(1) service, (7) electrical rooms - how should we ground?

Status
Not open for further replies.
L

Lee Graves

Member
We're doing a school that has (1) 2000A service which feeds (7) electrical rooms. Each electrical room has (1) 480V panel, a transformer, and (1) 208V panel. The buildings are considered 'separate' for permitting and construction purposes, but they are all connected together with the same building steel. The guys who poured the slab turned up a piece of rebar in each electrical room. Should we connect each transfomer to the building steel and to the rebar, or just to the building steel and abondon the rebar? Will connecting to (7) different pieces of rebar create a difference in potential and create problems?

Thanks for the input,

Lee Graves
 
Lee Graves said:
We're doing a school that has (1) 2000A service which feeds (7) electrical rooms. Each electrical room has (1) 480V panel, a transformer, and (1) 208V panel. The buildings are considered 'separate' for permitting and construction purposes, but they are all connected together with the same building steel.
Click to expand...

If they are 'legally' separate buildings and you have run underground between them in my opinion the requirements of 222.30 and kick in meaning each electrical room will require a main disconnecting means along with other requirements all found between 225.30 and 225.40.

Being 'separate' buildings there is no doubt that 250.32 applies requiring the use of electrodes that comply with 250.50

The guys who poured the slab turned up a piece of rebar in each electrical room. Should we connect each transfomer to the building steel and to the rebar, or just to the building steel and abondon the rebar?
Click to expand...

You do not get to choose, if the electrodes exist you must use them. 250.50

Will connecting to (7) different pieces of rebar create a difference in potential and create problems?
Click to expand...

If we were taking about bonding the same neutral to ground in 7 different places then yes.

But we are talking about bonding only the EGC in several places.

That will not be a problem, it will be a good thing.
 
Lee Graves said:
We're doing a school that has (1) 2000A service which feeds (7) electrical rooms. Each electrical room has (1) 480V panel, a transformer, and (1) 208V panel. The buildings are considered 'separate' for permitting and construction purposes, but they are all connected together with the same building steel...Should we connect each transfomer to the building steel and to the rebar, or just to the building steel and abondon the rebar?Lee Graves
Click to expand...

Sounds to me like 250-32(B)(1) and I agree with Bob in post #2.

I?m also just a curious as mpd questioned in post #5 ?what do the plans show??
 
Status
Not open for further replies.
Top