Wiring for GFIs, only three wires

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  #1  
Old 04-01-11, 07:02 PM
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Wiring for GFIs, only three wires

I just bought a house and decided to double check all the plugs with a meter. Found four plugs that were reversed?
Anyway one of the bathrooms had a GFI plug installed but it came up as a reverse polarity.
When I opened it up there was only one white, one black and the ground.

How do I hook up to properly get protection.

Thanks
 
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Old 04-01-11, 07:50 PM
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When I opened it up there was only one white, one black and the ground.
That is all you need. Using a testlght or multimeter measure voltage between:
Ground and white
Ground and black.
Black and white

Post your results and we will go from there.
 
  #3  
Old 04-01-11, 09:02 PM
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If there are only 3 wires black white green. The green goes on the green ground screw. If the tester says polarity is reversed, just swap the black and white wires.
 
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Old 04-01-11, 09:31 PM
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People like to correct me on here when I give the simple functional solution so here is the extended code compliant version.

If the gfi has the black wire on the brass screw, white on silver and green on green, then it is wired correctly. You would then need to explore the other receptacles that might be feeding the gfi in question. Somewhere along the way you will most likely find a receptacle that has the blacks and whites mixed up on the same side of the receptacle. Correct that and the polarity will be correct as well as the color scheme of your wiring.
 
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Old 04-01-11, 10:11 PM
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Thanks Wire J,

The reason I even brought it up was that originally my gauge read that it was reversed and by looking at the wires it should have been reversed.
After reversing the wires the gauge still said it was reversed?

After checking the reat of the receptacles in the house they are all good now except this GFI.

Thanks,

WIS
 
  #6  
Old 04-02-11, 01:29 AM
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Maybe try moving the wires to another set of screws on the GFCI. Maybe someone put the line voltage wires on the Load side instead.If all the outlets on that circuit have black on brass white on silver maybe replace the GFCI.
 
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Old 04-02-11, 03:28 AM
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Let's start over. Do as Ray says and determine which wire is hot. Your bathroom should be wired by itself with no other room on that circuit. If you are getting a reversed polarity reading, it may be reversed in the breaker panel if the color code is correct at the GFCI. As stated don't just go swapping wires to achieve a correct meter reading. Do it right.
 
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Old 04-02-11, 06:07 AM
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Is it possible that there is already a tripped GFI in the circuit?
 
  #9  
Old 04-02-11, 02:11 PM
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Chandler what you said about the GFI being on its own circuit is fine if the house is new. If the house is older that code wasn't around and i've seen many houses with bathrooms, garages, front porch receptacles all on the same circuit and i've seen it in houses that were built as recently as the late 80s.

WIS, if the tester says its reversed polarity either way then perhapse the plug tester is faulty.

Take an actual multi meter and check voltage between the black and ground, the black and white, the white and ground. I dont know what voltage you have in canada but you should have voltage between black and white and black and green.

If you have voltage between white and green then the polarity really is reversed. If you have voltage between white and green and between the black and green but not between black and white, you may have a situation where both black and white are energized and need to be seperated.

 
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Old 04-02-11, 03:02 PM
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WJ, anything built after 1993 should have that code in effect, but you are correct some are not.
 
  #11  
Old 04-02-11, 08:30 PM
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Originally Posted by Wire Jockey View Post
I dont know what voltage you have in canada
Canada has the same voltage as the USA. 110/120 volts
 
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