What happens with an incorrectly wired GFCI

Just a li'l anecdote for those who've always wondered what happens if you wire a GFCI to protect "downstream" outlets wrong (all 2 of you)--that is, if you mix up the "line" and "load" wires.
The answer? Nothing.
Installed a GFCI in a client's kitchen, thinking I'd need two, one for each outlet on a sink counter. It became clear, though, that they were in a chain, so I could protect both with just one GFCI. So I wired in the GFCI, wiring the downstream outlet on the "load" side, ass-u-ming that the position of the cables in the box indicated the upstream and downstream wiring respectively.
Wrong.
When I turned on the power, the GFCI's LED lit, but I couldn't reset the outlet, and both outlets were dead.
Whoops.
So I swapped the two sets of wires, repowered it, reset the GFCI and bingo! everything worked fine.
The moral of the story is, you won't damage a GFCI by making this mistake (but you'd better correct it if you want the devices to work correctly).
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wrote:

Strange, when I made the same mistake the outlets worked normally but wouldn't trip on a "downstream" fault. The differential current sensing was on the wrong side of the device, so didn't detect the fault. I can't see how they'd fail the way you suggest.

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( snipped-for-privacy@att.bizzzzzzzzzzzz) writes:
| wrote: | | >Just a li'l anecdote for those who've always wondered what happens if | >you wire a GFCI to protect "downstream" outlets wrong (all 2 of | >you)--that is, if you mix up the "line" and "load" wires. | > | >The answer? Nothing. | > | >Installed a GFCI in a client's kitchen, thinking I'd need two, one for | >each outlet on a sink counter. It became clear, though, that they were | >in a chain, so I could protect both with just one GFCI. So I wired in | >the GFCI, wiring the downstream outlet on the "load" side, ass-u-ming | >that the position of the cables in the box indicated the upstream and | >downstream wiring respectively. | > | >Wrong. | > | >When I turned on the power, the GFCI's LED lit, but I couldn't reset the | >outlet, and both outlets were dead. | | Strange, when I made the same mistake the outlets worked normally but wouldn't | trip on a "downstream" fault. The differential current sensing was on the | wrong side of the device, so didn't detect the fault. I can't see how they'd | fail the way you suggest.
Newer GFCIs are specifically designed to be idiot-proof in this respect. They aren't failing; they are just helping you. :) Although older GFCIs would not be damaged by the incorrect wiring, they wouldn't be able to shut off the power to the local outlet even if they trip.
                Dan Lanciani                 ddl@danlan.*com
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Dan Lanciani wrote:

Does that mean OP was an idiot?
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On 3/12/2011 3:36 PM Tony Hwang spake thus:

No, it means I *made a mistake* and was "helped" by the GFCI not being damaged by it.
Are you an idiot? Sometimes you sound like one ...
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But how does that work? How does the GFCI know which side is line and load?

No, he got proofed immediately. I had to wait for an inspector (selling the house) to get proofed. ;-)
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( snipped-for-privacy@att.bizzzzzzzzzzzz) writes:
| | > | > | >Dan Lanciani wrote:
snipped-for-privacy@att.bizzzzzzzzzzzz ( snipped-for-privacy@att.bizzzzzzzzzzzz) writes: | >> | On Sat, 12 Mar 2011 13:52:58 -0800, David
| >> | wrote: | >> | | >> |>Just a li'l anecdote for those who've always wondered what happens if | >> |>you wire a GFCI to protect "downstream" outlets wrong (all 2 of | >> |>you)--that is, if you mix up the "line" and "load" wires. | >> |> | >> |>The answer? Nothing. | >> |> | >> |>Installed a GFCI in a client's kitchen, thinking I'd need two, one for | >> |>each outlet on a sink counter. It became clear, though, that they were | >> |>in a chain, so I could protect both with just one GFCI. So I wired in | >> |>the GFCI, wiring the downstream outlet on the "load" side, ass-u-ming | >> |>that the position of the cables in the box indicated the upstream and | >> |>downstream wiring respectively. | >> |> | >> |>Wrong. | >> |> | >> |>When I turned on the power, the GFCI's LED lit, but I couldn't reset the | >> |>outlet, and both outlets were dead. | >> | | >> | Strange, when I made the same mistake the outlets worked normally but wouldn't | >> | trip on a "downstream" fault. The differential current sensing was on the | >> | wrong side of the device, so didn't detect the fault. I can't see how they'd | >> | fail the way you suggest. | >> | >> Newer GFCIs are specifically designed to be idiot-proof in this respect. | >> They aren't failing; they are just helping you. :) Although older GFCIs | >> would not be damaged by the incorrect wiring, they wouldn't be able to | >> shut off the power to the local outlet even if they trip. | | But how does that work? How does the GFCI know which side is line and load?
I don't know if they all work the same way, but the ones I have looked at are pretty simple. They start in the tripped state. The reset button is no longer a simple mechanical device; it is interlocked such that the device cannot be reset unless there is power on the line side. You can probably defeat the protection by installing correctly (or on a bench), pushing reset, installing incorrectly, and then never pushing the test button. But who would do that? :)
                Dan Lanciani                 ddl@danlan.*com
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On 3/12/2011 7:57 PM, Dan Lanciani wrote:

Dan, did you see my post titled: "OT, Do You Know Anyone Like This"? ^_^
TDD
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On 13 Mar 2011 01:57:15 GMT, ddl@danlan.*com (Dan Lanciani) wrote:

That works. Ingenious, even. Thanks.
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Dan Lanciani wrote:

I agree.
Older GFCIs had the load terminals connected to the receptacle. If connected line-load reversed the receptacle was always powered and a ground fault on the receptacle would not trip the GFCI. The test button would trip the GFCI but the outlet was still hot. Anything connected downstream would be protected as intended. Instructions are likely to say to connect a lamp and push the test button - make sure the lamp goes out.
A while ago the UL standards changed. Now if a GFCI trips, the receptacle is not connected to the line or load terminals. The internal electronics are probably connected to the receptacle. If these GFCI receptacles are "set" and installed with line-load reversed they shouldn't detect a ground fault on the receptacle. Downstream protects as intended. If you push the test button the GFCI trips and can not be reset. They are intentionally shipped in the tripped condition, so if a new GFCI is installed line-load reversed it can not be reset.
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Thanks for the info. I had a GFCI that worked but the reset was popped out and wouldn't stay in. The three sockets downstream didn't work. Sure enough to the load and line were switched. I switched them back and everything wo rks! Glad it was such a simple fix.
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