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Thermistor - Tripping the pool GFI power safety device

March 28, 2019

Thermistor - Tripping the pool GFI power safety device

One item we get a lot of questions about is when a pool light is properly connected but constantly trips either the circuit breaker or the GFI device for pool lights.  When you encounter this situation there are typically only 2 scenarios that cause this. 

Scenario 1

In many pool lights there is a safety device that is built into the pool light called a thermistor.  This is a safety device, the way it works or is supposed to work is when a light bulb in the light over heats, it triggers the thermistor and the breaker or GFI trips.  Normally this require you to reset the breaker or GFI and go about your merry way.  In practice what actually occurs is the thermistor is physically damaged, melted in most cases and you will either get a light that works intermittently or not at all.  And what I mean by that is it constantly trips the breaker and/or GFI.

Unfortunately, when this occurs you have a light that would be better used as a door stop as it cannot be fixed.  

Scenario 2

This scenario is much more rare but it does happen and is very difficult to solve.  This scenario involves stray current over the ground connection.  Due to the complication of this scenario, I recommend you call us first as I couldn't possibly write down all of the ways this could be cause or fixed.  But I will say this, to test this scenario, all you have to do is disconnect the ground wire temporarily to see if the light works.  If the light that was tripping a circuit breaker or GFI stops tripping the breaker by disconnecting the ground wire, you have a stray current problem.  This is very serious and dangerous and requires much more work to resolve.  Please call us if this occurs.

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