Thread: Common neutral and ground connection?

I was inspecting an 1840 antique colonial last weekend and noticed that there was a lot of BX cable and ungrounded romex used for distribution wiring.

Most of the outlets in the house were grounding 3-prong type, so I expected to find plenty of ungrounded outlets (changeovers from 2 - 3 prong). To my surprise -- When I started testing the outlets with my $10.00 gfci/polarity tester they all seemed OK.

As I was finishing in the attic I found the reason they all tested good.

I guess I need a better type testing device. Would your expensive fluke testers have picked that up???

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I have heard the suretest will flag a low resistance between ground and neutral as a "bootleg" or "false" ground.

The issue you found would be higher/normal resistance readings and would fool the ole suretest.

Originally Posted by Ken Amelin

I was inspecting an 1840 antique colonial last weekend and noticed that there was a lot of BX cable and ungrounded romex used for distribution wiring.

Most of the outlets in the house were grounding 3-prong type, so I expected to find plenty of ungrounded outlets (changeovers from 2 - 3 prong). To my surprise -- When I started testing the outlets with my $10.00 gfci/polarity tester they all seemed OK.

As I was finishing in the attic I found the reason they all tested good.

I guess I need a better type testing device. Would your expensive fluke testers have picked that up???

I don't see why that in itself would explain the tester indicating properly grounded 3-prongs. There still has to be conductor attached to the grounding connection on the receptacles that either is boot-legged to the neutral connection, or is connected to the armored cable, for instance.
Not to discount what you found, of course. There is now neutral current on the outside of the armored cable, assuming that is the neutral.

Originally Posted by John Arnold

I don't see why that in itself would explain the tester indicating properly grounded 3-prongs. There still has to be conductor attached to the grounding connection on the receptacles that either is boot-legged to the neutral connection, or is connected to the armored cable, for instance.

He more than likely has all metal boxes and the receptacle mounting screws are providing the "ground"...don't need an actual wire to the terminal. Oh...and I agree the Suretest wouldn't pick that up, proving that Ken's brain is still the best piece of equipment he has!