Jump to content

GFCI on two wire system


Focal Point
 Share

Recommended Posts

I have an Ideal GFI / AFI tester.

If I test a GFI that is installed on an older 2 wire system, it will not trip.

After speaking with an electrician about this he says the outlet is still protected, however the tester won't trip the breaker because of the neutral. So...

Would the GFCI trip if I placed a ground lift adapter on it?

Link to comment
Share on other sites

Originally posted by Focal Point

I have an Ideal GFI / AFI tester.

If I test a GFI that is installed on an older 2 wire system, it will not trip.

After speaking with an electrician about this he says the outlet is still protected, however the tester won't trip the breaker because of the neutral. So...

Your tester works by shunting a small amount of current to the ground prong. If the receptacle is ungrounded, the shunt achieves nothing and the GFCI doesn't trip.

When you run into a GFCI on an old two-wire system, use the test button on the GFCI device itself then use your tester to ensure that the power to the outlet has actually been cut.

The GFCI's internal tester uses a small resistor to create an imbalance in the line that mimics a ground fault. It's a perfectly valid test.

Would the GFCI trip if I placed a ground lift adapter on it?

I don't know what a ground lift adapter is. ??

- Jim Katen, Oregon

Link to comment
Share on other sites

A ground lift adapter is the thing that is used to insert a three prong plug into a two prong receptacle. cinemasupplies_1907_5215722

http://cinemasupplies.stores.yahoo.net/grliadco41.html

I haven't tried using the adapter on a plug-in GFI tester, but I would expect that you still couldn't get your plug-in tester to trip the GFI unless you took the time to connect the grounding tab to a good ground.

The best thing to do is to perform the test as Jim described -- by using the test button on the GFI receptacle and then use the tester to confirm that the power has been interrupted. The test button on the GFI receptacle (or breaker) mimics the condition that the GFI device is monitoring, while the plug-in tester creates an alternative condition which causes the GFI to trip under most (but not all) circumstances.

Brandon

Link to comment
Share on other sites

Ok, but here's my problem when I plug it in and press the button, the tester reads open ground and nothing happens. However the electrician swears it's protected.

I got the idea from a picture of some inspector with the adaptor on his tester. Thats the only possible reason I could come up with.

P.S Ground lift adapters are every professional soundman's best friend...I have been doing sound for around 15 years and they are great for removing annoying hums from your mix.

Link to comment
Share on other sites

That's because you have an open ground and without a ground a tester that uses a GFCI test button can't create the ground fault needed to trip the device. The electricians right. You don't need a ground for a ground fault circuit interrupter to trip - it will trip with or without an equipment grounding conductor connected. You aren't checking the ground, you're detecting a ground fault. Two different things. Use the test button on the receptacle on 2-wire systems to check the GFCI's and only use your tester to verify proper polarity. That's as far as you need to go.

ONE TEAM - ONE FIGHT!!!

Mike

ONE TEAM - ONE FIGHT!!!

Mike

Link to comment
Share on other sites

Originally posted by Focal Point

Ok, but here's my problem when I plug it in and press the button, the tester reads open ground and nothing happens. However the electrician swears it's protected.

Well, yeah, of course nothing happens. The tester isn't creating a ground fault, so the GFCI isn't tripping.

If you were to use one of your ground lift adapters, screwing the green ring to the coverplate screw, it might work -- IF the outlet box were grounded. If the outlet box isn't grounded, the ground lift adapter won't do squat.

Once again. For your handheld tester to work, it must have access to a good ground through which it can shunt some juice. Without a good ground, the tester won't tell you whether or not the GFCI is working. But the GFCI's built-in test button will always work.

I got the idea from a picture of some inspector with the adaptor on his tester. Thats the only possible reason I could come up with.

In my area, there was a period of time from the mid '50s to the mid '60s where they ran grounded romex cables and attached the grounding wires to the outlet boxes but still installed 2-slot receptacles. In these houses, your adapter would achieve what you're seeking -- but you'd have to attach the grounding connection.

P.S Ground lift adapters are every professional soundman's best friend...I have been doing sound for around 15 years and they are great for removing annoying hums from your mix.

Probably for the same reason I explained above. But on a truly ungrounded system, they'll achieve nothing.

- Jim Katen

Link to comment
Share on other sites

David,

Mike is right on about the book it's a must have and read for all inspectors.

I would not try to alter the plug on the Ideal Sure Test, they've had problems with the plugs and cords, may adversely or inaccurately affect test or tester.

If you just have to experiment I would advise against it and contacting them to see what their warranty policy would be if negative results occurred to your equipment.

The test/reset buttons are the surest way to test GFCI and AFCI if these work/terminate power you will have a hard time convincing any electrician or homeowner that the receptacle or breaker is in some way defective and needs to be replaced.

Link to comment
Share on other sites

  • 2 weeks later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...