Podcasts
Listen and learn while you drive.
Tickets On Sale For The 8th Annual HVACR Training Symposium!
PURCHASE TICKETS
Don’t miss HVACR’s main event—AHR Expo Chicago!
Explore the latest product innovations, industry trends, and best practices shaping the year ahead. Connect with leading manufacturers and discover solutions designed to solve workplace challenges and support your professional growth. Registration is free and includes access to everything HVACR—products, professionals, perspectives, and more.
Check out other formats
BRYAN ORR
Co-Founder and President at Kalos Services, Bryan has been involved in HVAC training for over 13 years. Bryan started HVAC School to be free training HVAC/R across many mediums, For Techs, By Techs.
Read more
Get Tech Tips
Subscribe to get free tech tips.
HVAC School – For Techs, By Techs
Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.
Why and How to Test Heat Pump Defrost – Short #310
In this short podcast episode, Bryan covers why and how to test heat pump defrost during maintenance. Heat pumps need defrost because the outdoor coil absorbs heat in heating mode. Moisture collects and freezes on the coil during this process, and the rate at which it happens depends on the temperature and the amount of moisture in the outdoor air. Frost interferes with heat transfer and airflow and must be defrosted; the reversing valve shifts and auxiliary heat turns on.
Before testing, identify the equipment brand and model, defrost control, and the defrost type (time & temperature or demand defrost); you may have a thermostat (open/close switch) or thermistor, and those have different operating and testing considerations. Some controls also allow you to accelerate timing.
Forcing defrost according to the manufacturer’s literature will let you discover whether the command sequence works, but it may not tell you whether the sensors are working. Common visual checks can also help you resolve defrost issues dealing with sensors, base pan heaters, and poor airflow.
The key takeaway is to pay close attention to the defrost sequence, conditions, defrost logic, sensor type, and your own spidey senses when testing or diagnosing defrost.
This episode contains embedded sponsor messages from Refrigeration Technologies, Carrier, NAVAC, Filtrete, and the 2027 AHR Expo.
Resources
- Learn Everything About Heat Pump Defrost (video)
- HVAC Defrost Troubleshooting | Timers, Sensors, and Boards (video)
- Heat Pump Defrost Cycle & Heat Strip Wiring Safety | HVAC Heating Season Preparation (video)
- How to Test Heat Pump Defrost and How Defrost Works (video)
- Upgrading Time & Temperature Defrost with Demand Defrost for Heat Pumps (tech tip)
- Heat Pump Defrost Troubleshooting Tips (tech tip)
- Coil Temp Sensors: Thermostats vs. Thermistors (tech tip)
- HVAC School calculators
- Submit a podcast question
- Learn about the GRIT Foundation
Purchase your tickets or learn more about the 8th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.
10/27/2026
10/08/2026
10/06/2026
Search Results placeholder
Follow Us On Social Media And Podcast Platforms
Check our latest Tech Tips
One aspect of motor selection that can get overlooked is motor bearings, and it can have big consequences. Sleeve bearings are most common in residential and light commercial applications because they are less expensive and quieter. They don’t have rolling “balls” but rather rely on a thin film of oil on metal sleeves. Sleeve bearings […]
Read more
All fuel-burning appliances require oxygen to burn. They require sufficient oxygen to burn cleanly and safely, without soot and CO (carbon monoxide). I see many open combustion furnaces jammed into tight closets and mechanical rooms with little thought or planning regarding combustion air. I live and work in Florida, where most of our fuel-burning appliances […]
Read more
An informed customer can make our job easier. When someone understands what they’re asking for, we can have a better conversation about what’s possible and what isn’t. Most customers who research a problem, including those who use AI, are trying to understand what’s going on. They’re willing to hear what they may have missed. Then […]
Read more
Download HVAC School App
