Heat Pumps and the Defrost Cycle

     When the temperature starts to drop and you switch to the Heat mode, your A/C Unit does some things that often causes alarm.  Heat pumps have a normal defrost cycle that causes the unit to do things perfectly normal, so no need for alarm.

     The most common concern is, "My outdoor (condenser) unit is smoking."  While it may appear to be smoke this actually is steam and this is a normal part of the defrost cycle.  This cycle is necessary for the unit to melt any ice that forms in the outdoor unit.

     The defrost cycle happens in cold temperatures and lasts for less than 15 minutes. The unit may go into defrost cycle every 30, 60, or 90 minutes as needed. You may also notice water dripping off the condenser; this is just the melted ice.  You may even notice ice on your condenser; once the defrost cycle kicks in the ice will melt.

     While in defrost you may hear noises often described as: clanking, humming, vibrating or thumping.  Again this is normal for the defrost cycle.

     If you experience any of this and you are maintaining the desired temperature, you can relax knowing that your unit is behaving as it should.

     Also normal but again a frequent cause for alarm is, "I turned on the heat and it smells funny."  In defrost cycle, the condenser will stop running, in order to maintain the desired temperature the heat strips will turn on and the system will run in "auxiliary heat" until the defrost cycle is over. This is very normal the first time you use your heat or if you haven't used it in awhile.  Dust has accumulated over the year and what you smell is that dust being burned off.

     A side note about the heat strips, on an extremely cold day they may turn on with the heat pump when the unit is NOT in defrost cycle to assist the heat pump in bringing the temperature up in your home.

When should you be alarmed?

     If you notice the steam or 'thumping noises' last more than 15 minutes - call us and schedule a service call.

     If the condenser is covered in ice, and the unit has not gone into the defrost cycle - call us and schedule a service call.

     If the unit is not maintaining the desired temperature - call us and schedule a service call.

     The heat has been on all day and it still has a foul smell - call us and schedule a service call.

Energy Saving Tips:

     If you are concerned about saving energy we recommend a programmable thermostat - this allows you to set your desired temperatures for the day, the evening and while you are sleeping.

     If you do not have a programmable thermostat and want to conserve energy it is recommended to lower your thermostat by 2 degrees before going to bed.