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JLMCDANIEL
Re: Open Ground

Probably nothing if your using it for appliances with 2 pronged plugs. If you use it for electronic equipment with a 3 prong plug the filtering and safety protection won't work. If you plus a tool with a 3 prong plug into it and the hot wire is shorted to the case you could get electrocuted.
Jack

Re: Open Ground

In my opinion a ground is probably the most important wire in a modern wiring installation. A ground is used to carry a fault current back to the main service and draw maximum current which then causes the circuit breaker to trip or fuse to open. That being said the fault must be directed to the ground by either a three prong male plug in the appliance cord. That ground wire must be grounded to the metal frame of the appliance and or electrical device ground path. But as Jack Stated if there is only a two prong cord it is not used.
Having a three prong outlet that has no ground is giving a false indication that a ground is present. It typically is a easy fix I would suggest you take time and pull the outlet and check.

Turn off the power and see if there is a bare or green wire attached to the outlet. if it is check to make sure it is connected to the other ground wires and tight.

If that does not fix your problem come on back and we will help.:)

canuk
Re: Open Ground

Yep .... great post Ravens53. ;)

tmas
Re: Open Ground
Ravens53 wrote:

In my opinion a ground is probably the most important wire in a modern wiring installation. A ground is used to carry a fault current back to the main service and draw maximum current which then causes the circuit breaker to trip or fuse to open. That being said the fault must be directed to the ground by either a three prong male plug in the appliance cord. That ground wire must be grounded to the metal frame of the appliance and or electrical device ground path. But as Jack Stated if there is only a two prong cord it is not used.
Having a three prong outlet that has no ground is giving a false indication that a ground is present. It typically is a easy fix I would suggest you take time and pull the outlet and check.

Turn off the power and see if there is a bare or green wire attached to the outlet. if it is check to make sure it is connected to the other ground wires and tight.

If that does not fix your problem come on back and we will help.:)

No third wire. I thought that the box was ground (used a volt meter with a prong in the hot and the other on the plate screw), but when I replaced the 2-prong with a 3-prong it wasn't grounded. Actually, it was grounded the first time I checked it, but when I changed a second outlet on the same breaker and the check that one with a 3-prong, 3-light checker it blow the middle light of the checker out and ungrounded the other circuit. Weird.

Thanks for you help.

canuk
Re: Open Ground
Quote:

No third wire. I thought that the box was ground (used a volt meter with a prong in the hot and the other on the plate screw), but when I replaced the 2-prong with a 3-prong it wasn't grounded.

There is definately something suspicious here.

If you originally have 2 slot receptacle you wouldn't have a ground.

What type of wiring do you have .... is it a cloth type covering on the 2 conductor cable or is is a flexable metal cover over the 2 conductors (BX) ?

Is there a bare copper ground wire from the breaker panel to a ground rod or to the main water supply pipe where it enters to home?

Are there series of wires running from the boxes to a water pipe running through the house?

tmas
Re: Open Ground
canuk wrote:

There is definately something suspicious here.

If you originally have 2 slot receptacle you wouldn't have a ground.

What type of wiring do you have .... is it a cloth type covering on the 2 conductor cable or is is a flexable metal cover over the 2 conductors (BX) ?

Is there a bare copper ground wire from the breaker panel to a ground rod or to the main water supply pipe where it enters to home?

Are there series of wires running from the boxes to a water pipe running through the house?

It looks like I have both 2 cloth covered and flexable metal wires depending on the outler. The main breaker box has been replaced and is ground via a copper cable to the water main.

canuk
Re: Open Ground
Quote:

I have both 2 cloth covered and flexable metal wires depending on the outler

That might explain why you were seeing an apparent ground on the plate screw on some outlets and not on others. The BX type metal case cable at some outlets would be showing the apparent ground and the cloth covered cables attached to the other outlets wouldn't show any ground.

Quote:

3-light checker it blow the middle light of the checker out and ungrounded the other circuit. Weird.

Did this also trip the breaker?

tmas
Re: Open Ground
canuk wrote:

That might explain why you were seeing an apparent ground on the plate screw on some outlets and not on others. The BX type metal case cable at some outlets would be showing the apparent ground and the cloth covered cables attached to the other outlets wouldn't show any ground.

Did this also trip the breaker?

It didn't trip the breaker, just blew the middle light of the three-light tester.

So were those boxes grounded or was it just a false reading?

canuk
Re: Open Ground
tmas wrote:

It didn't trip the breaker, just blew the middle light of the three-light tester.

So were those boxes grounded or was it just a false reading?

The testers typically use Neon bulbs ... can't say why it "blew" if it did.

If those BX type cables run from the fixture box back to the service panel check the metal cable jacket for continuity to ground. There are likely metal cable strains that secure the cable to the metal service panel case and the fixture box for the receptacle. This would show the apparent ground at the receptacle .... this is an unreliable and inappropriate method to use as a grounding system for the receptacle.

Sounds as though there is something strange going on and it may be in your best interest to have an electrician check things out ..... otherwise just guessing here.

Master Electrician
Re: Open Ground

BX cable has a metal wound casing, and this casing has a high resistance over the length of the cable. If this casing is used as a grounding conductor, and a fault should occur, this casing will heat up and glow like a toaster element, resulting in a fire. Unlike MC cable, which has a grounding conductor running the full lenth of the cable and is rated for the fault current. I have personally wittnessed this on a service upgrade I was doing and about bit my scritches.:eek: So please, don't use the BX sheath for a grounding conductor unless you know what you are doing. One of the fixes in this instance that is approved by code, is to intall a GFCI rec.

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