is freezing up normal for a heat pump?

[greybeard]

1 other thing. The compressor itself was coated in ice as well when I first walked up on the unit that morning so I'm pretty sure it hadn't been cycling back to A/C mode.

 

[greybeard]

They have timers that can be set for 30,60or 90 minutes. We usually set them at 90. Doesn't mean it will go into defrost every 90 minutes but it will check to see if the defrost thermostat is closed to see if it needs to go into defrost. I've had people call me that's never owned one and think their unit is on fire because of the steam coming off of it or that their fan motor went bad because it shuts the outside fan off in the defrost cycle.

Where are these timers and the board usually located?
Are they where the relays and capacitors would normally be on a conventional central unit?

I do know that house was over run with mice and rats last year.

 

[Little Joe]

Where are these timers and the board usually located?
Are they where the relays and capacitors would normally be on a conventional central unit?

I do know that house was over run with mice and rats last year.

Yes, it'll be behind the service panel where the contactor and capacitor are. It should all be built in to the control board in there, the timer should have dip switches on the board to set the different times or a jumper that slides over 2 pins. The defrost thermostat will be attached to one of the tubes on the coil and will be wrapped with a black rubbery insulation. There's a way to test the defrost with a screw driver between 2 test pins but I wouldn't recommend it to someone not familiar with them as you might short out the wrong thing.

 

[simme]

1 other thing. The compressor itself was coated in ice as well when I first walked up on the unit that morning so I'm pretty sure it hadn't been cycling back to A/C mode.

Odd. Best I remember, one winding of the compressor is continuously energized so that the compressor is kept warm so that the refrigerant is kept from condensing when the compressor is not running. Power contactor only switches one leg of the 240 vac with the other leg always on. If the refrigerant in the compressor condenses to liquid, bad things happen when it tries to compress liquid. Was the power on? Both legs?
@Little Joe I know that low refrigerant can freeze the inside coil in cooling mode. Can low refrigerant freeze the outside cool when in heating mode? Been a long time since I had a heat pump.

 

[greybeard]

Was the power on? Both legs?

I assume yes, as the fan was running, but I didn't look at the unit close enough to see if both sides of the main contactor were closed.

Anyway, thanks for all the info. I knew nothing much about heat pumps before and a lot more now.

 

[simme]

I assume yes, as the fan was running, but I didn't look at the unit close enough to see if both sides of the main contactor were closed.

Anyway, thanks for all the info. I knew nothing much about heat pumps before and a lot more now.

Best I remember, the fan runs on 120 volt (one leg to neutral) and the compressor is 240 for sure. The power contactors in those are called 1 and 1/2 pole. One leg is just an unswitched feedthrough (what they call the half pole) with only one switched contact on the other leg. That unswitched side keeps the compressor warm when not running. Wonder if he is missing one leg of the circuit, running the fan and controls, but not the compressor. Just thinking without looking at a circuit diagram.

 

[Little Joe]

Odd. Best I remember, one winding of the compressor is continuously energized so that the compressor is kept warm so that the refrigerant is kept from condensing when the compressor is not running. Power contactor only switches one leg of the 240 vac with the other leg always on. If the refrigerant in the compressor condenses to liquid, bad things happen when it tries to compress liquid. Was the power on? Both legs?
@Little Joe I know that low refrigerant can freeze the inside coil in cooling mode. Can low refrigerant freeze the outside cool when in heating mode? Been a long time since I had a heat pump.

Yes, low refrigerant can cause the outside unit to freeze up in heat mode, the outside coil acts as the evaportator on heating mode and the inside becomes the condensor. The fan motor will either be 208-230 or a dc motor, many of the newer ones have dc fan motors because they are supposed to be more efficient, some have 208-230 going to the motor and the converter is built into the motor. As far as keeping the compressor heated, many models have a crank case heater either wrapped around the compressor or goes through a hollow spot in the bottom of the compressor, the purpose of the heater is to keep the oil in the compressor warm.

 

[greybeard]

Yes, low refrigerant can cause the outside unit to freeze up in heat mode, the outside coil acts as the evaportator on heating mode and the inside becomes the condensor.

that makes sense.