Grounding Conductor in Pipe or Pad?

[FESApprentice2496]

I'm going to try to explain this as best as possible. There is an existing 6000A switchgear in the basement of the building were remodeling. The service conductors from the power company come into the gear and land on the busbars. We are adding a second service (1600A) to the building so the owners can monitor each individual apartment's power usage. The existing switchgear is on the right side of the electrical room and the new disconnect and meter stacks on the left. On the back wall there are 3 conduits on the floor that run from the gear to the new disconnect. The pipes are being encased in concrete which is going to create a raised pad/surface in the room. Conductors are 600MCM Grounding wire is 3/0. I'm confused if I can run Black, Red, Blue, Neutral in each pipe and run one 3/0 THHN ground along the outside of the pipes so the grounding wire will be encased in concrete afterward. Or do I need to Run a ground in each pipe, so it would be Black, Red, Blue, Neutral, Ground. We were talking about it at work and going back and forth on it. i looked in the code and have read it both ways. Id like some explanation and some code articles along too.

Thanks

 

[augie47]

Sorry, I'm unclear. Is your new switchgear connected on the LINE (service) side of the old gear or on the LOAD side of a OCP device ?

 

[don_resqcapt19]

In general, the EGC must be installed in the raceway. 300.3(B).

 

[FESApprentice2496]

Sorry, I'm unclear. Is your new switchgear connected on the LINE (service) side of the old gear or on the LOAD side of a OCP device ?

my faught I forgot to add that is line side.. its is unprotected power.. and that's where we are tapping onto. The reason for the concrete pad...

 

[augie47]

If it's "unprotected" the it would be "service" (I think you already knew this... just clarifying).

You would not need a equipment grounding conductor in your conduits as your grounded conductor serves for grounding.
You would need to assure that all enclosures and your conduits are bonded, but that can be accomplished bu the use of bonding jumpers to your grounded conductor/buss. (Your 3/0 could also be used for bonding)

Don pointed out the basic rule in post #3.

Curious... does your 1600 amp service have a main ? I ask as your 600 kcmil would only be good for a 1200 amp main (1400 max under 90? termination rules)

 

[FESApprentice2496]

If it's "unprotected" the it would be "service" (I think you already knew this... just clarifying).

You would not need a equipment grounding conductor in your conduits as your grounded conductor serves for grounding.
You would need to assure that all enclosures and your conduits are bonded, but that can be accomplished bu the use of bonding jumpers to your grounded conductor/buss. (Your 3/0 could also be used for bonding)

Don pointed out the basic rule in post #3.

Curious... does your 1600 amp service have a main ? I ask as your 600 kcmil would only be good for a 1200 amp main (1400 max under 90? termination rules)

hmm I forget now that you mention it I'll have to check tomorrow, I don't know if thats a typo or thats what I meant now. yea its a Main disconnect.

ok thats what I was wondering. its PVC conduit. So is it neccessary to even run a 3/0 on the outside?

 

[augie47]

hmm I forget now that you mention it I'll have to check tomorrow, I don't know if thats a typo or thats what I meant now. yea its a Main disconnect.

ok thats what I was wondering. its PVC conduit. So is it neccessary to even run a 3/0 on the outside?

Keep in mind, if you have a MAIN, and it's over 800 amp, the conductor amapcity must be equal to or exceed the rating on that main.
If you have PVC conduit, sight unseen, I see no need for the 3/0... period.
Your old service gear should be bonded to the neutral as well as your new.
You would, IMO, need grounding electrode conductors from you new service to the electrodes, water, etc and some of those might need to be 3/0 but they do not need to be in your conduits.

 

[infinity]

I agree, if these are service entrance conductors then you would not install the #3/0 at all.

 

[Smart $]

Has the plan been approved for construction by the AHJ? I'm asking because service disconnects are required to be grouped. Yours will be on opposite sides of the electrical room.

For the posted topic, you don't use EGC's on the line side of a service disconnect... you use GEC's and bonding jumpers. Assuming your 6000A gear is properly "earth" grounded, you will have to irreversibly connect a GEC tap to the existing GEC(s) and run it to the new disconnect. This GEC tap can be on the outside of the encased conduits.

 

[FESApprentice2496]

Has the plan been approved for construction by the AHJ? I'm asking because service disconnects are required to be grouped. Yours will be on opposite sides of the electrical room.

For the posted topic, you don't use EGC's on the line side of a service disconnect... you use GEC's and bonding jumpers. Assuming your 6000A gear is properly "earth" grounded, you will have to irreversibly connect a GEC tap to the existing GEC(s) and run it to the new disconnect. This GEC tap can be on the outside of the encased conduits.

I think that's the issue, there is talk of trying to get around running to the electrodes so by running that 3/0 inside the pipes or 1 outside that's tapping onto the old services electrodes

The building has been approved it really has prolly 10 breakers to turn off to shut down the whole building... Must be grandfathered

 

[FESApprentice2496]

so thats legal to do? just tap off the ground bar with the electrodes of the existing service to the new service with 1 3/0?

 

[augie47]

so thats legal to do? just tap off the ground bar with the electrodes of the existing service to the new service with 1 3/0?

Tapping off the ground bar in the existing panel for your new grounding electrode conductors would not be compliant.
Tapping of a properly sized grounding electrode conductor outside of the existing panel would be.
See NEC 250.64(D).
In your situation, a 3/0 grounding electrode conductor could be routed from the new gear grounded buss and tapped to a 3/0 say going to the metallic water system or building steel. It could, of course, go directly to the electrode(s), but a tap might be a shorter distance.

 

[FESApprentice2496]

Tapping off the ground bar in the existing panel for your new grounding electrode conductors would not be compliant.
Tapping of a properly sized grounding electrode conductor outside of the existing panel would be.
See NEC 250.64(D).
In your situation, a 3/0 grounding electrode conductor could be routed from the new gear grounded buss and tapped to a 3/0 say going to the metallic water system or building steel. It could, of course, go directly to the electrode(s), but a tap might be a shorter distance.

thats kind of what I thought. Looking at that article it says Service, not Service(S). Same rules apply? I guess its an odd situation for what the situation is so everything gets jumbled up and confusing.

 

[Smart $]

thats kind of what I thought. Looking at that article it says Service, not Service(S). Same rules apply? I guess its an odd situation for what the situation is so everything gets jumbled up and confusing.

It is a service, no (S) for plural... i.e. one service with multiple disconnecting means enclosures. "The" rule applies... 250.64(D).

 

[Smart $]

Tapping off the ground bar in the existing panel for your new grounding electrode conductors would not be compliant.
Tapping of a properly sized grounding electrode conductor outside of the existing panel would be.
....

I don't recall it being require to be tapped outside the existing enclosure. I'm thinking it could be irreversibly tapped inside the exisitng enclosure to an existing full-sized GEC? ...just not the ground bus, or anything else for that matter

 

[augie47]

I don't recall it being require to be tapped outside the existing enclosure. I'm thinking it could be irreversibly tapped inside the exisitng enclosure to an existing full-sized GEC? ...just not the ground bus, or anything else for that matter

I am led to believe that "outside the enclosure" is the intent of 250.64(D)(3) "common location". I recall the discussion from a seminar where it was explained the intent was not to loose the electrode connection if one service means was removed or altered..
Admittedly, it is not "code", but notice Mike's graphic shows that also.

 

[Smart $]

I am led to believe that "outside the enclosure" is the intent of 250.64(D)(3) "common location". I recall the discussion from a seminar where it was explained the intent was not to loose the electrode connection if one service means was removed or altered..
Admittedly, it is not "code", but notice Mike's graphic shows that also.

Okay, I understand... better design choice, but not Code required.

But in this case, I don't believe it is much of a better design choice. The service entrance tap conductors for the being-added disconnecting means originate in that enclosure.

 

[augie47]

Okay, I understand... better design choice, but not Code required.

But in this case, I don't believe it is much of a better design choice. The service entrance tap conductors for the being-added disconnecting means originate in that enclosure.

Just to be clear, as I read and understand it, 250.64(D) requires it not to be tapped in a service enclosure. That's my OPINION. You are welcome to yours and, as I find you unwavering (also ) I am not going to entertain a spitting contest over Code wording. Neither you or I will be inspecting the job so the only opinion that really matters is the his AHJ's.
It very well could be read either way and, rather than male this another "Kindly advise" ongoing thread, I will leave this as my opinion and move on. Others can take it or leave it.

 

[Smart $]

Just to be clear, as I read and understand it, 250.64(D) requires it not to be tapped in a service enclosure. That's my OPINION. You are welcome to yours and, as I find you unwavering (also ) I am not going to entertain a spitting contest over Code wording. Neither you or I will be inspecting the job so the only opinion that really matters is the his AHJ's.
It very well could be read either way and, rather than male this another "Kindly advise" ongoing thread, I will leave this as my opinion and move on. Others can take it or leave it.

So noted :blink:

 

[FESApprentice2496]

thanks guys, yea I think we are just going to tap off the rebar electrode in the panel. MY AHJ is somewhat lax so it should be alright either way.

So noted :blink: