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$49 / month O.A.C Including Install

Heat Pump Defrost Mode Explained

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Heat Pump Defrost Mode Explained

Posted On: March 9, 2026

Heat Pump Defrost Mode Explained

If you’ve ever noticed your heat pump stop blowing warm air for a few minutes during winter, you might wonder if something is wrong.


In most cases, it’s completely normal.


Your system is likely running in defrost mode, a built-in feature designed to keep your heat pump operating efficiently during cold weather.


At Twintech Heating & Cooling, homeowners often ask about this process when temperatures drop.


Understanding how defrost mode works can help you recognize normal operation and know when it may be time to call for service.


Why Heat Pumps Need Defrost Mode


During winter, a heat pump pulls heat from the outdoor air and transfers it inside your home.


While doing this, the outdoor coil becomes extremely cold.


When the temperature outside is near or below freezing, moisture in the air can freeze on the outdoor unit.


Over time, frost or ice buildup can restrict airflow and reduce the system’s ability to absorb heat.


If left unchecked, this ice can significantly reduce efficiency and heating performance.


Defrost mode solves this problem by periodically melting the frost from the outdoor coil.


How Heat Pump Defrost Mode Works


When sensors detect frost buildup on the outdoor coil, the heat pump temporarily switches into defrost mode.


Here’s what happens during the process:


The system reverses operation The heat pump briefly switches from heating mode to cooling mode.


Hot refrigerant flows to the outdoor coil This warms the coil and melts the frost or ice.


The outdoor fan usually stops This helps the coil heat up faster to remove the ice.


Backup heat may activate indoors Many systems temporarily use auxiliary heat so you don’t feel a blast of cool air.


The system returns to heating mode Once the frost is cleared, normal heating resumes.


This process typically lasts 5 to 15 minutes.


Signs Your Heat Pump Is in Defrost Mode


Homeowners often notice a few changes when the system enters defrost mode.


These are normal and expected.


Common signs include:


Steam or vapor rising from the outdoor unit


The outdoor fan stopping temporarily


A brief pause in warm air from vents


Clicking or whooshing sounds during the cycle


Auxiliary or emergency heat turning on


The steam you see is often mistaken for smoke, but it’s simply melting frost evaporating from the coil.


How Often Should Defrost Mode Run?


The frequency depends on weather conditions.


Your heat pump may enter defrost mode:


Every 30 to 90 minutes in very cold, humid conditions


Occasionally during normal winter weather


More frequently when frost buildup happens quickly


Cold, damp climates tend to trigger more defrost cycles because moisture freezes more easily on the outdoor coil.


When Defrost Mode Might Signal a Problem


While defrost mode is normal, excessive icing or constant defrost cycles could indicate an issue.


You may want to contact Twintech Heating & Cooling if you notice:


The outdoor unit completely covered in thick ice


Defrost mode running very frequently


The system struggling to heat your home


Ice remaining on the unit after the cycle finishes


The heat pump shutting off unexpectedly


Possible causes can include restricted airflow, low refrigerant levels, or a malfunctioning defrost control board.


Tips to Help Your Heat Pump Run Efficiently in Winter


A few simple steps can help reduce excessive frost buildup and keep your system running smoothly.


Keep snow, leaves, and debris away from the outdoor unit


Maintain at least 18–24 inches of clearance around the system


Change indoor air filters regularly


Schedule seasonal HVAC maintenance


Avoid covering the heat pump during winter


Regular maintenance ensures the defrost system works properly when your heat pump needs it most.


Professional Heat Pump Service


Defrost mode is an essential part of how heat pumps maintain efficiency during winter.


When the system is working properly, the process happens automatically and quickly clears frost from the outdoor coil.


If you’re concerned about frequent icing or reduced heating performance, the team at Twintech Heating & Cooling can inspect your system and make sure everything is operating correctly.


A well-maintained heat pump will keep your home comfortable throughout the coldest months while running efficiently all season long.



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See What Our Customers Are Saying:

by Private User on Twintech Heating and Cooling

Our hot water tank died and with an after hours phone called Bob the sales guy jumped into action. Friendly, courteous and genuinely wanted to do whats best for our house hold we were given options and he awaited an answer with no pressure.

We decided on what we wanted and it was installed asap and Greg and team worked and cleaned up so well, you would never know there was a hot water tank there before!

We love our hot water tank and being able to have back to back to back showers without having to wait for the hot water tank to heat the water!

by Gary Grieves, Ajax on Twintech Heating and Cooling

I had heard of Twin Tech from a good friend of mine.
I needed to get a new Air Conditioner. It was not working properly and was 19 years old. I decided to get a new furnace at the same time.
I gave them a call on Saturday June 28.
I spoke to Bob Graham. I made arrangements for him to attend my house the following day.
I saw him on Sunday June 29 at 1100 AM.
He was on time and looked professional.
He spent 2 hours with me going over what I needed. He also suggested that I purchase a Humidifier. He gave me a quote of just under $11,000.00 for the purchase and installation of a Air Conditioner, Furnace and Humidifier. He was not pushy and gave me time to speak to my wife.
I called Bob on Monday June 30 and made arrangements to have it installed by the end of the week.
On Friday June 3 they arrived at 830 AM.
Again, right on time.
Greg and Mitch worked all day and finished the installation by 430 PM.
They made sure that everything was working properly and the basement was just as clean as it was before they came.
I will now be using Twin Tech to perform any maintenance needed on this equipment.
I was completely satisfied from start to finish with the service provided.

Thank You,
Gary Grieves.
Upchurch Ave.
Ajax.

by Kevin, Toronto on Twintech Heating and Cooling

We contacted TwinTech after having another ductless air-conditioning company come in to quote on a solution for our townhouse. We had a unique problem where my office was a hot spot - it's at the front of the unit and gets a lot of sun. If it's 20C outside, It's 29C in my office. The other company could not build a solution that would get a ductless unit to that room because of the location - the AC unit would have to be at the rear, and ductless systems would have to be on that side of the interior. TwinTech suggested a hybrid solution to fit our unique problem, where the ductless unit would move cold air to an air exchanger installed in our bedroom closet, and then they built a ducted vent system between all the upper rooms. This was less intrusive than building a central air system, and less expensive. Each room has a vent that I can close off, so I can push more cold air to my office when needed. We really didn't want ductless units sitting on the walls, and this looks and works better. I really appreciate the extra thought and care that went into the design of a solution, and the attention to detail in the installation. They answered all of our questions, and were able to do a bit extra by installing the ducts around the vents and painting them for us. It cost more than we originally planned for, due to our unique needs, but the fact that they offered financing helped us budget for more.
The job was done fast (I think we got lucky with timing where it wasn't the AC install busy season yet), and the team was very friendly and professional. They arrived and finished each day when they said they would. My office is now running at a comfortable temperature! I'm extremely happy with the experience and would whole heartedly recommend them.

by Private User on Twintech Heating and Cooling

How lucky are we to have this team come save us from our broken down, under sold, poorly installed previous unit (mind you there is a reason SEARS went bankrupt). Bob arrived on time to give us a detailed review of our unit and furnace; very knowledgeable. Greg arrived as planned with the new unit and reiterated what Bob explained how our furnace is equipped to handle the new unit and we didnt need to spend more money on a variable speed air conditioner. Cant say enough on how professional, efficient and personable this team is. Thank you so much guys!

by Private User on Twintech Heating and Cooling

We used Twintech for our replacement AC. Bob did a great job assessing what we needed and organized the install and showed up on install date. Greg and Mitch were on time and were very neat. They covered the traffic areas with a drop cloth and did an excellent install. Great clean up after install complete. Would recommend Twintech for heating and cooling.

by Private User on Twintech Heating and Cooling

They were fantastic, clean, freindly, great service. Would definitely recommend. Answered ally questions and more.

by Private User on Twintech Heating and Cooling

We woke up at about 7 a.m. the Sunday morning before Valentine's Day to a house that was barely 15 degrees Celsius on a really cold day. We tried to call some other suppliers but no answer or call back. We did a quick google search and Twintech came up. Had never dealt with them before. They had a chat line and lo & behold, someone answered; Greg. Helped us diagnose that our 40 year old furnace pilot light was out and walked us through how to relight it. All worked well; he even called me during this process. No charge I was told when asked.
15 minutes later, the pilot went out. It would not stay lit. Greg had Bob call us and we set up a meeting for about 11 a.m. that same Sunday.
Bob walked us through the options and even brought 3 electric space heaters for us to use. By Tuesday afternoon, we had a new Furnace and central air installed.

The team was helpful, responsive and respectful. Very glad we found them by accident and looking forward to a nice cool summer after a warm winter.

Thanks guys!

by Furnace And Humidifier Install on Twintech Heating and Cooling

Dealing with Bob and the installation crew was a pleasure. They took the time to explain everything. What would benefit us the most and the price difference. They were in and out in a reasonable time frame and fit us in within a couple days of original meeting. Quality of work is excellent as well.

by Private User on Twintech Heating and Cooling

A pleasure dealing with Bob ,Spencer and Mitch . They are professional and they also observe the covid 19 precautions . Bob explained the whole process and got the new furnace up the next day . Highly recommend

by Gary Monson, Ajax on Twintech Heating and Cooling

Would like to thank TwinTech for their quick response to our furnace repair. We used TwinTech to install a new furnace and AC a few years
back. Our furnace started to have problems early in the evening of extremely cold night. Contacted TwinTech and they were able make a service call later that evening. They got the furnace going and came the next day to replace a part. The part was under warranty and there was
no charge for either service call!
We are extremely happy with their customer service and would highly recommend them.
Gary & Kelly

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See What Our Customers Are Saying:

by Aaron on Twintech Heating and Cooling

We are very happy to recommend this company to everyone. Our furnace broke down on Sunday morning. We phoned them and before noon Grant the owner showed up. He worked on the furnace for about a hour not wanting to give up to fix the problem. The furnace was 17 years old. I was the one talking about replacing it. End result was the next day it was all done. On the Sunday Bob came over with heaters to warm up the house. We decided to replace the water heater at the same time. Thanks Grant for the excellent work. Thumbs up.

by Linda on Twintech Heating and Cooling

Right on time. Explained how to work the HRV in a different way so the house would not be so dry. Changed my whole house water filter for me as well. Friendly, helpful, caring service!

by Robert Rogers on Twintech Heating and Cooling

Very pleased with the professional service that TwinTech Heating and Cooling provided in replacing my furnace. I got several quotes from different service providers. Their price was excellent and they explained the features very well. We are very glad we went with TwinTech and highly recommend their services.

by Robert Mizuno on Twintech Heating and Cooling

We were new homeowners in need of a second opinion. TwinTech Heating & Cooling were Amazing and professional. Very knowledgeable and great service all around. Recommend to anyone looking for honest and reliable services. Treated with respect and care. Thank you Greg, Mitch and Bob!

by Ruth on Twintech Heating and Cooling

TwinTech is an excellent and honest company! I called them for a second opinion after being told by another company that I needed to replace my furnace. Turns out this was not the case at all! I did not need a new furnace. TwinTech did not push to make an unnecessary sale and saved me from a huge expense. Bob and Mitch were extremely professional and above all honest! I definitely recommend TwinTech!

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