The reset button on our electric water heater keeps popping out and shutting down the heating element. When I reset it, the heater works for 24 to 48 hours until the button pops out again. What’s happening here?
Check the elements. One or both could be burnt out so that they overheat the tank. If they are both good, then one of the thermostats is malfunctioning. Probably the upper one, especially if it is a “non adjustable” one.
Your problem is either the upper combo limit/thermostat or lower thermostat. You need to reset limit, let heater warm up for an hour, than CAREFULLY, with the power on, turn up upper thermostat and see if you have 220-240 volts to upper element (should be). Turn thermostat down and you should read 0 (even though element has 120 volts to it). Now do the same with the lower thermostat (must leave upper thermostat turned down). If either reads 220-240 volts with thermostat turned down, that one must be changed. If you are not comfortable working with electric or don’t fully understand this explanation, call a qualified plumber or electrician.