heatpumps

I assume you want the de-icing operation? If you checked the manufactures web site, asked customer service or had the prints from the electrical panel cover this would answer your questions. I'm not being a smart---. Each manufacturer is probably slightly different.

Good luck,

James

Below 32*f a heat pump requires a defrost cycle such as the following:

Defrost Cycle

Mechanical: In heating mode, the outdoor coil is the evaporator. Moisture from the outdoor air condenses on the cooler coil and normally runs off. During the colder part of the heating season, this moisture freezes and blocks air movement through the coil. The frost is removed in the defrost cycle.

1. The heat pump operates in the heating mode.

2. The defrost control detects the buildup of ice on the outdoor coil.

3. The reversing valve solenoid de-energizes, directing hot gas from the compressor to the outdoor coil to defrost.

4. The outdoor fan stops. If it didn't, cold air from the fan prevents the melting effect of the hot refrigerant.

5. As the temperature of the indoor air drops, controls energize the electric heat elements to warm the indoor air.

6. When the defrost control detects the ice has melted, it terminates the defrost mode.

7. The reversing valve shifts to the heating position and directs hot refrigerant gas to the indoor coil.

8. The outdoor fan operates.

9. The electric elements cycle off.

10. The unit is now in the normal heating mode.

Electrical: A defrost control must recognize when there is a layer of ice on the outdoor coil and when that ice must be removed. There are several different types of defrost controls. While they vary in the methods used to recognize when defrost is necessary, they all take the same action. These controls also must determine when the ice is gone and terminate defrost.

1. The defrost control initiates a defrost cycle when ice builds up on the outdoor coil.

2. The control energizes the on-board defrost relay with 24 volts.

3. The defrost relay contacts open to de-energize the reversing valve.

4. The defrost relay contacts break power to the outdoor fan.

5. The defrost relay powers the heat relay to bring on the indoor electric heat.

6. After the ice is defrosted, the defrost control terminates the defrost cycle by de-energizing the defrost relay.

7. The defrost relay contacts close sending 24 volt power to the reversing valve and the valve returns to the heating position.

8. The defrost relay contacts close sending power to the outdoor fan.

9. The defrost relay contacts open breaking 24 volt power to the indoor heating relay.

10. The heat pump is now in the normal heating mode.

Hope this helps your understanding of cold weather heat pump operation

Very good !

Lots of $$$

Heatpumps have an electric heater that heats as the outdoor air cools I am in northern North Carolina where it gets cold enough often enough that the cost of resistance heating becomes prohibitive. To overcome that we use Hybrid heat pumps. My system swithes to gas heat below 40. At that temperature the gas heats more efficent than the heat pump. The cost for this system is about15% more than a heat pump alone and the advantages are more than just energy saving.