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Temperature controller question


AC Members
I have a heater plugged into a temperature controller now. The controller turn the heater off at 78°F and turns on at 77°F. The thermostat on my Eheim heater is set to 80°F, as a backup, in case the temperature controller fails.

With this setup, the thermostats stays closed or "on" 100% of the time. Is this a bad thing for the thermostat? Can it get stuck in the on position from constant contact like this?

I understand that the temperature controller is controlling the temperature. But if it should fail in the on position, and it's been this way for years, does this increase the chance of it getting stuck in the on position?
I personally don't think there will be an issue, but anything is possible.

It shouldn't be an issue for the thermostat within the heater, and even if it did, any externally controlled heater will always be on anyway, so it is really the norm.

you should take the normal precautions, such as not having a heater that is too large for the volume of water... that sort of thing.


Global Moderator
Staff member
I wouldn't think the constant on of the heater T-stat would be an issue. The way I think about them, it's the cycling on/off, arching and mechanical movement that makes them fail.