And how do you know they are not heating? What does your thermometer say the water temperature is? Compare it to the room temperature. If a heater is not heating, the thermometer will indicate the water is the same as the room temperature or just a degree or two higher. Or it may read that the temperature is warmer than room but more than two degrees less than the heater. Heaters should heat the water to within the temperature they are set at, plus/minus 2 degrees. So if you set it at 80, the thermometer should read anywhere from 78-82 to be accurate. If your room is 72 degrees, and the water is 74, the heater is heating, but not accurately. If the room is 72 degrees and the water is allegedly 66, that is a thermometer issue.
Date published: 2019-02-04