Why does a heat pump defrost?

Question: Why does a heat pump defrost?

QuestionAnswer: When a heat pump is heating your home it is absorbing heat from the outside.  If the outdoor temperature and humidity reaches specific values the outdoor coil will begin to accumulate frost.  This frost eventually chokes off airflow and the system decides its time to melt this frost.  The heat pump reverses the refrigerant flow to warm up the outdoor coil and turns off the outdoor motor.  The system basically runs in cooling mode for about 5-15 minutes to melt the frost.  Most ducted systems have a back up heater to prevent cold air from blowing from the vents, other systems might slow down the indoor fan motor to limit the end user from feeling the effects of a defrost cycle.  For more information about Heat Pumps check out our blog at www.tempriteclimatesolutions.com

This question was originally published in the “Ask a Pro” column of the Comox Valley Echo.  Look for other questions fielded by Lance in the Ask a Pro column. 
Comox Valley Echo

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