Only one room testing as Not Grounded?

brad34 · 07-15-2012, 06:55 PM

Another question already...

I have a house built in 1966. All of the outlets upstairs have metal boxes with no visible ground wire. A receptacle tester shows all of the outlets as grounded except for the living room.

So I'm wondering, what might the reason be for the living room not testing as grounded? When I touch a "pig-tail" tester to the hot wire and directly to the box, it lights up, so perhaps the ground is too weak for the receptacle tester to detect it? The outlets in the other rooms are the same as the ones in the living room, so I'm confused as to what is making the difference.

I know there are numerous possibilities here, but I'd like to hear your theories on what may be going on.

stickboy1375 · 07-15-2012, 07:39 PM

Quote:

Originally Posted by brad34

Another question already...

I have a house built in 1966. All of the outlets upstairs have metal boxes with no visible ground wire. A receptacle tester shows all of the outlets as grounded except for the living room.

So I'm wondering, what might the reason be for the living room not testing as grounded? When I touch a "pig-tail" tester to the hot wire and directly to the box, it lights up, so perhaps the ground is too weak for the receptacle tester to detect it? The outlets in the other rooms are the same as the ones in the living room, so I'm confused as to what is making the difference.

I know there are numerous possibilities here, but I'd like to hear your theories on what may be going on.

First off, what wiring method is installed? Most likely, somewhere along the way, you have a junction box that contains shoddy connections.

brad34 · 07-15-2012, 08:29 PM

Quote:

Originally Posted by stickboy1375

First off, what wiring method is installed? Most likely, somewhere along the way, you have a junction box that contains shoddy connections.

Type TW..it looks like the first floor is through conduit.

stickboy1375 · 07-15-2012, 08:49 PM

Quote:

Originally Posted by brad34

Type TW..it looks like the first floor is through conduit.

If its old AC wiring and it doesn't contain a bonding strip within, then all you can do is GFCI protect the circuit install grounded receptacles....

Yoyizit · 07-16-2012, 01:39 PM

Quote:

Originally Posted by brad34

so perhaps the ground is too weak for the receptacle tester to detect it?

Yes, a high resistance ground, maybe due to rust.
More than 1/2 ohm between your neutral and ground terminals measured at the outlet is probably too much.

If you buy a real multimeter it'll pay for itself the first time you use it to correctly diagnose a problem.

jrclen · 07-16-2012, 03:50 PM

Maybe a conduit connection is corroded or no longer connected in that room.