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  • Writer's pictureRebecca Weaver

Heat Pumps: Defrost Mode Importance and Identification

Updated: Jan 19

We often hear "My heat pump is smoking and making a terrible noise!" then we arrive and the heat pump is working perfectly fine. The customer probably caught the unit in defrost mode and panicked- but don't worry! We'll help you recognize the signs of defrost mode in your heat pump.
Heat Pumps Enter Defrost Mode For 3 to 5 Minutes

We get so many calls about heat pumps turning off in the middle of winter's coldest days.


Homeowners are frantic as they try to figure out what could be going wrong with such an expensive piece of equipment- and we're right there with you!


Heat pumps are an excellent source of energy-efficient heat, though they weren't always the answer for Americans up north. As the technology has developed, heat pumps have become resistant to the harsher winters in the Midwest, making them a popular option for homeowners looking to lower their energy bills. For more general information about Heat Pumps, read our post about their history, benefits, and common issues: https://www.greenesplumbing.com/post/the-truth-about-heat-pumps.


If you notice your unit isn't kicking on for what seems to be a long time, don't panic just yet! When temperatures get excessively low, heat pumps need to defrost so they do not become one big block of ice!


Will My House Get Cold?

Chances are your heat pump is perfectly fine if it's demonstrating the signs we've listed because all of these signs are an indication that the unit has gone into defrost mode. Defrost mode does not last long, so allow the unit 5 or 10 minutes to kick back on. Once it's thawed out, it will go back to heating your home like normal. Typically, when your heat pump is in defrost mode, your backup heat should kick on to maintain a sustainable temperature in the home. If you notice the unit doesn't kick on for about a half hour or so, and the backup heat has not kicked on, but your inside temperature is dropping below your set temperature, then it's time to investigate.


The Importance of Defrost Mode in Heat Pumps:


1. Preventing Efficiency Loss:

Defrost mode gets rid of excessive ice buildup on the outdoor coil. Because the coil provides insulation to the unit, ice buildup can keep it from protecting the rest of the unit and cause key parts to freeze or work less efficiently. Defrost mode ensures the unit stays warm and efficient.


2. Maintaining Heating Capacity:

By periodically defrosting, heat pumps can keep providing warm heat to your home, ensuring consistent and reliable performance, especially in cold temperatures. Without defrosting, the unit would be working against ice and snow, which would cool off the heat before it was delivered to your home.


3. Comfort Control:

Because the heating capacity is maintained, efficient defrost cycles contribute to maintaining a comfortable indoor temperature, providing a seamless heating experience for users.


4. Preventing Damage:

Ice accumulation can cause damage to your heat pump. Defrost mode helps prevent this by melting the ice and allowing the unit to function properly.


5. Extended Lifespan:

By preventing damage to the unit and its components, regular use of defrost mode contributes to a longer lifespan for the system. It's important to make sure your heat pump is going into defrost mode during extremely cold temperatures, because it may cost you money in the long run if it fails to do so.


How to Identify Defrost Mode in Your Heat Pump:


1. Outdoor Unit Noise:

Listen for a change in the sound of the outdoor unit. A whooshing or humming noise may indicate that the heat pump is in defrost mode.


2. Steam or Vapor:

Look for steam or vapor rising from the outdoor unit during colder weather, signaling that the heat pump is actively melting ice. This is the easiest way to know if your heat pump is in defrost mode.


3. Cold Air from Vents:

Temporary cold air blowing from the vents indicates that the heat pump is redirecting warm air for defrosting. Normal heating will resume after the defrost cycle. Your backup heat should kick in if the temperature in your home begins to drop below the set point. This is typically done at 2 degrees below the set point but depends on how your thermostat is programmed. Some defaults are set to call for backup heat at 4 degrees below the set point.


4. Indicator Lights or Messages:

Check for flashing lights or specific messages on the thermostat or control panel that signal the heat pump is in defrost mode. When calling in any heat pump issue, make sure you know of any codes flashing. These can tell technicians exactly what's going on depending on the brand. Check your user manual as well, and see if it provides the light codes and their meanings.


Knowing how to identify defrost mode prevents unnecessary stress. If in doubt, feel free to call your trusted local professionals to see if there could be a greater issue. Ask them about defrost mode and how to know the difference between typical activity and signs of a problem.


Greene's is located in Tiffin, Ohio, and also services the surrounding areas like Fremont and Findlay. We'd love to answer your questions and help you better understand the equipment in your home!

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