On a crisp winter morning, our office regularly receives phone calls from concerned customers regarding their system not functioning correctly. After our staff hears the situation and explains the defrost cycle of a heat pump, several customers realize their systems were functioning properly after all! 

Many people are unfamiliar with the defrost cycle of a heat pump. This article will explain what the defrost cycle is, why it happens and when you need to call to have your system checked. 

What is the defrost cycle of a heat pump?

The defrost cycle can occur when the temperature of the outdoor coil drops below 32 degrees. This happens because at this temperature, frost can form on the coil, which could cause damage to the system if left to build up. 

The system automatically switches itself to the cooling cycle to increase the temperature of the outdoor coil. You may hear the sound of the reversing valve switching the system from heating to cooling. 

Also, you’ll notice the outdoor fan is not running. The unit will only run in defrost for an interval of time. It should not affect your indoor temperature. The system will keep switching from the defrost cycle to normal operation until frost on the coil is no longer a threat.

Signs your heat pump is in the defrost cycle or experiencing issues

The defrost cycle of a heat pump is a valuable process. It is not unusual on a frigid evening or morning for your system to go into the defrost cycle several times. You should start to recognize the defrost cycle’s characteristics. 

As mentioned earlier, when the defrost cycle of a heat pump begins, you may hear the outdoor unit’s reversing valve switching from heating to cooling. Also, you’ll hear your indoor unit running, but the outdoor fan will be off. If you hear any new unusual sounds, or notice any other functions out of the ordinary you should have your system looked at.

Another reason to have your system looked at is if it is running in the defrost cycle during mild temperatures. As mentioned before, the defrost cycle of a heat pump should only occur when the coil temperature drops below 32 degree (not the outdoor temperature). 

If it is a 60-degrees day, your system should not be going into the defrost cycle. Also, if your system is running in the defrost cycle for an extended period of time there might be an issue. A normal defrost cycle of a heat pump on average will only last for five to 15 minutes until it switches back.  Give O’Brien a call to diagnose any concerns you may have about your system running in defrost.

We hope this helps you better understand what the defrost cycle of a heat pump is, when it occurs and why it takes place. If you have any questions regarding the defrost cycle of a heat pump please don’t hesitate to contact our office. 

And remember on a chilly winter morning, don’t be alarmed by the defrost cycle signs. Your system was designed to use the defrost cycle!          

O’Brien Service Company is a certified Trane Comfort Specialist and works on both residential and commercial systems. The company’s highly trained and versatile technicians can expertly handle complex repairs and installations, and provide advice on the benefits of regular maintenance. To arrange a free at-home consultation, call (910) 799-6611, or visit the company’s website at www.obrienservice.com.