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Heating, Air Conditioning, Fridge, HVAC/Central heat and air freezing up in winter


I have a rheem central heat and air unit. While running the heat when it gets below freezing outside the unit is  freezing up. The air flow is fine the unit is clean no damaged fins. What is the problem?

There is no problem.  Ice build formation is normal for a heat pump running in heat mode.
Generally speaking, heat pumps start to loose their ability to heat indoors once the outdoor temp drops below the mid 30's.  The temp and humidity outdoors determine how quickly the ice will build up.    The unit has a defrost controller in it to melt the ice which is based on time.  If the ice is getting too thick, then the defrost may need to happen more often.  There is a setting on the defrost board located in the outdoor unit.  


Heating, Air Conditioning, Fridge, HVAC

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Craig HVAC Expert


I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.


I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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