Arkansas HVACR NewsMagazine January 2026

HVACR NewsMagazine January 2026

Tech News

you may need to multiply it by 1000 to interpret the reading on the chart. In this case, the ambient temperature was just above 77°F.

If you don't have a thermometer on hand, you can use the same method one could use to calibrate temperature clamps. Get a bowl of distilled water, fill it with ice cubes, allow it to sit for a little while (there should still be an ice-water mixture), and then put the thermistor in there. The resistance readings should correspond to the value listed for 32°F. We know it's 32°F because ice and liquid water exist together, and the temperature can't drop until we have 100% liquid. Just like refrigerant at saturation, any added heat goes towards the phase change. (That's the latent heat of fusion when a solid-liquid mixture is involved.) If the values don't match up (or aren't at least within a reasonable 1 – 2°F tolerance), that indicates that the sensor has drifted and will need to be replaced. It really depends on the situation. Let's say you have a wire rubout on a thermostat-type coil sensor and want to keep using the OEM board. In that case, you'd just replace it with the OEM part. However, if you're using a universal board (such as if the customer wants to upgrade a time & temperature defrost to demand defrost or there's an issue with the board as well), you will have to use the sensor type that comes with it. The bottom line is that these coil temperature sensors work in different ways, which we need to understand to diagnose them properly. This article was furnished by the generosity of Bryan Orr, HVAC School by Techs for Techs. We encourage you to subscribe to their podcast and articles at https://hvacrschool.com/ Can Thermostats Be Replaced With Thermistors (or Vice Versa)?