Pool Heater trips the GFI circuit

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Old 01-03-11, 01:03 PM
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Pool Heater trips the GFI circuit

The GFI breaker recently tripped on the circuit leading to the filter and the pool heater. When I unplug the heater, the GFI does not trip. Both of these units have been running for years on this circuit so I know it is not a circuit overload. How can I determine whether the GFI breaker is breaking down or if it is a real ground fault that is happening? How can I test the heater to see if the problem exists within the heater or within the wiring leading to the outlet?
 
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Old 01-03-11, 01:17 PM
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How can I test the heater to see if the problem exists within the heater or within the wiring leading to the outlet?
Detach the wires at the heater and test. If the GFCI doesn't trip it is likely the heater. I'd replace the heater. You could Megger the heater but it might not show a problem that occurs when it is hot. GFCIs can wear out so it could also be the GFCI.
 
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Old 01-03-11, 01:24 PM
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Is this an electric heater or gas heater with electric ignitor?

The most basic test would be to open up the electric compartment in the heater and use a hair dryer to dry up any condensation and inspect for any leaking water into an electrical component.

A simple test is to measure resistance (ohms scale) with your multimeter between the hot and ground and between the neutral and ground in various components in the heater. This test should be done with the power supply disconnected. The resistance should measure infinity (zero on some meters), small faults will register as high numbers or intermittent zeros. This type of test will only detect certain types faults so it's not foolproof. A meter called a megger would be needed to do a more robust test, but use with care as a megger can damage some components.
 
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Old 01-03-11, 01:29 PM
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Thanks. I have used a Megger before to test for isolation between circuits, but not for ground fault tests. In the heater, what would I check with the Megger. Isolation between each power wire to ground or the heater chassis? What voltage setting would I use on the Megger? If I get some isolation resistance, what does it take to trip a GFCI?
 
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Old 01-03-11, 01:33 PM
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It is a gas fired heater. It draws little current. It has a blower motor, but does not pump gas nor water.
 
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Old 01-03-11, 01:42 PM
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An easier test would be to plug the heater into a different GFCI, and if it trips, it is the heater.
 
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