Electrode grounding conductor

[bob overfield]

Art.250 States that we can use any of the grounding electrodes that are available. Metal water pipe, metal frame of the structure, concrete encased (Ufer), ground ring, rod or pipe and plate electrodes.
Art.250.52 (3) States the concrete encased electrode conductor cannot be smaller than number four copper.
Art. 250.66(B) States the grounding conductor for the concrete encased electrode shall not be larger than number four copper.
Does this mean that an electrical contractor can use a number four copper grounding conductor to a concrete encased electrode for any size of electrical service?

 

[ryan_618]

Re: Electrode grounding conductor

You got it!

Well, almost. If the designer specifies a larger conductor (and they often do), you will have to comply with their requirements. I remember installing my share of Ufer ground conductors larger than #4.

[ September 29, 2003, 05:38 PM: Message edited by: ryan_618 ]

 

[bennie]

Re: Electrode grounding conductor

Ryan: Have any of the designers ever explained why they require larger ground electrode conductors?

Do they own copper mining stock?

 

[gwz2]

Re: Electrode grounding conductor

250.50 If available - - -, each item in 250.52(A)(1) thru (A)(6) SHALL be bonded together to form the GES. - - -.

Don't forget the other GE's that may be available on the the premise.

 

[ryan_618]

Re: Electrode grounding conductor

Bennie: It makes me wonder! I used to frame houses when I was in high school and wondered if some of the engineers and/or inspectors owned stock in the simpson strong tie company. (I only wish I was joking...I'm not!)

EDIT: I rememember GEC sizing for rods being brought up here and one of the EE's (Charlie B?)stated that he/she often spec'd out larger conductors than #6 for a rod and their reason was for the conductor being less likely to break or get damaged.

[ September 29, 2003, 06:28 PM: Message edited by: ryan_618 ]

 

[roger]

Re: Electrode grounding conductor

Bob, to show GWZ's point in a picture.

The point about whether a made GEC has to be any larger than code requirement is a different conversation.

Roger

 

[tonyi]

Re: Electrode grounding conductor

Originally posted by bob overfield:
Art. 250.66(B) States the grounding conductor for the concrete encased electrode shall not be larger than number four copper.

Shall not be REQUIRED to be larger than a #4. Big difference

 

[iwire]

Re: Electrode grounding conductor

Tonyi I did not see anyone say that it would be against code to run larger than 4 AWG.

Do you have reason to believe that he should run larger than 4 AWG?

 

[dereckbc]

Re: Electrode grounding conductor

Bob O, do not go away thinking that if you have a service conductor size of 3/0 copper or larger you can install a # 4 AWG GEC from the grounded service conductor to the ufer GE unless the ufer is the only GE. In the scenerio Roger demostrated you would have to provide a 250.66 sized GEC from the grounded service conductor to the first GE, then bond the ufer with a # 4 AWG.

[ September 29, 2003, 08:36 PM: Message edited by: dereckbc ]

 

[tonyi]

Re: Electrode grounding conductor

Originally posted by iwire:
Tonyi I did not see anyone say that it would be against code to run larger than 4 AWG.

Do you have reason to believe that he should run larger than 4 AWG?

Bob O. missed a few critical words in his original post making it seem #4 was the max. You don't have to go larger, but you could if circumstances warranted it (like maybe you had some #2 cutoffs on hand that were just the right length )

 

[bob overfield]

Re: Electrode grounding conductor

Say you have a six-plex building, a six hundred amp. service whith no metal water pipe and no building steel. The general has installed a concrete encased rebar for the electrician. There are no electrical specs for this building requiring a larger than number four copper.This job was up for bid, do you think that the electrical contractor will install a larger than number four copper GEC?

 

[dereckbc]

Re: Electrode grounding conductor

Originally posted by bob overfield:
do you think that the electrical contractor will install a larger than number four copper GEC?

Not required if there are no othe GE's availible. However if I were designing it, I would add two ground rod electrodes with a GEC from the grounded service conductor sized per 250.66, then bond the ufer with a #4 AWG.

[ September 30, 2003, 10:44 AM: Message edited by: dereckbc ]

 

[roger]

Re: Electrode grounding conductor

If you have to bid this job you would only bid what was asked for. (or the minimum allowed)

You can't stay in business if you don't bid apples to apples or oranges to oranges with your competitors. This would mean a #4.

Roger

 

[pierre]

Re: Electrode grounding conductor

Dereck

Why do you feel the need for the ground rods?

Pierre

 

[bob overfield]

Re: Electrode grounding conductor

Would the ground rods have to be six feet from the concrete encased Ufer?

 

[ryan_618]

Re: Electrode grounding conductor

Originally posted by bob overfield:
Would the ground rods have to be six feet from the concrete encased Ufer?

No. Refer to article 250.56

 

[bob overfield]

Re: Electrode grounding conductor

As I understand the NEC the ground rods are not required, but many of the inspectors would require you to use them. Could a fellow run the GC through the acorn clamp of the Refer and connect it to a single rod? He would have the two electrodes effectively boned together.

 

[jxofaltrds]

Re: Electrode grounding conductor

Bob

"As I understand the NEC the ground rods are not required,"

Read 250.53(D)(2).

While responding to this I read 250.53(A).

"Where practical" "embedded below permanent moisture level"

What are they saying. Never really read this one before.

Mike P.

 

[dereckbc]

Re: Electrode grounding conductor

Originally posted by pierre:
Dereck

Why do you feel the need for the ground rods?

Strictly a design preference on my part, not a code requirement. If the ufer is all that is availible, then that is all that has to be used.

I have had a few problems with a ufer before and prefer to supplement. Roger is correct if it was not asked or specified, do not add it to a bid.

[ September 30, 2003, 05:29 PM: Message edited by: dereckbc ]

 

[bob overfield]

Re: Electrode grounding conductor

259-53(A) as I understand this art. it says you cannot install a ground where it will be covered by black top, concrete or such. Drilling a hole into the hard surface and driving the rod would be a no-no-