old Heil heat pump - question

[redsox]

Im new here so if this has been posted before accept my appologies and redirect me please. I use a ICM300C defrost board on my old Heil heat pump. I bought a new board last year and set it up " stare and compare" When the temp drops below 40 it wont come out of defrost and the only way to reset the board is to kill the dissconect for 30 seconds- is this the way they run? what should the board be set for? the old board did the same thing might it be a bad board- summer is fine - its only at that temp in the defrost cycle- thanx folks and merry holliday

[HayZee518]

heat pump

I hope you know that a heat pump works like an air conditioner, only backwards. That's the reason for a reversing valve.
An air conditioner's cycle has an evaporator, compressor, fans and condenser coil. The condenser in a window unit exhausts heat laden air out to the atmosphere. In a heat pump, the condenser could do just the same or give off heat laden air to a ground loop.
When its in the heat mode, heat is circulated through the evaporator which normally passes cool or cold air to the room(s).
The condenser removes ground heat through the loop and hot freon goes to the evaporator to be given off.
The defroster is a coil mounted under the evaporator coil that heats up a little to remove any ice build up in the evaporator.
Actually I don't see why they use an aux heater for the evap as it will be passing hot gas.
There is also a heating element in the case of a central air conditioning unit to supplement the evaporator heat output. These have banks of heating elements that operate off sequencers depending on the amount of heat required.
I would think the defrost stops after a time delay as it depends on an external thermostat to detect outside air temp.

[HayZee518]

heat pump

did a little bit of searching and found these three videos on the defrost of a central airconditioner heat pump.
Not the same as yours but maybe will give you some insight as what to do.

Heat Pump Repair - Defrost Control Board - Stewart's Cove DIY - YouTube
Heat Pump Defrost Board : Diagnostic Procedures (Forced Defrost) | Louisville Kentucky HVAC Repair - YouTube
Heat Pump Defrost Board : Ambient & Coil Sensor Test - YouTube

http://www.youtube.com/watch?v=PY2i4JTmZHY

[redsox]

Heil heat pump

Thanx- but this HP has no haeter coils at the cond unit, perhaps the old style crankcase htr. The problem is the board doesnt come out of defrost. I used to do alot of this years ago. It gets a 30, 60, 90 minute run in heat- then usually 10 minutes in defrost. You can hear the RV kick over but when it 'times out' it doesnt reverse so -it 'kicks out ' the comp and just runs the evap fan and boy does it get cold. Why it doesnt engage the reversing valve at the lower temps is my ? it does until you reach the low 40's is this the design The old lady who used to own this house had the htr coils in the evap xconnected at the tstat cause of $ or dangerI wont run them cause those elements havent been juiced in year - after reading everything I found a new board for 20$- so Ill see - I may have made an error the first time- thanx anyway and merry xmass