9 replies to this topic

[az_repair_gal]

This one has us going crazy. The heat pump blows cold air before the sun comes up. Later in the day when the sun is shining on the roof, the air coming out of the vents feels warmer - but not much, and it takes a long time to bring up the temp of the house. When it's very cold at night, the unit runs all night long, blows cold air and the inside temp just keeps slipping.

The unit is switching ok from A/C to heat, and is not stuck in defrost mode - the defrost control and sensor were replaced less than a year ago. Evap coils were professionally cleaned just over a year ago. Beyond that, we have no clue. We've had servicemen out several times but they always get here when it's warmer outside and the problem seems to be fixed... until the sun goes down again.

Maybe it's worth mentioning that the A/C works like a champ. It was nice and cool in here all summer, even when the temps outside were over 110 several days in a row.

[Dan Webster]

Sounds to me like your aux or backup heat strips ain't workin. If the heatpump cannot reach the desired temp then the aux heat strips is supposed to kick in and finish the job on cold nights. Read more here:

How it works

Edited by applianceman18007260692, 04 November 2011 - 05:14 PM.

[RegUS_PatOff]

what's the outdoor night temperature
OR what's your location ?

[jumptrout]

I have heard of a number of weird operational features in this brand. Sounds to me like a reversing valve not functioning correctly if the unit works OK in the AC mode. It may sound as if it is reversing but not switching completely. What are the operating pressures in AC and Heat mode? What are the amp draws in Heat and AC?

[az_repair_gal]

Hi RegUs - I'm in Phoenix and we're at that strange time of year when we might need heat in the morning and A/C in the afternoon. We probably had a low of 48 last night, it's 55 right now and we're expecting a balmy high of 62. Thought this would be a good time to test things out. This morning the tstat showed the house at 64 degrees and it took about an hour to bring it up to 71.

Yesterday I replaced the old mercury tstat with a comparable dial model and it's coming on ok but shuts off when the inside temp is exactly 4 degrees lower than my setting. I had some questions about wire placement during install; I called Honeywell and got someone in India. I really don't want to call back to hear more reading from irrelevant scripts so if you have any ideas, it's Honeywell model CT87N. (No jabs about not going digital or programmable with the tstat, please! I like my old stuff and almost didn't replace it at all. I just did it because the tech suggested it. Also I used to play with mercury when I was a kid and so far I have not sprouted any extra appendages... )

Jumptrout - Replacing a tstat or tearing apart the washer/dryer are pretty much the limits of my ability. I have been on the roof many times looking at the heat pump and trying to understand its parts config, but I have to call someone out when it needs repairs. So I can't tell you what the operating pressures are. We just had a tech out last week who replaced the transformer and I'm certain it is switching over, but the air coming through on heat cycle is barely warm. Last January, it ran pretty much all the time and the temp in the house just kept dropping. Tell me more about the reversing valve - I thought you guys would be talking condensers by now...

[jb8103]

This isn't your fundamental problem but the CT87N is junk. I've had two bad off the shelf, one of them being five degrees off in the thermometer. Naturally it ignored set point temp until we were five degrees colder than indicated.

Take it back to Lowe's, go to a supply house and get the T87N. Not CT87N, but T87N.

I agree it sounds like an auxiliary heat problem. You better hope it's not the reversing valve. $$$ Get somebody up early and find out for sure.

[az_repair_gal]

Thanks for the advice on the tstat JB - will return it.

About how much is a reversing valve, if I may ask? And does the A/C working properly mean there's no issue with the condenser? A tech last year suggested the tubes might be clogged but I didn't completely follow his logic. I don't completely trust the techs who come out here - as you know, AZ is the place they film all those service tech stories for Dateline NBC, and rightly so. But this forum has never, ever steered me wrong.

[jumptrout]

Take the front cover off the stat. Look behind the front cover you will see a small slot on the temperature dial. You can adjust it right or left to coincide with actual room temperature.
The reversing valve is on the condenser. Its' purpose is to reverse the flow of hot gas refrigerant depending upon a call for heat or cool. Only high and low pressures taken from the service valves will tell you how the system is operating.
Is this R22 or R410a refrigerant? Is it TXV controlled or orifice controlled refrigerant flow?

[jumptrout]

When running in heat mode you can use your amp meter on a incoming power supply line at the air handler to determine if your auxiliary heat is assisting.

[az_repair_gal]

Thanks Jumptrout, we'll run some diagnostics and let you know what we find out.