Aux Heat coming on in mild weather (pt.2)

[ksm25]

I posted this on 10/18...

Hi Everyone,

I'm wondering why my new heat pump system is using the aux heat in such mild weather. I had a Carrier Performance Heat Pump installed in late July. (Outdoor unit is 25HPA524H0031010 and the Air Handler is FV4BNF002. New linesets were installed as well as a 15kw heat strip. The Thermostat is a Carrier TC-PHP01.) During the month of Aug. the A/C worked like a charm. This past week the temp. was in the low 60's so a switched over to heat for the 1st time. The thermostat was at 66 and I set it for 68. It seemed to be working fine but after 10 min it was only 67 (my sq. ft is only 1150) and at 15 min the Aux Heat came on and the fan Motor seemed to speed up a bit. My old system use to heat my home 2 degrees in 15 min with no aux heat. This does not seem normal when the temp outside is only in the low 60's. What is causing this ? I thought Aux heat was for very cold temps outside only. Thanks for any help...

I had my installer come back to check it out and he changed the changeover setting from the default 15min to 25min and said it was normal for the aux heat to come on. I still think something is wrong because last night it was in the low 50's outside and inside was 67 and I set for 68, after 25 min the aux heat came on and the fan kicked on to full blast which made it sound like a wind tunnell coming through the vents. This lasted for 4-6 min. This does not seem normal to me and certainly not efficient and it's not even that cold out (I live in the Boston area). It actually made my Bedroom (wish has 2 ceiling vents) to warm. Is this normal with the new systems? I am going to call the installer back, but want to know what I should be asking them to do. Thanks for your help...

[gary_g]

"Dash" is a Carrier guy.

His e-mail is in his profile.

Maybe he can help you.

At 50F ambient, your heat pump should put out a ballpark temp of 100F air after the indoor coil. Can you measure the temp after the coil?

[davefr]

Aux heat is often triggered to come on during a defrost cycle. Even in mild weather your condenser can automatically enter a defrost cycle.

Does the aux. heat turn back off after a couple minutes and does the sound return to "normal"?

[gary_g]

I still think something is wrong because last night it was in the low 50's outside and inside was 67 and I set for 68, after 25 min the aux heat came on and the fan kicked on to full blast which made it sound like a wind tunnell coming through the vents. This lasted for 4-6 min.

That does sound like the heat pump went through a defrost cycle. Next time it does this, check if the condenser fan (outdoor unit) is off. If off, it's probably in a defrost cycle.

[beenthere]

That does sound like the heat pump went through a defrost cycle. Next time it does this, check if the condenser fan (outdoor unit) is off. If off, it's probably in a defrost cycle.

Shouldn't be going into defrost when its 50°+ outside.

They should check/recheck the charge.

[Storman]

It sounds to me like the t-stat. A lot of the new t-stat have internal timers in them. This can be a bad thing when running a heat pump. Allowing the heat pump to bring up the temp inside is always better then brining on aux heat. I do not know about the T-stat that you have installed if it could be configured to look at the delta or distance away from set point to bring on the 2nd or 3rd stages of the system instead of the timer. I would also recommend to not use the setback program with a heat pump. Heat pumps are slow recovery and having a setback will a lot of times bring on AUX heat in the AHU.

[teaysvalley]

I have a new Performance HP/Hybrid system and my HP puts out very warm air at 50 degree outside temp. My set back at night is 68 and it ramps up to 73 for waking hours. My Performance HP has no problem getting back up to temp when in the 40s and 50s outside. You should give the HP more time than just 15 minutes to warm up 2 degrees. If your registers are not blowing warm air when it's 50s outside, something is wrong for sure.

My gas furnace is locked out above 35, so the HP is doing everything above that.

[platchford]

I had my installer come back to check it out and he changed the changeover setting from the default 15min to 25min and said it was normal for the aux heat to come on. I still think something is wrong because last night it was in the low 50's outside and inside was 67 and I set for 68, after 25 min the aux heat came on and the fan kicked on to full blast which made it sound like a wind tunnell coming through the vents.

If I understand you correctly, it did exactly what you said he programmed it to. After 25 mins the aux heat came on... which is what you said he changed the setting to. Personally, I prefer a thermostat with an aux heat lockout temperature setting. The other question I would have is if this is the same size unit as your old unit? That could explain why it takes longer to reach the temperature than your old unit.