My Hot Tub Overheats

Stuck Thermostat

When you first realize your water temperature is too hot, try adjusting the thermostat setting to a lower level and waiting a while. If you check the water later only to realize it is still just as hot and not responding to adjustments, then you may have a stuck thermostat. Listen closely and you will be able to hear the heater kicking on and off as you turn the dial back and forth. If you can’t hear the click and hum associated with the heater coming on and off as you adjust the knob, then the heat is probably stuck in the on position and the thermostat will need to be replaced.

Another potential problem with the thermostat in a hot tub is the bulb. The thermostat bulb is connected to a copper wire and filled with Freon. When the bulb heats, the gas expands, and when it cools, the gas contracts. This expansion and contraction activates the switch that turns the heat on and off and helps maintain the proper heat level. If the bulb is corroded or otherwise malfunctioning, it may not be telling the system to reduce the temperature, and the water will get increasingly hotter. You cannot replace the bulb only and will have to replace the thermostat for this reason as well.

If you suspect your thermostat is the heat problem in your hot tub and you disconnect it only to find the heat does not disengage, then there is a wiring issue that is keeping the heat from turning off. The heat contactor is connected to the heating coil inside the system and the contacts are stuck in the “on” position. Disconnecting the coil from the contactor should stop the heating, and the contactor will need to be replaced.

If hot water is not your concern, but you are instead concerned about the pump overheating, you should check the area immediately around the hot tub pump. If there are objects blocking the ventilation of the pump such as leaves, chemical containers or other foreign objects, the pump may not be able to draw in enough air to keep the parts cool. Allowing the pump to overheat can do serious damage to the motor. Clear the area around the pump to be sure it is getting proper ventilation.