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Careful of Your Heat Pump After a Power Outage

Posted by Geordie Romer on March 17, 2021

The following is a guest post from Don Hester of NCW Inspections

Heat pumps are very common in North Central Washington towns like Leavenworth because of the need for air conditioning. Heat pumps combined with our lower energy rates can create a very low cost of operation for heating needs during the winter.

Heat pump after a power outage

Photo courtesy of Chan Bliss on Flickr

One thing that we all know though is that winter can bring many surprises. One surprise you do not want is a failure of your heat pump to fail after a power outage.

The advice that I am about to give can be given wholeheartedly and from personal experience.  This humble little home inspector has had the scenario described happen and caused the compressor in my heat pump to fail.

Every homeowner should understand that special care should be taken when turning the heat pump on after an extended power outage.

The refrigerant in the compressor takes time to warm-up before it can properly operate. If started cold it puts a very large demand on the system that can cause the compressor to fail. This is referred to as refrigerant slugging. This will be more critical in very cold conditions and as the unit ages.

During the power outage you want to want to switch the heat system into supplemental/emergency heat mode at the thermostat.

This will engage the supplemental heating elements in the furnace when the power returns.

You should wait approximately 6 to 8 hrs before switching back into heat pump mode after a power outage.  

Photo courtesy of Sean Dreilinger on Flickr

Carrier suggests that if the electricity to the heat pump has been off for more than 30 minutes switch your thermostat to EHEAT (emergency heat) mode before restarting your heat pump.  Leave the system in EHEAT mode for an amount of time equal to the power outage. If you cannot determine how long the power has been off, leave the system in EHEAT mode for 8 hrs. Lennox suggests running their systems for 6 hr before trying to engage the heat pump.   If after that period of time the heat pump does not work properly a call to your local HVAC professional should be made.

Every homeowner should make themselves familiar with the operation of their heating and cooling system.  Most system manuals can be found online.

For Carrier Systems-

For Lennox systems  – Literature and Manuals

Remember most manufacturers suggest a minimum yearly maintenance and preferable two a year during the heating and cooling seasons.

Don Hester of NCW Home Inspections, LLC  is a Licensed Washington State Home Inspector located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington.



    If you’re planning to buy a home in this area, the best place to start is with the Leavenworth Home Buyer’s Guide.

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