GEC/multiple disconnects

[augie47]

I'm sure this has been answered before, and I'm embarassed with my experience that I can't put my finger on the answer or Code reference,,,but...
If I have a service consisting of (2) (or more) seperate disconnecting means and I elect to install my GEC to the grounded conductor in the service gear, if I size the GEC per 250-66 for the sum of the service conductors and connect it to #1 service disconnect, is their any requirement that I make any GEC connection to the 2nd service switch?

 

[shortcircuit2]

Re: GEC/multiple disconnects

Although not that clear, 250.24(A)(1) seems to imply that a connection should be made at each service disconnecting means.

Inspectors in my area argue that if one panel burns out and needs replacement, by having a GEC connection at each disconnect you will not lose your ground connection to the other disconnects while repairing the damaged one.

shortcircuit2

 

[suemarkp]

Re: GEC/multiple disconnects

Originally posted by shortcircuit2:
Although not that clear, 250.24(A)(1) seems to imply that a connection should be made at each service disconnecting means.

How do you read that? 250.24(A)(1) says: The connection shall be made at any accessible point from the load end of the service drop or service lateral to and including the terminal or bus to which the grounded service conductor is connected at the service disconnecting means.

I read this as connect the GEC anywhere you want to the neutral between the weatherhead (if overhead) or handhole (if present) or meter and the service disconnecting means. The chosen point just has to be accessible.

Run your GEC to the weatherhead, and you're done. NEC 250.142(A)(1) allows the neutral to do all further grounding of the service equipment.

Inspectors should not deny work based on things that could happen in the future. Who is going to be changing out a service disconnect when the system is live? I don't think I'd want to do that change out in a thunderstorm, GEC or no GEC.

 

[shortcircuit2]

Re: GEC/multiple disconnects

Mark...my answer was in responce to augie47 question on landing the GEC in multiple disconnects...

I understand the multiple locations of terminating the GEC...

Some areas don't consider the meter or CT cabinet as accessible after they are sealed closed...

Connection at the weatherhead or handhole is never done in my area, it is an inconvenient location...

So, when the GEC is landed in the service disconnecting means, inspectors require each of the up to 6 disconnects, when in seperate enclosures, to have a connection to the GEC.

shortcircuit2

 

[augie47]

Re: GEC/multiple disconnects

So, when the GEC is landed in the service disconnecting means, inspectors require each of the up to 6 disconnects, when in seperate enclosures, to have a connection to the GEC.

exactly, and I'm one of those that always has, but I don't like to require what I can't show in writing, and I can't show this.

 

[shortcircuit2]

Re: GEC/multiple disconnects

Thats what I mean about 250.24(A)(1) augie47...the last words of the paragraph state... "at the service disconnecting means"

Well, each of those 6 disconnects is a service disconnecting means, so therefore wouldn't each also require a GEC connection to its grounded conductor at its own terminal or bus?

Thats my interpretation of the words as written...

shortcircuit2

 

[pierre]

Re: GEC/multiple disconnects

250.64(D) Grounding Electrode Taps.
Where a service consists of MORE THAN A SINGLE ENCLOSURE as permitted in 230.71(A), it shall be permitted to connect taps to the common grounding electrode conductor. EACH SUCH TAP SHALL EXTEND TO THE INSIDE OF EACH SUCH ENCLOSURE.

 

[suemarkp]

Re: GEC/multiple disconnects

Originally posted by pierre:
250.64(D) Grounding Electrode Taps.
Where a service consists of MORE THAN A SINGLE ENCLOSURE as permitted in 230.71(A), it shall be permitted to connect taps to the common grounding electrode conductor. EACH SUCH TAP SHALL EXTEND TO THE INSIDE OF EACH SUCH ENCLOSURE.

This is a permissive statement. You can do this if you want and use undersized taps sized per the SEC's feeding each disconnect. If you use the tap method, you'll need to run a tap into each disconnect (which makes sense because you need enough area in tap conductors to add up to the full size GEC).

I think I now see the point shortcircuit2 was trying to make. I take it you agree that if your GEC is outside of the disconnecting means, you can run it from one place and not run taps to the disconnects. But if you choose to run it from a disconnect, you want it run to all such disconnects.

I don't agree with that as a requirement, and I don't see what value it adds. If a full size GEC is adequate when run from the meter or service drop, why would it be inadequate when run from only one disconnect of a multi disconnect install?

Does lightning see any difference if it hits a single 400A enclosure with a 1/0 neutral -vs- hitting two panels each with a 1/0 neutral and a GEC from only one of them?