Question

question 39
why does ice build up on the outdoor section of the heat pump?
the heat pump is faulty
the cold outdoor air has high relative humidity
the outside temperature is too cold for the heat pump to be operating
the refrigerant charge is low
the system is locked in the cooling mode rather than the heating mode

Explanation:

When cold outdoor air with high relative humidity comes in contact with the cold outdoor - section of the heat pump, the moisture in the air condenses and freezes, leading to ice build - up. Other options like a faulty heat pump, low refrigerant charge, wrong operating mode, or too cold outside temperature are not the most common reason for normal ice - build up due to moisture condensation.

Answer:

The cold outdoor air has high relative humidity.