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Electrical Ground Problem

6K views 15 replies 6 participants last post by  cabinetman 
#1 ·
We ordered U-verse, and one of the requirements is that the outlets must be grounded. One of the outlets tested "open ground". The outlet is screwed to a metal box, inside an interior block wall. I'm pretty sure there's conduit.

I added a ground wire to the outlet and screwed it to the box, still tests "open ground". Any suggestions?






 
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#5 ·
I can't tell if there is a break in the conduit. The house was built in the 50's. This outlet is in the original part of the house. The house was doubled in size about 15 years later, and the original (glass) fuse type box remains, but was wired into a 200 A panel on the new addition. There may be a loose ground that didn't make it to the panel.

I would hate to have to call an electrician to pull a ground just for this TV installation. I called AT&T and was told that a battery back up/surge protector would suffice even if the duplex showed an "open ground".

I don't want to spend the bucks for one of those to get by, and have the installation tech tell me it isn't aqcceptable.






 
#7 · (Edited)
Over time, oxidation occurs on the surfaces of conduit. If the parts were not firmly fastened together, they might no longer form a continuous path from the outlet box in question back to the panel.

It is a good idea to retorque (retighten) the screws and setscrews that hold the wires in the panel every 10 years or so, but it is impractical to retorque the screws that hold the conduit components in place as the latter may be inside the walls.

It is permissible to ground electronic equipment by daisy chaining a bare wire from one piece of equipment to another, fastening the wire with a screw or bolt that goes through to the chassis. Connect the free end to a known ground, which could be a water pipe that is known to be metal all the way down to the basement and out to the water main, or all metal down to a clamp where another ground wire goes to the panel. Or this ground wire can go along the baseboards and up and over doorways and down to the panel.

The "insulating" washers on the yokes of receptacles etc. are there to keep the included screws from falling out and getting lost in the store or warehouse bins. An alternative to a ground wire or pigtail in a metal box is to substitute a special grounding clip for one of those cardboard washers. Simply removing the washers does not make for a proper bond to a metal box although the contact is as good as a pigtail attached to the edge of the box using another kind of grounding clip.
 
#9 ·
It is permissible to ground electronic equipment by daisy chaining a bare wire from one piece of equipment to another, fastening the wire with a screw or bolt that goes through to the chassis. Connect the free end to a known ground, which could be a water pipe that is known to be metal all the way down to the basement and out to the water main, or all metal down to a clamp where another ground wire goes to the panel. Or this ground wire can go along the baseboards and up and over doorways and down to the panel.

Thanks for the reply. I realize that pulling a ground wire would be the best method. Short of that, since the outlet is behind a cabinet and one side of the cabinet is against an outside wall, how about a primary ground. What I'm thinking is to drive a copper pipe into the ground, and run a wire (surface mount to the outlet), and drilling through the wall and into the box. If I did that, first, would that work, and second, what diameter of copper pipe, and how deep does it have to go?

I also have the main outdoor spigot about 40' from that wall location that I could tie to.






 
#12 ·
Then you still need the low impedance path not a high resistance one. The purpose may not be for human protection as far as what Uverse wants but I'm not sure how much "extraneous" current if any will flow to strictly an earth ground at the voltage it will be at. Considering if the receptacle was a typical grounding one and properly grounded to the electrical system ..how much of that extraneous current would go to earth? Considering it has a low impedance path available to it. IMO what they want is a connection to a 'proper' electrical ground so that low impedance path is available to the 'extraneous current'.
 
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