Causes of Frost Bands on a Heat Pump

Frost bands are areas of frozen water that appear on heat pumps. Heat pumps, like air conditioners, have both inside and outside components to move warmth from the outside air to inside areas. Heat pumps are efficient and are dependable in warm weather, but they can suffer from freezing problems when the temperature drops. If you have a heat pump and it is malfunctioning in the cold weather, you can look for a variety of frost issues.

Common Weather Conditions

Heat pumps do naturally develop bands or areas of frost on the top of their outdoor components. This is a natural effect caused by the drop in temperature. When heat pumps encounter this frost, they enter a defrost cycle, in which they act as air conditioners and carry heat away from the house to melt the frost that has settled on top of the unit. If this defrost cycle fails or its timer malfunctions, the frost may start to build more thickly and create serious problems.

Extra Moisture Present

Extra moisture may also create bands of thicker ice across the heat pump. If you notice a band of ice, try looking up. If your roof does not have gutter, rainwater could be falling along the top of your unit from the roofline and freezing there. Freezing rain weather conditions can also cause a pattern of frost on your heat pump.


Refrigerant Issues

If the refrigerant levels in your heat pump are incorrect, the result is often frozen areas, especially frozen coils or frozen water near the coils. Too much refrigerant causes the heat to move to slowly through the system so that it cannot warm the right coils fast enough, causing frost. Too little refrigerant and the heat pump can draw heat away from coils too quickly, causing frost to form.

Blocked Coils

Sometimes outdoor coils for the heat pump can become blocked by leaves or debris. This is much like having a refrigerant problem. The transfer of heat will be impaired and the heat pump will grow too cold too easily, freezing nearby moisture. This is one of the easiest problems to fix and keep from occurring, as long as you keep your heat pump unit clean.