HVAC FAQs - Heat Pumps

When a heat pump operates normally, ice forms on the outdoor coil. To melt the ice, the heat pump periodically initiates a “defrost cycle.” During the defrost cycle, the outdoor fan shuts off, and the coil warms up to melt the ice. Because the fan is off during the defrost cycle, the heat pump sounds different than during normal operation. Towards the end of the cycle, the coil will be warm enough to evaporate the moisture on the coil, and steam can be seen coming from the top of the unit. The defrost cycle lasts about five minutes after which the heat pump returns to normal operation and continues to heat your house.

Heat pumps form ice on the outdoor coil during normal operation. The heat pump should defrost several times per day, depending on outdoor conditions. If the system that triggers the defrost cycle is malfunctioning, a heat pump will simply continue to build ice (several inches thick) without ever defrosting. Also, low refrigerant levels can prevent the defrost cycle from melting all the ice. If your heat pump is not defrosting, get professional heat pump service before the icing damages your compressor.

A heat pump is very similar to an air conditioner. In the summer, an air conditioner uses its compressor to circulate refrigerant through copper pipes. The refrigerant absorbs heat from the home and releases Heat it to the outdoors. A heat pump has a “reversing valve” that reverses the flow of refrigerant in the winter to absorb heat from the outdoors and release in inside. The control of the reversing valve determines whether the heat pump heats or cools your house. Modern heat pumps produce heat three times more efficiently than a resistance-type electric heater. Want to learn more about heat pumps? Check out our blog on Heat Pump Operation.

The average life span for a heat pump is 12-15 years. This can be extended by proper indoor-outdoor system matching, proper installation, and regular maintenance.

Older heat pumps produce register temperatures of 80 – 90 degrees. While 90 degrees sounds warm, it actually feels cool when you put your hand over the heat register because the air is moving quickly. Newer heat pumps (built in the last five years) with variable speed blowers produce higher temperatures in the 100-115 range. This is very close to the 120 degrees produced by a modern gas furnace.