Heat Pump in bitter cold conditions

[Larry Sue]

It's just above 0 F and my heat pump is working almost non-stop. Is it more economical to turn electric heat strips and leave the outside unit off? I'd appreciate any advice.

Thanks.

[Bubba]

In general, leave it run. One would need the electricity cost in your area, the balance point of your home and the specs on your heat pump to determine which is more cost effective to run and when. Its a heat pump and they run a lot in cold weather. If you dont like it, turn it off and turn the back up electric heat on. Then watch the electric meter spin off the wall. Bubba

[Joseph Meehan]

I would love to hear the theory behind that one.

[Joseph Meehan]

It will decide for you. When it can not provide enough total heat the resistance heat will kick in. I would assume, which is always a bad thing to do, any well designed system would shut down the heat pump part when the temperature was so low as to be come less than 100% efficient. Sorry I really don't know if they do or not. If not, they need better engineers.

[Bubba]

Theory? You dont know how to figure balance point of a home? If you would read between the lines you just might figure out that the poster is complaining that the heat pumps runs almost 24/7 and is wondering if it should be turned to "em ht" and skip the condensing unit operation of her system. With electric as your back up, its still more efficient to run the heat pump than to just turn it off and run on electric resistance, even down to 0 degrees. Look at the performance specs of the unit and you might be able to understand. Just so you know, I have a gas 2 stg var spd gas furnace with a 14 SEER heat pump, fossil fuel kit and H/W Vision Pro stat. I f*ck with it all the time and I know what Im talking about. Would you like to see my utility bills before and after my heat pump addition, Joseph? Theory? God Damn idiot. Bubba

[twfsa]

I have a two stage 16 seer and it does a great job till 16 degs and then it switches over to n/gas. This month in Nebraska, bitter cold, gas bill $84.00. I would suspect my electric to run about the same, as was the case last winter.Winter of 04 gas and elec bills never exceeded $168 combined.

Tom

[PrecisionMachinisT]

Look at the cop specs on just about any heat pump--IIRC they drop down to about 2 when the outside temps get into the tens and below......so, unless the unit is defrosting 50% of the time, it is still more economical to operate as compared to electric heat strips.

Your total heat output drops too, though--but under this condition, so does the electrical current drawn by the compressor.

What I do here is I use a water source heat pump unit as a auxillary to our main air source unit--it draws some well water during the occasional cold snap we get in our area.....but as it only operates as auxillary, there isnt a huge or constant demand on the well--and with the ~50 degree well water, it maintains full heat output at a cop just a tad above 3

And in the summer, I can change the water source over so that it cools the house at the same time its heating the swimming pool.

[PrecisionMachinisT]

Only if its a programmable ( smart ) thermostat will it will fire the aux heat strips automatically, otherwise this same terminal on the air handler will also ( usually ) be tied in with a signal from the heat pump condensor in order to activate the aux heat strips whenever the heat pump goes into a defrost cycle.

Some systems will also ( but not always, by any means ) have an outdoor thermostat (as an option ) that will lock out the heat pump altogether once the outdoor temp gets below some set point so that on a call for condensor startup the signal will be bypassed and will instead energize the aux heat strips .

It all depends on the unit and the installer and the decisions that were made by both when it was purchased and placed into service.

Doubtful anyone is likely to go through the tedium to determine which might be the actual case over the internet--especially when we dont even know if the OP owns a meter or knows how to read the schematics for the unit in question.

Suffice it to say if the unit runs constantly, letting it run is probly the most energy efficient thing to do, and then if the house still gets too cold, turn on the aux heat also--but do realize this will make for a rather largish utility bill.

[Joseph Meehan]

Very nice Bubba but how does the price of electricity get into the formula? After all that was the question.

[m Ransley]

Bubba does not know electricity prices , Bubba does not care, Bubba uses no electricity, just wood.

[Bubba]

Joe, Quite honestly, I think you are just stupid and like to argue. Bubba

[Bubba]

Exactly what your head is made of. Should I burn that? Bubba

[Larry Sue]

Thanks a lot! Great answers!

[Stormin Mormon]

I live in a part of the world where we burn gas, oil, propane. Heat pumps hardly ever seen.

Thus said, I'd have to guess your heat pump is doing darn near nothing at zero F, and it's probably relying about 99% on heat strips.

We have several heating guys on this group (I have 3 years experience as a heating installer). The guys can be counted on to flame me, which will help warm your house.

[Bubba]

Damn Stormy. Why blurt out such ridiculous shit like that? Go grab any heat pump and pull the freaking access door off of it. Now read the damn thing. Its called a "Performance Chart" and it tells you some silly little information about the unit like: THE PERFORMANCE of it! You'll be very suprised. Now, try something else. Go grab the door off of a 14 SEER heat pump or higher. Wow! Even better PERFORMANCE! Now go read damit. Learn something for once. Bubba

[Brigitte]

Keep in mind that Nebraska has the cheapest electric rates in the nation. :)

Just one of the many reasons to live here. :)

Brigitte

[geoman]

Just to clarify one thing here, not all outdoor stats are to lock out the heat pump. Some outdoor stats lock out the aux heaters until it gets cold enough outside, thus preventing them from coming on when someone thinks the thermostat is an accelerator like on a car. All installations are different. Good post Precision.

[geoman]

What are the rates there for a KW? Do you have demands as well?

Rich