Heat Pump - Constantly defrosts

[Bob CTS]

So this terror of a brand new heat pump is killing me. I have had the tech out two times for constant defrosts (uses demand defrost) He checks the charge albeit it was extremely cool that day in AC mode and says I have 9* subcooling (spec on unit plate says 9*), he says dirty air filter and replaced it. Same thing more defrosts. Comes out replaced defrost board Thursday, same thing again.

This happened when it was installed last year, tech added 1/2 lb of freon and never gave a problem, there was a leak in summer on the connection that was sweated (split unit), came out and fixed that in July, but I am still weary the charge was not checked properly as a severe storm moved in right as he finished the repair.

90% of defrosts are occurring with no frost. A heavy frost set in last night and I noted that only the lower half of the unit had frost and some horizontal coils had no frost.

Is this due to low charge?

Once ambient drops below ~40* I get probably three defrost cycles an hour.

Thanks

[mrvette]

Others here know more than I do, but when the outside coils get to a certain temp, and about 1/2 frosted can be in that temp region, the unit goes to reverse cycle, in other words....Air Conditioning mode....so you have two options as a designer....heat the outdoor coils to melt the frost off them and and shorten the indoor cold cycle, or heat the indoor air after the evaporator/blower coils with resistance heat....in the reverse/ A-C mode....

you can easy tell by the sound when they reverse cycle to defrost mode....they get noisy as hell and sound like a .22 caliber machine gun....

I suspect it's normal...

IMO, drill a well and go for Water/Air HVAC it uses the ground water for a heat sink instead of the outdoor air, and works much better in winters and more efficient in summers.....

:cert:

[Bob CTS]

Others here know more than I do, but when the outside coils get to a certain temp, and about 1/2 frosted can be in that temp region, the unit goes to reverse cycle, in other words....Air Conditioning mode....so you have two options as a designer....heat the outdoor coils to melt the frost off them and and shorten the indoor cold cycle, or heat the indoor air after the evaporator/blower coils with resistance heat....in the reverse/ A-C mode....

you can easy tell by the sound when they reverse cycle to defrost mode....they get noisy as hell and sound like a .22 caliber machine gun....

I suspect it's normal...

IMO, drill a well and go for Water/Air HVAC it uses the ground water for a heat sink instead of the outdoor air, and works much better in winters and more efficient in summers.....

:cert:

I know it is going into defrost, the damn thing wakes me up every time. The issue is that last winter it initiated a defrost when it was iced up, now it goes into defrost at least every other heat cycle.

If I had to do this over again, I would have put a furnace in.