UPDATED 11/19/2025
As temperatures start to dip, it’s easy for certain HVAC maintenance tasks to slip your mind—especially the ones that don’t demand attention until something goes wrong. One item you don’t want to overlook this season is your freeze stat. If you need a reliable replacement, we offer a range of freeze stat options that you can easily install or keep on hand. Before winter fully settles in, take a moment to confirm these controls are functioning properly. A few quick checks now can prevent costly headaches later.
What are Freeze Stats?
According to The Air Conditioning, Heating and Refrigeration News, “The freeze stat is a safety switch that is used in almost all commercial and industrial air-handling units, cabinet unit heaters, unit ventilators, and blower units that have chilled water and/or hot water coils.” In short, freeze stats and low-temperature cutout controls exist to protect your coils from freezing and rupturing.
Testing them isn’t as simple as pressing a button. Because freeze stats rely on copper sensing tubes filled with temperature-sensitive gas, any kinks, cracks, or damage from installation or handling can compromise their accuracy. That’s why a careful, hands-on test is essential to ensure these controls will respond properly when temperatures drop.
Here are some steps on how to test your controls:
Step 1. Make sure they are installed in the correct location—directly downstream of the hot water coil (upstream of your cooling coil) in a horizontal serpentine fashion, spaced evenly across the coil. This location will prevent false trips and provide full coil coverage.
Step 2. f the freeze stat comes with an adjustable temperature setting, set the temperature as low as you feel comfortable without dropping below freezing (35°F is typical).
Step 3. Buy freeze spray, such as our freeze stat test spray, or ice and physically apply to 12 ̋-18 ̋ of the serpentine copper tubing that holds the temperature-sensitive gas vapor. The gas vapor pressure will drop and cause the freeze stat to trip.
Step 4. Verify the sequence of operations that occurs or that is supposed to occur when the freeze stat trips. This will typically include a shutdown of unit fans, closing of the outdoor air damper, and an opening of the hot water valve.
Step 5. Once complete, you will need to reset the freeze stat if it does not do so automatically. In some cases, you may need to physically reset the freeze stat as well as clear any front-end alarms that have been programmed to prevent the unit from automatically restarting after a freeze condition.
Kele has freeze stats and can offer technical advice to make sure your system is ready. Give us a call at 877.826.9045 if you have specific questions about your job or need help finding a part. We are ready to help.
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