and I've been wondering if gas heat is always preferred over electric? 

[gregintenn]

5 minutes ago, Erik88 said:

I have never lived in a home that had this emergency heat option. We're still house hunting at the moment and I've been wondering if gas heat is always preferred over electric? 

I'd probably be happy with natural gas heat as it blows much warmer air out of the vents, but I live out in the sticks where propane would be the only option. I'm out on the propane.

[Hozzie]

If I had my options if I was building I would choose (in order).

GeoThermal

Dual Fuel (NG)

New Heat Pump (18-20 SEER)

NG

There is something mental about feeling warm air come out, but I also have a heat pump and it has done fine.  The biggest thing now is to get one of the heat pump units that has a high SEER rating.  I put a 20 SEER in my old house when I had to replace it and it was very efficient.   My house now is small (1500sf), but newish (2016) and it has two heat pumps.  I give the people that buitd it some credit, even though it is small, they put in two units, one for downstairs and one for upstairs.  It makes a world of difference in even heating and cooling.

[gregintenn]

Don't buy the cheapest heat pump. Get the one with the highest SEER rating. You'll more than recover your extra investment with cheaper electric bills.

[papa61]

4 hours ago, Erik88 said:

I have never lived in a home that had this emergency heat option. We're still house hunting at the moment and I've been wondering if gas heat is always preferred over electric? 

If I had a choice it would be a gas split unit. Seems like gas heat is not as dry.