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I have a 2 year old 4" submersible well pump which sometimes triggers the thermal protection. If I turn it back on, it continues to run properly and at some point (could be hours, could be days, could be weeks) it triggers the thermal protection again.

It never happens to trigger the thermal protection immediately after I just reset it.

Could it be a faulty thermal protection ? Or could it be something else ?

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    Low water levels will cause the pump to overheat usually once they kick out the well has had time to recover (fill back up) and cool the motor. Have you had a flow test on your well? A pump that is a bit oversized can cause this problem. Also new homes in the area can lower the static level because of increased usage. These are things that I have found in the past that contributed to random trips. If it becomes a regular issue or tripping on start check the starting capacitor(s) a bad cap can cause overheating in the start circuit and the run circuit if your system has both. – Ed Beal Jun 5 '17 at 18:43
  • Thanks @EdBeal , I haven't considered a flow test, I'll look into that! So far the trips have been random. Works for tens of minutes at a time while watering the garden, then tripping, resetting the breaker and then continues to work for other tens of minutes or even days. Today it tripped 3 times, and last time it tripped was over a week ago. It even tripped during heavy storms so I'm not sure if well water level would really be the issue. I'll look into the capacitor and thermal protection and try to change them to see if the issue persists. Thanks! – Adrian Lungu Jun 5 '17 at 21:12
  • It seems the problem was not the low water levels, but a bad thermal breaker. Bought a new one (although not the same brand as the original) and that one broke real quick. Ordered an original thermal breaker now and hopefully this one will work properly. Is it possible that bad wiring or the well pump is damaging the Thermal Protection in any way ? – Adrian Lungu Aug 14 '17 at 22:48
  • The good news is it was failing open that should have protected it from damage where if it failed closed I would expect damage if it was overheating.to see if the pump is the problem I would want to check the current draw to make sure the pump is running close to FLA (full load amperage). If you have the motor information it should provide the FLA or a close value can be looked up by voltage and horsepower. – Ed Beal Aug 14 '17 at 23:45
  • Last time I checked, the indicated current was somewhere around 0.2A. I'm not sure if that was an error on my part or my amp measurer was broken, or maybe it was 2A and I set the amp tool to the wrong scale. The max indicated in the pump specs is 6A. In any case, I assume if the pump was damaged, the breaker would trigger randomly. I'll check the amps tomorrow again just to be sure. – Adrian Lungu Aug 15 '17 at 0:06

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