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Old 02-09-2008, 11:32 PM   #1 (permalink)
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Block heater trips GFCI

The block heater on my 2005 LLY trips ground fault circuit interrupter outlets when plugged into them, but does not trip the circuit breaker on a conventional outlet. I measured the resistance at about 500,000 ohms from both hot to ground and neutral to ground. Anyone else have this problem?

2005 Chev XC K3500 SRW 4x4 D/A
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Old 02-10-2008, 12:48 AM   #2 (permalink)
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I think your GFCI simply can't handle the load. Use a non-GFCI outlet.
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Old 02-10-2008, 12:49 AM   #3 (permalink)
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Very small amp draw on those gfci's, use non- gfci
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Old 02-10-2008, 12:58 AM   #4 (permalink)
Rob from BC Canada
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Mine does it too,

For some time, I was thinking the block heater wasn't working, it never seemed to warm up.

Glad to hear its not just mine, but I wonder why. I regularly run a 1500 watt fan heater in my camper on the same GFCI outlet, and that doesn't kick it.

It is hooked to a thermostat, so it comes on whenever it gets cold in there. That is about 13 amps at 115 volts.

There must be some other reason.
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Old 02-10-2008, 02:40 AM   #5 (permalink)
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how old is the outlet? could be going bad....oversensitive.
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Old 02-10-2008, 03:05 AM   #6 (permalink)
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I don't plug my truck up, but my CAT end loader at work is plugged up in a gfci and never trips it.
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Old 02-10-2008, 11:32 AM   #7 (permalink)
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my block heater is also plugged into a gfci outlet- no problems here.
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Old 02-10-2008, 11:48 AM   #8 (permalink)
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Same here, I plug mine in at work during the day and it is a GFCI Outlet. I have clamped an amprobe on while it was running and it only pulls anout 7.5 A I would guess you have something wrong if the GFCI is tripping.

A GFCI Senses voltage return on the neultral side of the load and if there is an imbalance detected it will trip the GFI most of them are set at 3-5 mA to trip.
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Old 02-10-2008, 11:50 AM   #9 (permalink)
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How 'bout a bad extension cord? Maybe try a different one...
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Old 02-10-2008, 12:03 PM   #10 (permalink)
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Originally Posted by jollyrogr View Post
I think your GFCI simply can't handle the load. Use a non-GFCI outlet.
The GFI will not trip on an over-current, it's not a circuit breaker.
My defective cord would trip a GFI with 200K ohms Hot or Neutral to Grd.
The GFI is probably working, and your heater cord probably has issues.

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