K8MHZ
Senior Member
- Occupation
- Electrician
Scenario:
Old two wire in workshop with concrete floor.
Mission:
Replace old two wire receptacle with new GFCI. Old receptacle in a metal 'handy box'.
Of course, I had to go find one of the new slim line types to even fit in the box. (I HATE it when people use handy boxes for receptacles!!)
So, I get done and my friend walks over to it with a plug in tester. I told him that his tester wouldn't work and that only the test button would as there was no ground wire.
Wrong!!!!
Not only did his tester show that there was a ground, but when he pushed the button on his tester, the GFCI tripped!
The only thing I can think of that provided a path to ground was the fact that the box was in a real rock plaster wall that went all the way to the floor. I could see the old NM in the box and it definitely was only two wire.
I just can't imagine that the plaster would be of low enough impedance to trick a tester into acting like there was a hard wired ground at the receptacle.
I just thought I would pass this along. Do not trust these testers 100 percent. (I don't trust ANY tester 100 percent, but that is just me!)
Old two wire in workshop with concrete floor.
Mission:
Replace old two wire receptacle with new GFCI. Old receptacle in a metal 'handy box'.
Of course, I had to go find one of the new slim line types to even fit in the box. (I HATE it when people use handy boxes for receptacles!!)
So, I get done and my friend walks over to it with a plug in tester. I told him that his tester wouldn't work and that only the test button would as there was no ground wire.
Wrong!!!!
Not only did his tester show that there was a ground, but when he pushed the button on his tester, the GFCI tripped!
The only thing I can think of that provided a path to ground was the fact that the box was in a real rock plaster wall that went all the way to the floor. I could see the old NM in the box and it definitely was only two wire.
I just can't imagine that the plaster would be of low enough impedance to trick a tester into acting like there was a hard wired ground at the receptacle.
I just thought I would pass this along. Do not trust these testers 100 percent. (I don't trust ANY tester 100 percent, but that is just me!)