I have two electric baseboard heaters in my house that are both controlled by a single digital programmable thermostat (King ESP-230). I believe each heater is 1500w so 3000w total. Twice now in the last year or so, it got really hot in my house when I realized the heaters weren't turning off at the specified temperature. The thermostat would be set around 65 degrees, and the house temperature would get up to around 75 degrees as shown on the thermostat itself.
What's weird is the red light that indicates the heaters are on, will be off. Here's a list of what I tried, the last item being the one that eventually fixed the problem:
- Pushed the power switch on the thermostat itself to Off
- Turned the temperature down to minimum
- Shut off the heaters at the breaker, and turned back on
- Pushed the Reset button on the thermostat, and set the day and time.
Only after setting the date and time after a reset did the heaters shut off. Does this just sound like I need to replace a thermostat that occasionally goes haywire, or could there be something wrong with the heater wiring that's causing the thermostat to mess up? Both times this happened, it was around 9pm on a Sunday evening, but I would imagine that's just a weird coincidence.
Best Answer
It sounds like the relay contacts are fused, this is not uncommon with loads that are constantly switched, the fact that the controlls are saying the relay is not being commanded on but it is heating points to the relay. (It could also be a solid state relay these usually short when they fail, then if there is enough current blow the junction open). The fix is a DIY get a replacement thermostat, turn the circuit breaker off, install the new stat and turn the power back on. I try to get thermostats that have a much larger rating than I need, make sure to add the ampacity of both heaters and get a thermostat that has at minimum this value (I will pay more for a 2x thermostat so it will last longer).