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jerryrevels

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Situation: Comericial project on a military base with no out side inspector. The configuration is 3 generators feeding 2 transfer switches; transfer switch #1 is being fed form the 2nd tranfer switch and gen # 1. Transfer switch #2 is being fed form gen #2 and #3. Each transfer switch feeds one MDP. The MDPs are on a steal errected platform. Each MDP feeds to Several SDPs that are located at form 75' to 175' away at the facilities they are providing power to.
Question: can a concrete encased electrode in a slab. with footers, being used for containment for one of the generators qualify as the sole grounding electorde for the Main distrobution panels on the steal platform that is detached by 10' form the generator slab?
 

One-eyed Jack

Senior Member
Situation: Comericial project on a military base with no out side inspector. The configuration is 3 generators feeding 2 transfer switches; transfer switch #1 is being fed form the 2nd tranfer switch and gen # 1. Transfer switch #2 is being fed form gen #2 and #3. Each transfer switch feeds one MDP. The MDPs are on a steal errected platform. Each MDP feeds to Several SDPs that are located at form 75' to 175' away at the facilities they are providing power to.
Question: can a concrete encased electrode in a slab. with footers, being used for containment for one of the generators qualify as the sole grounding electorde for the Main distrobution panels on the steal platform that is detached by 10' form the generator slab?

Not the sole GE, but IMO you can supplement with one grd rod and be good to go.
 

e57

Senior Member
  1. Check your spec's - any advice is worthless unless you're meeting what you were hired to do.
  2. You want to put a single electrode 10' away - then 75-175' away and call it done... These are multiple structures 250.32 applies - there should be an electrode at minimum at the MDP's AND at the generators, and be sure to check to see what is at the facilities they serve - there too definatly. (FYI - military re-fuelers are require to ground prior to pumping so it would not be a bad idea to make that one acessible - if you need to. Unless there is a ground on the frame of the generator.)
  3. Check which code you are on - '05 says some things that are very different than the '08 both with 250.32, and an addition code of 250.35 that looks like it applies to you.
 

One-eyed Jack

Senior Member
Sure would want to see a code reference for that.

CEEs can be a sole electrode.

250.53(D)(2) requires supplemental electrodes for water line electrodes and be of a type specified in 250.52(A)(2) thru (A)(8). (A)(3) being a CEE. If the CEE can be the sole electrode and we must use any and all that are present we seem to have a conflict with your statement that the CEE can be the sole electrode. Hence IMO a grd rod would be required. I know there was no mention of a water line I am just stating that there is a precedence where a CEE can NOT be the sole electrode. No one ever said it is supposed to make sense.:D
 

augie47

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Sorry, I don't see the precedence (or requirement).
250.52 lists grounding electrodes, 250.50 requires all present to be bonded together and 250.53(C)(2) requires a supplemental electrode for a water pipe (and only a water pipe).
I see nothing requiring a rod be added in any other situation.

In defense of your statement, I see no requirement to use the CEE as it is not a part of the structure with the MDPs but due to it's preference as an electrode and it's proximity, I would have no problem with it being used.
(the ground rod, if used, could also be 10 ft away)
 
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iwire

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If you don't consider the steel platform a structure;which it is. You would not have to comply with 250.32 (A) and a ground rod only would comply at that point.;)

I am not following you.:)

IMO the platform is a structure and is required to have a grounding electrode system at it.

If the only ground electrode that exists is a CEE we are done, we do not have to add another one.
 

roger

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If you don't consider the steel platform a structure;which it is. You would not have to comply with 250.32 (A) and a ground rod only would comply at that point.;)

I agree with Bob, I am not following you either. It doesn't matter what structure we are looking at, if a CEE is the only GE present for a structure it would be the only one needed, we don't have to augment it with another.

Roger
 
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One-eyed Jack

Senior Member
I am not following you.:)

IMO the platform is a structure and is required to have a grounding electrode system at it.


250.32 (a) allows either a rod or a GES

If the only ground electrode that exists is a CEE we are done, we do not have to add another one.

The cee is at a separate location although close to the platform. TWO different structures in the same general area but "two". For example ,slab on grade residence with a cee. A detached garage with a 100 amp feeder to a 20 circuit panel. Dwelling and garage are 8 ft apart. Is a ground rod required at the garage? IMO yes. In the begining the cee was the only electrode that existed.
 
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roger

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A detached garage with a 100 amp feeder to a 20 circuit panel. Dwelling and garage are 8 ft apart. Is a ground rod required at the garage? IMO yes. In the begining the cee was the only electrode that existed.

Not if the detached garage has a CEE and even if it doesn't, what prevents us from using a longer GEC and using the existing CEE for the other structure? It would seem to me to be an advantage to have a length of conductor in contact with the earth on it's way to the electrode.

Roger
 
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iwire

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250.32 (a) allows either a rod or a GES

250.32 requires an electrode, what kind of electrode that is does not mater.

As far the rest, if you want to say 10' puts the CEE to far away from the MDP in the OPs post I guess that is within your authority but I think it is kind of ridiculous.

What if the ground rod you ask me to add is 12' away?
 

One-eyed Jack

Senior Member
250.32 requires an electrode, what kind of electrode that is does not mater.
True, I did not mean to imply that a rod was the only acceptable electrode. The emphasis was that a GES was not absolute..
As far the rest, if you want to say 10' puts the CEE to far away from the MDP in the OPs post I guess that is within your authority but I think it is kind of ridiculous.
At no point have I ever said or implied that the distance was relevant. The ridiculous is in reading something that was not said or implied.
What if the ground rod you ask me to add is 12' away?
Same answer as above.
 

One-eyed Jack

Senior Member
Not if the detached garage has a CEE and even if it doesn't, what prevents us from using a longer GEC and using the existing CEE for the other structure? It would seem to me to be an advantage to have a length of conductor in contact with the earth on it's way to the electrode.

Roger
Who said the garage had a CEE? FYI this is an electrode.
Nothing!
 
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iwire

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Jack I am entirely lost.:confused:

Here is the OPs question.

Question: can a concrete encased electrode in a slab. with footers, being used for containment for one of the generators qualify as the sole grounding electorde for the Main distrobution panels on the steal platform that is detached by 10' form the generator slab?


The opening post has a CEE not more than 10' from his MDP, he does not need to add a rod he has a CEE and that is all that the NEC requires.
 

One-eyed Jack

Senior Member
Jack I am entirely lost.:confused:

Here is the OPs question.




The opening post has a CEE not more than 10' from his MDP, he does not need to add a rod he has a CEE and that is all that the NEC requires.

The platform is a second structure and it must be bonded,grounded etc. Whether he chooses to run a gec to the platform from the CEE or use a rod,plate or any other approved electrode it gets done. Regardless of how it is grounded at the site it will always be a violation of the NEC because of the grd at the POCO transformer location. Parallel paths? The steel platform has always had the potential to be an electrode in and of itself. As such it would be required to supplement the CEE because it exists.
 
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