Panel ground questions

Joe F · 08-04-2008, 02:08 PM

I recently did some plumbing work and needed to lengthen the ground wire that goes to the copper plumbing main. The existing ground is 4ga and I added 3 feet of 6ga spliced in with 2 bugs. Do I need to swap it out with a piece of #4 or am I OK as is?

While I was doing this work I started thinking

. Aren't the neutral and ground the same where they attach to the earth ground (copper pipe or driven ground)? If they are the same, why isn't there current in the ground wire? or is there? I couldn't figure this out when I was doing the work so I killed the main until I had the ground re-bonded to the plumbing line.

chris75 · 08-04-2008, 04:17 PM

Quote:

Originally Posted by Joe F

I recently did some plumbing work and needed to lengthen the ground wire that goes to the copper plumbing main. The existing ground is 4ga and I added 3 feet of 6ga spliced in with 2 bugs. Do I need to swap it out with a piece of #4 or am I OK as is?

If your copper pipe is a GEC (grounding electrode conductor) then you cant splice it, back to the drawing board.

Quote:

Originally Posted by Joe F

While I was doing this work I started thinking

. Aren't the neutral and ground the same where they attach to the earth ground (copper pipe or driven ground)? If they are the same, why isn't there current in the ground wire? or is there? I couldn't figure this out when I was doing the work so I killed the main until I had the ground re-bonded to the plumbing line.

Because the current wants to get back to the transformer on the street not to the earth. Ground rods and using the metal piping as a grounding electrode are only for lightning, surges, unintentional contact with higher-voltage lines.

Joe F · 08-04-2008, 04:30 PM

Quote:

Originally Posted by chris75

If your copper pipe is a GEC (grounding electrode conductor) then you cant splice it, back to the drawing board.

OK. I'll run a new ground wire back to the panel. What size wire do I need for a 200 amp service?

Stubbie · 08-04-2008, 04:31 PM

Turning the main off will not remove dangerous amperage on the grounding conductors if it is coming from an external source due to a fault on the utilities grid such as a neighbors service lateral. treating the grounding conductor like any other is a good idea never assume it is safe to handle before testing for current flow. There are many plumbers who will attest to the current flow in metal drain pipes....from external faults outside the home....

chris75 · 08-04-2008, 06:13 PM

Quote:

Originally Posted by Joe F

OK. I'll run a new ground wire back to the panel. What size wire do I need for a 200 amp service?

Its actually based on the size of the service entrance conductors, but most likely #4 cu. is good.

chris75 · 08-04-2008, 06:14 PM

Quote:

Originally Posted by Stubbie

Turning the main off will not remove dangerous amperage on the grounding conductors if it is coming from an external source due to a fault on the utilities grid such as a neighbors service lateral. treating the grounding conductor like any other is a good idea never assume it is safe to handle before testing for current flow. There are many plumbers who will attest to the current flow in metal drain pipes....from external faults outside the home....

And here is a great article to explain all about it... http://ecmweb.com/grounding/electric...uth_grounding/

Yoyizit · 08-04-2008, 06:49 PM

"Because the current wants to get back to the transformer on the street not to the earth."

This may have already been said or implied, but the voltage to ground of an ungrounded xformer secondary is indeterminate.
Because of interwinding parasitic capacitance, the secondary voltage may float up to the primary voltage, or it may not because winding capacitance to ground may overwhelm the other capacitances.
Grounding the center tap somewhere makes the secondary voltage with respect to ground predictable and independent of stray capacitance; that is, a max of 150vrms.

Mr. 75, there is more to that article than meets the eye. It may save lives.

chris75 · 08-04-2008, 08:21 PM

Quote:

Originally Posted by Yoyizit

"Because the current wants to get back to the transformer on the street not to the earth."

This may have already been said or implied, but the voltage to ground of an ungrounded xformer secondary is indeterminate.
Because of interwinding parasitic capacitance, the secondary voltage may float up to the primary voltage, or it may not because winding capacitance to ground may overwhelm the other capacitances.
Grounding the center tap somewhere makes the secondary voltage with respect to ground predictable and independent of stray capacitance; that is, a max of 150vrms.

Mr. 75, there is more to that article than meets the eye. It may save lives.

As long as it makes sense to you....

Yoyizit · 08-04-2008, 08:26 PM

Quote:

Originally Posted by chris75

As long as it makes sense to you....

There I go again!

jrclen · 08-04-2008, 09:36 PM

Quote:

Originally Posted by Joe F

OK. I'll run a new ground wire back to the panel. What size wire do I need for a 200 amp service?

#4 copper with no splices.

Joe F · 08-05-2008, 09:47 AM

Quote:

Originally Posted by jrclen

#4 copper with no splices.

Thanks.

For a minute there I thought I was going to have to change all the DiLithium crystals.

Yoyizit · 08-05-2008, 10:17 AM

Quote:

Originally Posted by Joe F

Thanks.

For a minute there I thought I was going to have to change all the DiLithium crystals.

After any encounters with The Borg it is recommended to routinely change all the crystals.
And check your anti-matter pods.

jrclen · 08-05-2008, 10:48 AM

Quote:

Originally Posted by Joe F

Thanks.

For a minute there I thought I was going to have to change all the DiLithium crystals.

LOL. Sometimes we forget there is an OP (original poster) waiting for an answer.