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#95958 - 10/26/05 08:39 PM Service Laterals  
Gee  Offline
Junior Member
Joined: Oct 2005
Posts: 9
baton rouge LA, USA
hey guys great site,I might stick around.

but I have an urgent question for now.

I have a 208v, 3 phase, service lateral
(pad mount xformer secondary) feeding a 1600 Main breaker switch board.
In the past the utility company has run the secondarys, now they are requiring the customer to provide them.
The local utility had always undersized them IMO. Now that we must provide them, am I right in assuming that we must size these greater than the service main, in this case 4 sets of 500 MCM cu. ?

The project engineer tells me to run 4 sets of 350 MCM, however it is my opinion that this does not meet the NEC and 500 MCM conductors are required.

I hope I was clear with my question. and thanks in advance..


2017 / 2014 NEC & Related Books and Study Guides

#95959 - 10/26/05 10:22 PM Re: Service Laterals  
JBD  Offline
Member
Joined: Jul 2001
Posts: 599
WI, USA
Even 4 sets of 500kcmil is not adequate. 500kcmil is only rated for 380A at 75C (the rating of the terminations in the service gear). Above 800A you are not permitted to round up.


#95960 - 10/26/05 11:23 PM Re: Service Laterals  
Bob  Offline
Member
Joined: Feb 2002
Posts: 182
Mobile, AL, USA
JBD is right again. 4 sets of 500 kcm is good for 1520 amps. You will need 4 sets of 600 kcm at 420 amps for a total of 1680 amps as per 240.4C.


#95961 - 10/27/05 06:04 AM Re: Service Laterals  
winnie  Offline
Member
Joined: Sep 2003
Posts: 649
boston, ma
Is there any chance that these are still _specificed_ by the POCO using their sizing rules, even though they are to be installed by the customer's electrician?

-Jon


#95962 - 10/27/05 09:55 AM Re: Service Laterals  
Gee  Offline
Junior Member
Joined: Oct 2005
Posts: 9
baton rouge LA, USA
Correct you are about 600 MCM. I'm not doing my own math here.
The laterals were not specified by the power co. The project engineer specified the laterals on plans. Later admitting that they resized the MDP during the design and forgot the increase the service laterals.
The engineers later asked for change order pricing to increase to 4 sets #500MCM. ( thats where I got the #500). Now the owner has said he will not approve any additional funds. So the engineer has stated my change order request will not be approved. I am concerned about my liabilty in this issue due to not meeting the NEC. This project has turned very bad due to some other issues with design oh which I am taking a beating due to the engineer's faults. I really do not want to butt heads with the engineer and harm a relationship for future projects, But I do not think I have a choice. Anyone else have any ideas ?


#95963 - 10/27/05 10:43 AM Re: Service Laterals  
Roger  Offline
Member
Joined: May 2002
Posts: 1,716
N.C.
Gee,
Quote
the project engineer specified the laterals on plans. Later admitting that they resized the MDP during the design and forgot the increase the service laterals.
The engineers later asked for change order pricing to increase to 4 sets #500MCM. thats where I got the #500).
the engineer admits his mistake here and does the right thing by asking you to submit a change order.

Quote
Now the owner has said he will not approve any additional funds. So the engineer has stated my change order request will not be approved.
So now he is in effect saying, "my mistake will come out of your pocket, not mine".

The engineer has Errors and Omissions insurance that would cover his mistake if he can not come to an agreement with the owner.

Whatever happens you should not entertain the thought of making the correction at your expense even if this strains your relationship with this engineer.

Roger


#95964 - 10/27/05 12:05 PM Re: Service Laterals  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
What is the actual calculated load? If it is 1400 amps or less, install a second service disconnect and the 4 sets of 350.
Don


Don(resqcapt19)

#95965 - 10/27/05 04:22 PM Re: Service Laterals  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Don has a great idea here. [Linked Image]

You could go with two 800 amp service disconnects eliminating the need for GFP and allowing the use of the 350s or 500s depending on the calculated load.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#95966 - 10/27/05 04:35 PM Re: Service Laterals  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Watch out for 240.21(C)(4). This would have you terminating in a single overcurrent device.


George Little

#95967 - 10/27/05 04:54 PM Re: Service Laterals  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
240.21(C)(4) does not apply to service conductors.

Check out 240.21(D)

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts

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