ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

Status
Not open for further replies.

timz

Member
Location
Michigan
WE HAVE TWO DORMITORY'S, DORM 1 AND DORM 2. DORM 1 HAS A 480/277 VOLT SERVICE. THIS SERVICE WILL FEED DORM 2 THROUGH A 1600 AMP BREAKER. DORM 2 IS NEXT DOOR TO DORM 1 OWNWED BY SAME UNIVERSITY. DORM 2 IS FED BY PVC UNDERGROUNG CONDUITS,AND THERE IS NO METALLIC OR STEEL CONNECTION BETWEEN THESE BUILDINGS. THIS FEED WILL TERMINATE RIGHT TO THE MAIN BUSS IN DORM 2,NO MAIN DISCONNECT. THE DISCONNECT IS IN DORM 1. MY QUESTION IS DO I NEED TO PULL GROUNDING WIRES WITH MY FEEDERS OR CAN I TREAT THE FEEDER AS A NEW SERVICE AT DORM 2. THANK YOU
 

bennie

Esteemed Member
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

Are these dorms connected with a covered walkway?
 

charlie

Senior Member
Location
Indianapolis
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

Sorry, I have a tough time believing that there will be no metallic paths now or any time in the future between these two buildings (although you can't control the future and the Code is not written for the possibilities). No metal piping systems, metallic shields on communications cables, not so much as a gas line? My personal preference is that you pull a grounding conductor.

If all that is true and you can live with it, the Code doesn't prohibit the installation. Don't overlook the question that Bennie has asked.
 

dereckbc

Moderator
Staff member
Location
Plano, TX
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

I have got to go with Bennie and Charlie suspicions. To CYA, I would run a grounding conductor. No matter what you will be covered. In addition, I would establish a ground electrode at Dorm two, just for lightning safety.
 

eprice

Senior Member
Location
Utah
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

Originally posted by timz:
...THIS FEED WILL TERMINATE RIGHT TO THE MAIN BUSS IN DORM 2,NO MAIN DISCONNECT. ...
which exception to 225.32 do you intend to use to justify no main disconnect at the 2nd building?
 

tom baker

First Chief Moderator
Staff member
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

Preferred method is not to reground the neutral at the second building. In fact, Washington State will no longer allow seperate buildings or structures to have the neutral to be regrounded after Aug 1, 2003. Mike Holts 2002 Grounding and Bonding text has an excellent review of the objectionable current your proposed method may create.
Your seperate building (dorm) requires a main disconnect.
Also the second building will require a grounding electrode system per 250.30.
 

bennie

Esteemed Member
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

Price is right, there has to be one that will work :)
 

Nick

Senior Member
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

Provided you qualify for one of the exceptions to 225.32 (as eprice has stated) then 250.32(D) would apply. It does not give you a choice. You have to pull an EGC and you cannot connect the grounded conductor to the second buildings grounding electrode system.

Hi Bennie! Glad to see you again.

[ March 10, 2003, 09:48 PM: Message edited by: Nick ]
 

bennie

Esteemed Member
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

Does anyone have a problem with using the smaller wire when a large one is available for fault clearing?
 

timz

Member
Location
Michigan
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

BENNIE, SORRY ABOUT THE INFO. THERE MAY BE A WALKWAY BETWEEN THE BUILDINGS BUT THE GENERAL IS NOT CERTAIN AT THIS TIME. THERE WILL BE A MAIN DISCONNECT IN DORM 1 FOR DORM 2 AT THE COMMON SERVICE . I ALSO AGREE WITH EVERYONE THAT GROUNDING CONDUCTORS SHOULD BE PULLED AS NOTED IN SEC 250.32{D} PER 2002 NEC, BUT I'M OVER RULED BY FOREMAN ON JOB.
 

eprice

Senior Member
Location
Utah
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

Originally posted by timz:
...THERE WILL BE A MAIN DISCONNECT IN DORM 1 FOR DORM 2 AT THE COMMON SERVICE...
Unless the building qualifies for one of the exceptions to 225.32, that section requires the main disconnect for dorm 2 to be at dorm 2. A disconnect at dorm 1 would not count.
 

hornetd

Senior Member
Location
Maryland
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

Unless the data cables and telephone cables for these dorms are fiber optic you had better pull an EGC. If you don't you may find neutral current travelling on the telephone cables and the campus local area network and that will get reeal expensive. You may find yourself at the head of the line when the customer starts looking for someone to blame.
--
Tom
 

bennie

Esteemed Member
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

Tom: Wouldn't the neutral/ground conductor have less impedance than an equipment ground conductor?

Is one of the telephone wires grounded?
 

stars13bars2

Senior Member
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

timz
What happened to the approved plans with the engineers stamp that shows the required the main disconnect? This was not a design build project was it?
stars
 

hornetd

Senior Member
Location
Maryland
Re: ONE BUILDING FED FROM ANOTHER BUILDING ON SAME PREMESIS

Originally posted by bennie:
Tom: Wouldn't the neutral/ground conductor have less impedance than an equipment ground conductor?

Is one of the telephone wires grounded?
The tip conductor of each pair is grounded at the exchange but that is not the issue. The copper sheild of underground telephone cable is bonded to the building grounding electrode system at the network protectors in each building. The messenger of overhead multi pair cable is also bonded at the protectors. The lower impedance of the grounded conductor will not save you from some parrallel neutral current flow over the unintended pathway. The presence of stray AC current on that telephone cable sheild or messenger plays hell with signal quality. If the neutral between the two buildings ever fails that shield or messenger would carry substantial current which may cause it to fail and energise the individual pair conductors.
--
Tom
 
Status
Not open for further replies.
Top