HP21-60-230-03 outdoor unit.
CB31MV-51 Air Handler.

I happens quite frequently. Ive reset it twice in the last week. I understand this can be related to 'air flow'. Not even sure what that means. Its a two speed unit and I have plenty of 'air flow' out of the vents. Is there something I can do to keep this from happening? Its done this for several years and the techs have verified the switch is functioning properly. What can I do to keep this from happening? Im about two 'trips' away from flipping on my emergency heat in the panel and calling it good for the rest of the winter. It does not do this on cooling mode (usually).

If its air flow, can I just increase the fan speed or something?

Im noticing this more now because I have new thermostats that do not call auxiliary heat until that absolutely HAVE to, that means this stat will run for an hour or more before kicking in, so I notice when its cold in teh house.

 

I'm not following you..... reset the pressure switch ? Where would that be ?

You have a heat pump with electric reheat coils..... is that correct ?

 

There is a switch in the outside unit that has to be reset if the head pressure on the compressor becomes too high. Maybe its temp based, but its soldered into the copper. So, it trips and the air handler will come on, but the compressor will not because you have to go outside and push the reset switch. Its to keep the compressor from exploding.

I have a heatpump with strip back up/aux.

 

Does this heat pump have a motorized zone control (or bladder) system on it?

 

It has a zone system on the ducts. It uses an Arzel system. Its a vacuum operated system. All of that seems to be functioning properly though. Thats the only zoning there is on the system and its not part of the heat pump.

 

It may not be directly connected to the heat pump but if it restricts airflow across the evaporator coil.... that could be causing your problem.

 

I agree with PJ.
This can be addressed with a barometric bypass which will dump air into a stairwell or some other "Neutral space" when half of the zones close.

 

I have a bypass that dumps back into the air handler, but also I have a 'wild zone' that dumps into the living room no matter which zone is calling.

Its just wierd because it runs for 3 days.....5 days....or 1 day and then trips out. I cannot determine the exact parameters and temps that cause it. Its been running since I made this post without issue.

 

Dumping hot air back into the return and running that air through your indoor coil is like running your AC on a 120 degree (or hotter) day.

Closing off 50% of the dampers without a bypass is like blocking half of the outdoor coil in the summertime while running cooling.

Carrier has a zone control that gives you "All Zones" as a control option.
That would be a great feature with this problem.

Is the indoor coil clean?
Are you using pleated filters that are very restrictive (3M)?
Theses factors could also contribute to this problem.

 

Yes, the coils are clean. I have a media filter that is replaced every 6 months. I use fiberglass filters in my return register to catch big stuff and prolong the life of the media filter in the air handler.

I do have an option on my board to open all zone dampers. So far, its still running without issue. I really don't know what causes it, sometimes it does it, sometimes it doesnt, but I think your assessment of dumping hot air back into the coil is right on.


When she dies, it will be the last heat pump my house has.