Heat Pump Defrost Cycle: How Does It Work?

If you’ve been using your heat pump for quite some time, you may have noticed that it goes through a defrost cycle every once in a while. In today’s post, local HVAC service company ACS Air Conditioning Systems takes a look at the importance of a heat pump’s defrost cycle and how it works. 

How Do Heat Pumps Defrost?

Heat pumps are functionally air conditioners in reverse. When in heating mode, they pull heat from the outside air, which increases the likelihood of frost forming on the outdoor coil, affecting its efficiency. A heat pump with a defrost function senses when the outdoor unit falls below a certain temperature. It’s at this point that the defrost cycle kicks in and reverses the flow of refrigerant. After heat from the refrigerant has thawed the outdoor coil, the heat pump will switch back to the heating cycle.

There are some factors that contribute to how often air pumps switch to defrost mode. These include outdoor temperatures, humidity levels and the heat pump’s efficiency. Conditions that allow frost to form trigger the defrost cycle, which can happen as often as every 35 minutes. Most HVAC systems have a visual indicator, such as a blinking light, that indicates when the defrost cycle is running.

Things to Watch Out For

There are a few things which can indicate that the attention of your local HVAC installation technician may be required. Among these is that the defrost cycle shouldn’t kick in if outdoor temperatures are above 32 degrees. Nor should it be running longer than 5 to 15 minutes–the length of a typical defrost cycle.

Another thing to watch out for is if the heat pump is defrosting too frequently. If this has been happening since the first year after installation, the HVAC settings may be incorrect or there may have been an installation error. You can troubleshoot it yourself if it’s the former, but failing that, your HVAC technician should be able to correct the issue.

Call ACS Air Conditioning Systems

ACS Air Conditioning Systems is your leading provider of HVAC repairs and installation services. Give us a call at (925) 264-8040. You can also fill out our contact form to schedule an appointment.