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· Registered
35 Posts
Discussion Starter · #1 ·
A friend called and asked for help with the in floor heat.
The thermostat has a built in GFI.
The GFI trips when he turns on the system.
The heat cables so no resistance to ground. There is resistance between the two, but I can't remember how much, maybe 60 ohms.
He tried another thermostat and it still tripped the GFI.

Any thoughts on what else to check?
Will the temp sensor trip the GFI?

· Electrical Contractor
1,995 Posts
What was the resistance readings ground to neutral and ground to hot?

Should be no reading between hot to ground or neutral to ground. Just like when you have the leads not touching anything.

Sounds like a problem with the heating cable.

· Registered
32 Posts
Most likely a damaged cable that is causing a short between one of the power
leads and the grounded sheath. The only solution is to find the damaged section
and install a splice kit. This often means the entire cable needs to be taken up
and replaced.

A defective GFCI is another, not too likely, possibility. Testing with a known
good GFCI will reveal if this is the case.

The temperature sensor is not directly connected to the power wiring, so should
not cause the GFCI trip, but can be easily tested by disconnecting the sensor
wire from the thermostat.
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