Heat Pump Frost Ice Buildup. Hi. I noticed my that one of my outside heat pump condensing units was laboring throughout the night. This morning I found ice frost buildup on the heat pump condenser fins. I live in Tucson, Az. It has been colder than normal (below freezing) with a bit more moisture in the air than usual as of late. Can you please tell me what causes this frost ice buildup, and how I go about rectifying? Does this mean that the condenser pump is shot? I’m originally from the Midwest, and have never experienced this before. What should I be doing? Thank you for your help.

Heat Pump Frost Ice Buildup - The Answer

Heat Pump Frost Ice Buildup

Inside a Heat Pump

It sounds to me like you have a heat pump. It is normal for frost to build up on heat pumps. I would guess that in Tucson they set the heat pump defrost cycle times pretty high as it is dry there. If you have a lot of ice build up on the heat pump then there is a problem. Possibly with the heat pump defrost controls. However, if the heat pump frost problem is just intermittent then everything is working fine. Therefore, it’s defrosting as designed.

Heat Pump Frost Ice Buildup - Defrost Methods

There are different methods of initiating heat pump defrost but by far the most popular method is timed defrost. The heat pump unit will run for an hour and then automatically kick into the defrost cycle for a predetermined amount of time as engineered by the manufacturer in the defrost control circuit. This is all solid state control by a printed circuit board. Many are the same from manufacturer to manufacturer.

There is no big difference from a Trane to a Goodman to a Carrier to Rheem heat pump as far as defrost controls are concerned. It is all in the heat pump sequence of operation and is controlled by the defrost board. On the heat pump defrost control board there is usually a jumper or dip switch setting where the heat pump defrost times can be changed depending on geographical location and the HVAC technicians professional opinion. Sometimes the switch or pins are set for 30 minutes and some of them are set for 120 minutes. It really depends on several factors as to where this switch or pin is set for time defrost considerations. If this time is not set correctly you can lose efficiency.

Heat Pump Frost Ice Buildup - Conclusion

Good luck, and remember if you think there is something wrong with the unit then it never hurts to have it checked out by an HVAC pro. It will give you peace of mind. Better a good heat pump check-up by an HVAC Pro can keep you from being cold late at night. See the video below for how a heat pump enters and exits defrost properly. It makes a noise and then the condenser fan shuts down. You hear a loud humming noise and then it is quiet for a while. Then you see the frost and ice melt off the heat pump unit. Finally, when it exits defrost mode you see the condenser fan motor start to turn again. Then a little steam from that process.
High Performance HVAC

Heat Pump Frost Ice Buildup

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