Heating in Cool or Cold Weather

The Need to Defrost

When outside air temperatures approach or drop below 50ºF, ice or frost may begin to form on the surface of the evaporator (the evaporator being the black, vertically-finned component that makes up three (3) sides of the heat pump).

• Ice and frost formation is a normal aspect of heat pump operation during cold weather.

• Before large areas of the evaporator can become disabled by ice or frost, a defrost cycle is initiated by the heater controls.

• No heat is being placed into the water while defrosting is under way.

Defrost Indicators

When defrosting, digitally-controlled heat pumps display an "FS" code, while analog-controlled heat pumps illuminate a "defrost" light.

There are Two Types of Defrost Systems

• ICEBREAKER® (heat & cool) models incorporate an active, hot-gas defrost system. During very cold weather, ICEBREAKER® heat pumps may defrost as often as every 50-minutes. The maximum length of time the heat pump will be in the defrost mode is ten (10) minutes/hour. While defrosting, steam may be seen rising from the heat pump—this is normal.

• Non-reversing (heat only) heat pumps use a passive defrost system to remove ice and frost buildup. Passive defrost heaters, when defrosting, simply shut off, permitting the frost or ice to melt.

Minimizing the Need to Defrost

Late night and early morning—generally being the coolest times of the day—are least efficient for heat pump operation. The need to defrost (during cool or cold weather) is a very good reason why heat pumps should be timed to operate—whenever feasible—only during the warmest, daylight portions of the day.