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cabinetman 01-27-2010 03:15 PM

Electrical Ground Problem
 
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?







wirenut1110 01-27-2010 03:56 PM

Hook the ground to the receptacle.

If you hooked it to the box then the insulating washers on the receptacle that hold the screws will keep it from making contact.

cabinetman 01-27-2010 04:05 PM

Quote:

Originally Posted by wirenut1110 (Post 390135)
Hook the ground to the receptacle.

If you hooked it to the box then the insulating washers on the receptacle that hold the screws will keep it from making contact.


Thanks for the reply. It's a 2 wire 12ga, no ground wire. I attached a ground wire from the receptacle (green screw) to the box. There are no insulating washers on anything. Still tests "open ground".







wirenut1110 01-27-2010 04:13 PM

Does conduit run the whole way? Is it broken somewhere?

If it's just stubbed up in the block and poking out under the house or something, I don't see a big deal with using a bonding bushing on the end of the pipe and grounding it like that.

cabinetman 01-27-2010 04:37 PM

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.







hayewe farm 01-27-2010 10:56 PM

At&T is full of crap. A battery back up/surge protector does not replace the requirements for a ground in fact most battery back up/surge protectors need a ground to function properly.

AllanJ 01-28-2010 08:28 AM

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.

cabinetman 01-28-2010 11:54 AM

Quote:

Originally Posted by hayewe farm (Post 390342)
At&T is full of crap. A battery back up/surge protector does not replace the requirements for a ground in fact most battery back up/surge protectors need a ground to function properly.


Thanks. That's what I'm thinking too (about AT&T, and the ground).







cabinetman 01-28-2010 11:55 AM

Quote:

Originally Posted by AllanJ (Post 390464)

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.







Stubbie 01-28-2010 12:31 PM

1 Attachment(s)
Quote:

Originally Posted by cabinetman (Post 390138)
Thanks for the reply. It's a 2 wire 12ga, no ground wire. I attached a ground wire from the receptacle (green screw) to the box. There are no insulating washers on anything. Still tests "open ground".







Unfortunately you are one of many whom do not understand the purpose of the equipment ground vs ground rods and the grounding electrode system. Equipment ground as you are dealing with is for human safety from electrocution. Ground rods and other electrodes are for lightning protection and utility power surges to protect the electical system from damage. The equipment ground is a low impedance back to the center tap of the utility transformer not to earth. This is so enough current will flow to the transformer and consequently through the circuit breaker to open it in the event of a ground fault to a hot conductor.

Running a single wire for equipment ground out to a ground rod will do nothing to provide for opening the circuit breaker as the fault path to earth is such a high resistance it will only let 5 or 6 amps flow on a fault and no breaker will open.

Anyway your not totally out of luck. You do have some options to get the receptacle grounded as it seems you do not have a good ground of anykind for that receptacle. My guess is the nm 12/2 (no ground) is just run in sleeve of conduit for protection

Here is what you are allowed since UVerse wants the outlet to have equipment ground. but I qusetion if it is necessary. Grounding the outlet though will increase your safety from shock.

You can route a single wire for equipment ground from the receptacle to any point on your metal cold water pipe as long as the connection point is not further than 5 feet from where it enters your house and that water pipe is also being used as a grounding electrode. Meaning it has a big copper wire connected to it from the electrical panel neutral bar. This provides the low impedance path back to the transformer. Or you can connect to any grounding electrode conductor that is ran from your service panel to water pipes or ground rods or other electrodes. These are the green lines you see in the drawing below going to the water pipe and ground rod. You must use a listed connector not hose clamps or stuff like that. You can also run the ground to the electrical panel itself.

Make sense?

For your fyi this drawing below shows the low impedance fault path needed for equipment ground notice that earth is not part of that path. Some current does flow to earth but it is insignificant as long as the "effective ground fault path" is properly constructed.

hayewe farm 01-28-2010 12:59 PM

Stubbie,
Your information is good however electronic equipment with noise filtering needs a path to earth ground. This is not a fault path but a path to run extraneous current..

Stubbie 01-28-2010 01:42 PM

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'.

cabinetman 01-28-2010 04:06 PM

Quote:

Originally Posted by Stubbie (Post 390585)
You can route a single wire for equipment ground from the receptacle to any point on your metal cold water pipe as long as the connection point is not further than 5 feet from where it enters your house and that water pipe is also being used as a grounding electrode.


Thanks for the help. This might be my easiest out. I would just like the duplex to show a ground instead of "open ground". What would connecting the ground (green screw) to the neutral wire do?




jbfan 01-28-2010 04:35 PM

Quote:

Originally Posted by cabinetman (Post 390706)
Thanks for the help. This might be my easiest out. I would just like the duplex to show a ground instead of "open ground". What would connecting the ground (green screw) to the neutral wire do?




Created a bootleg ground, violate the NEC, and could become a hazard later on!

Stubbie 01-28-2010 04:52 PM

Quote:

Originally Posted by cabinetman (Post 390706)
Thanks for the help. This might be my easiest out. I would just like the duplex to show a ground instead of "open ground". What would connecting the ground (green screw) to the neutral wire do?




As Jbfan said this is called a bootleg ground and is a common thing homeowners do to fool house inspectors when they stick their receptacle testers into the receptacle to check for proper wiring. And some think because the ground and neutral go to the same place in the service equipment panel it does the same thing as having a ground.
However this is not the case. The reason is ... the neutral is a current carrying wire just like the hot wire. It is the wire on the load side of your appliances, lights. etc... that completes the electrical circuit to the main panel and utility transformer. It carries the same current your hot wire does and it can electrocute you given the right circumstances. In contrast the ground wire is a non -current carrying wire and only has current on it briefly till the circuit breaker opens if a fault occurs. No ground fault then no current is ever to be flowing on the ground wire .. especially neutral current.
By connecting the two at a receptacle you give the neutral current an alternate path to take. If you plug something into the receptacle the neutral current will travel up the ground in the power cord and energize the metal case of the appliance your operating. Where this becomes deadly is if the neutral wire opens somewhere. Neutral current now has an alternate path due to the bootleg. It really can't go anywhere till a person comes along and provides that complete circuit.
So no .. don't ever connect the ground and neutral together it is not safe by a long shot.


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