Heat pump auxillairy heat strips

[beachbum64]

Great forum! I have noticed when the outside temp drops below 34 deg, the aux heat strips come on when the heat pump comes on. They stay on for the entire running time. Is this normal? Thanks

[bmathews]

They shouldn't come on until the unit can no longer keep up or it is in defrost.

[beachbum64]

Thank you for your reply. I'll have a tech come out.

[amd]

There's probably nothing wrong.

- The system could be going into defrost without you knowing it.

- Depending on how it's set up, there could be an outdoor temperature sensor which brings on the aux heat at a preset balance point

- The thermostat might be very sensitive (high aux heat CPH setting) and call for aux heat before the temperature drops more than 1 degree below the setpoint.

[dhvac]

if ita always at 34 then thats probably right
its probably set there because at that point heat pump wont keep up with it anyway
always good to have units checked out yearly anyway but i dont think you have a problem. but i am not there to see it so take it for what its worth

and please post back what the finding were

[beachbum64]

Thank you all for your replys. I will double check the temp at which the strips are activated and if I have a tech come out I will notify you of the results. May you all have a wonderful Christmas.

[beachbum64]

I contacted a tech recommended by several of my friends re the heat strip activation. He came out and indicated that the heat strips would come on automatically at 34 deg or lower and stay on until the system shut down and that nothing was wrong. He suggested that I not change any settings. However, an acquaintance of mine said that the heat strips on his unit don't come on near as often as mine, even when the temp is below 32 deg. I don't have the manual for my heat pump. It is a Frigidaire 2001, high efficiency model. I don't have any specs for it. I'm beginning to think I should have the settings adjusted to lock out the aux until the outside temp reaches 25 deg. Any ideas on this? Thanks

[Irishmist]

Yes. Listen to the tech and not your 'friends.'

[gary_g]

I do not have the capability of locking out the aux heating strips or having them come on at a certain temp. I guess I don't have the Pro thermostat.

My Honeywell 7500 stat will cycle the aux heat on and off if the heat pump can't keep up. I like that it cycles as it's cheaper that way.

I think it's a good idea for you to figure out what your balance point is by locking out the aux at a lower temperature. I would do this gradually and see how it goes. From 34, I would go to 32. If that's OK, then go to 30. I wouldn't jump right from 34 to 25 degrees. The ability of the heat pump to keep up in cold temps depends on several factors including outdoor temp, heat pump size, btu output rating, ductwork, home construction, insulation, etc.

Best to you.

[Airmechanical]

you may be wasting a (bunch) of electricity, my heat strips are locked out until it reaches 15 degrees outside!



.

[thorton]

you may be wasting a (bunch) of electricity, my heat strips are locked out until it reaches 15 degrees outside!



.I agree with your thinking, Airmechanical! Every person and every house is different. If a HO has a heat pump, I believe they should lock out their aux strips (not duel fuel) as low as possible and see exactly what there heat pump will do. Then adjust the aux accordingly. It only makes sense to use the heat pump this way.

thorton
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[marter]

I contacted a tech recommended by several of my friends re the heat strip activation. He came out and indicated that the heat strips would come on automatically at 34 deg or lower and stay on until the system shut down and that nothing was wrong. He suggested that I not change any settings. However, an acquaintance of mine said that the heat strips on his unit don't come on near as often as mine, even when the temp is below 32 deg. I don't have the manual for my heat pump. It is a Frigidaire 2001, high efficiency model. I don't have any specs for it. I'm beginning to think I should have the settings adjusted to lock out the aux until the outside temp reaches 25 deg. Any ideas on this? Thanks

below 35 degrees or so the heatpump will lose more and more of its efficiency.
While it cost more to run the Electric Heat, its still cheaper then to use electric heat strips then to keep the heatpump running and not doing any good

[gary_g]

below 35 degrees or so the heatpump will lose more and more of its efficiency.
While it cost more to run the Electric Heat, its still cheaper then to use electric heat strips then to keep the heatpump running and not doing any good

This statement is wrong. Electric resistance is never cheaper than a heat pump (except in arctic climates). The btus that the heat pump puts out drops as the temperature decreases, but so does the power consumption of the compressor.

At 15F, my heat pump has a COP (Coefficient of Performance) of 2.46. This means that 2.46 kw of heat are produced for every 1 kw of electricity consumed. It is basically 246% efficient at 15F.

Many people do not want their compressors running constantly because of wear and tear, but that's a different issue.

[jrbenny]

Horse poop. Let 'em run.

[emcoasthvacr]

HP's should have mulit-stage electric heat strips for auxillary heat below the balance point of the structure.

I"d personally like to see multi-stage natural gas (NG) incorporated as the auxillary fuel in HP's, but so far I don't see it happening -- a lot of customers complain of lower heat temp of HP's.

I see mostly AC & Gas Heat in north Atlanta suburbs, and HP's with electric auxillary in most other southeastern locations.

Typically HP's have COP's of 1.5 at zero degrees ambient, but the btu/hr output crashes around 45 degrees ambient, and the HP just can't cut it.

[thorton]

This statement is wrong. Electric resistance is never cheaper than a heat pump (except in arctic climates). The btus that the heat pump puts out drops as the temperature decreases, but so does the power consumption of the compressor.

At 15F, my heat pump has a COP (Coefficient of Performance) of 2.46. This means that 2.46 kw of heat are produced for every 1 kw of electricity consumed. It is basically 246% efficient at 15F.

Many people do not want their compressors running constantly because of wear and tear, but that's a different issue.Great point, Gary G!!! Heat pumps with aux heat strips, especially if they are staged heat strips should always run no matter what the outside temperature. I'm also concerned with heat pump compressor running constantly when I first had the heat pump installed. But I finally got it squared away in my mind that heat pumps are not like furnaces (because most are oversized) and need to run lots. This is why I keep the set point temperature on the low side during the day and set back only 2 degrees at night.

thorton
______________________
If common sense is so common how come so few of us have it!

[bigrob36]

you need to check out the carrier infinity duel fuel systems they will let you use gas as a aux heat they are comeing out with a new three stage gas furnace that will work good

[ebierley]

you need to check out the carrier infinity duel fuel systems they will let you use gas as a aux heat they are comeing out with a new three stage gas furnace that will work good

But with duel fuel it is an all or nothing proposition. You can't run the fossil fuel furnace with the heat pump due to the higher discharge temps boosting the Refrigerant pressures.

[regis101]

I new to HP's also. Some of my first info stated that run times may be very long as outside temps drop.

This is my third season. This month, the second stage has not been used on purpose. Maybe I'm a glutten for punishment but I'm looking forward to my PG&E bill.

The first year was terrible. Everytime one of us felt a chill, up went the
T-Stat to bring on the second stage. The highest bill was $400. No more of that. Trying a set it and forget it approach and ( Let 'em run )

[bigrob36]

we duel fuel our units all the time the heat pump will not run when u are in defrost or you get below your aux lock out temp to operate a duel fuel unit well cost you less than a regular heat pump

[emcoasthvacr]

As far as I know, this statement is true -- can anybody correct this statement?


But with duel fuel it is an all or nothing proposition. You can't run the fossil fuel furnace with the heat pump due to the higher discharge temps boosting the Refrigerant pressures.

[second opinion]

As far as I know, this statement is true -- can anybody correct this statement?

The only time the heatpump and the fossil fuel will run simultainiously is during the defrost cycle. That is not to say that they will not switch back and forth according to lock out temperatures.:)

[Black Adder]

Agreed, heat pump will almost always be more efficient than electric strip. Try letting the Tstat control when aux comes on. Lock out the outdoor probe and see how well that works. Aux should only come on when pump can no longer keep up to heat loss.

[Airmechanical]

we duel fuel our units all the time the heat pump will not run when u are in defrost or you get below your aux lock out temp to operate a duel fuel unit well cost you less than a regular heat pump



what?:rolleyes::(:eek::confused:



.

[primecooler]

I'd be curious to know the model equipment you have. If lock outs are set then lower them. The charge of the system could be off. I would hope you would have a staged electric heater if the setting is that high. Mine wouldn't turn on unless 1) time on stage 2 heat pump expires or 2) defrost or 3) I manually set the t stat for elec heat. I have limited expierence with Nordyne equipment, Do they use TXV's at the outdoor unit? Good Luck

[beenthere]

His system may have been sized to the A/C load, and need to bring the strips on a little sooner.

[ccryan2000]

I have a new Lennox dual fuel system run by an IAQ that works very well, but when in HP mode, the family can't stand the freezing cold air during defrost mode that sometimes lasts 3-5 minutes. It is especially bad when you are in the shower or getting out. Since I have such low KW rates (3.9 cents per KWH), I am interested in adding a 5KW strip to the system for defrost. Is it an option to add to a dual fuel system to kick in duing defrost only?

[Airmechanical]

I have a new Lennox dual fuel system run by an IAQ that works very well, but when in HP mode, the family can't stand the freezing cold air during defrost mode that sometimes lasts 3-5 minutes. It is especially bad when you are in the shower or getting out. Since I have such low KW rates (3.9 cents per KWH), I am interested in adding a 5KW strip to the system for defrost. Is it an option to add to a dual fuel system to kick in duing defrost only?

no need for a heat strip

your furnace (should) kick on during defrost if your system is wired properly!

and that (should) leave you with warm supply temps during defrost!

have a pro check out your system, and make sure they are experienced with dual fuel systems!



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