short cycleing at end of long run

[haw85209]

HI, i have a carrier heat pump 4 ton split system and this last week i have noticed that when i first come home and turm my t-stat from 87 to 84 the unit will run get to 84 and then while the t-stat is still calling for cooling the condenser will cut out and come back on 2 or 3 times real fast then shut off when t-stat satifies, when its 84 in the house and its just maintaining that it just shuts off normally, no short cycle. indoor blower is set to auto and stays on while condenser cut on and off. i have already changed the t-stat and it still does it, what do you think, i live in az and it only started doing this since its been over 110 outside

thank you

[haw85209]

oh yea its a 410 a system, when its 84 in the house it runs for about 10 min and shuts off , when its 87 and i put it to 84 when i get home it runs about a half hr or more to get to 84 , i set it to 87 when i go to work and 84 when i am at home

[wormy]

possible high pressure safety switch opening trying to protect the equipment from high refrigerant pressures.


110 outdoor temp AND 87 degree indoor temp will cause the refrigerant pressures to be VERY high.
(At least it would be here in TN. Indoor humidity is a factor in that as well.
We've got lots of humidity here.)


IF it is the high pressure safety opening and closing, then I'd suggest adding a
compressor cycle timer as well. If a safety switch opens and closes real fast, the timer will make the compressor wait 5 minutes before coming back on.
Compressors don't like turning off and on real fast.

Since I'm not from AZ, I can't give you really GOOD advice.
But I'll throw in what I can...
I'd try leaving the indoor temp set for 84 during the extreme outdoor weather.

Spraying water on the outdoor unit while its running will lower the pressures.
BUT ! ! ! ! ! AZ water might not be the best thing to be running on the coils. I couldn't imagine what it would do to your coil.
I drank some New Mexico water when I was a kid... almost threw up.
Went on a trip to AZ about 20 yrs ago with a friend.... told him not to drink the water.. he didn't listen to me. He turned all kinds of shades of green.

[haw85209]

thank you wormy, i am going to leave the thermostat at 84 all the time from now on and see what happens, i was just trying to save a few bucks by turning it up when i am not home,