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sizing of service conductors #170314 10/31/07 01:07 PM
Joined: Sep 2007
Posts: 7
stator Offline OP
New Member
I have an apartment complex that im installing a 1300 amp meter bank assembly (13 meter sockets, 1 main disconnect)this will be an overhead single phase 120/240 service. The point of attachment for power co. is about 20' above the meter assembly. i would amuch appreciate any help here from the board on sizing the service and grounding conductor. im currently in the process of preparing the plans for this project.

Thanks C.L

Last edited by stator; 10/31/07 01:15 PM.
2017 / 2014 NEC & Related Books and Study Guides
Re: sizing of service conductors [Re: stator] #170316 10/31/07 02:42 PM
Joined: Jan 2004
Posts: 1,507
George Little Offline
One would need to know the size of the Service Entrance conductors to size the Grounding Electrode Conductor. When this is known use T. 250.66. You should not have to size this GEC larger than 3/0 cu or 250 KCMIL Alm. You may qualify for a smaller size based on the type of grounding electrode you find available.
Ground rods(s) Max would #6 cu, Concrete encased electrode Max #4 cu.

George Little
Re: sizing of service conductors [Re: George Little] #170317 10/31/07 03:16 PM
Joined: Feb 2003
Posts: 939
frenchelectrican Offline
I will go with 3/0 CU but may i ask about the service size you say 1300 amp ?? this is kinda oddball size if this was on 1200 amp service i can understand then you use the 3/0.

But for ground rod wire useally #6 will do it but becarefull here some area will required larger one typically #4 or larger

Merci, Marc

Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

Re: sizing of service conductors [Re: frenchelectrican] #170321 10/31/07 03:55 PM
Joined: Sep 2007
Posts: 7
stator Offline OP
New Member
I stand corrected The main breaker on this will be a 1400 amp. would these service conductors be parallel?

Re: sizing of service conductors [Re: stator] #170343 11/01/07 10:21 AM
Joined: Dec 2003
Posts: 751
earlydean Offline
Unless these apartments are huge or use a lot of electricity in electric baseboard heat, 1400 amps seems way too big to me. Did you do any calculations???? 13 apartments times 100 amps each doesn't cut it. What is the total square footage? any electric ranges?, electric dryers? kitchen small appliance branch circuits? figure in demand factor per 220 part III or IV.

Re: sizing of service conductors [Re: earlydean] #170365 11/01/07 05:00 PM
Joined: Jan 2001
Posts: 1,044
Tom Offline
You might try looking at some of the examples in Annex D in the back of your code book to get an idea how to calculate the service size needed.

The calculations aren't hard. It will probably take you longer to gather the information than to do the actual calculation.

Few things are harder to put up with than the annoyance of a good example.
Re: sizing of service conductors [Re: earlydean] #170436 11/02/07 08:39 PM
Joined: Sep 2007
Posts: 7
stator Offline OP
New Member
Thanks for the reply, but its already been established what each unit is going to require, My question for the board was what size conductors are needed from point of attachment to line side of disconnect.

Re: sizing of service conductors [Re: stator] #170437 11/02/07 08:57 PM
Joined: Sep 2007
Posts: 7
stator Offline OP
New Member
Thanks Tom, I will look Annex D over.

Re: sizing of service conductors [Re: stator] #170439 11/02/07 09:46 PM
Joined: Oct 2007
Posts: 56
SP4RX Offline
I couldn't agree with earlydean more: 1400 amps seems to be an extremely large service for 13 apts. Thats more than 100 amps each. Who determined that the service should be sized to 1400 amps? Are these unusually large units with air conditioning, hot tubs, and other fancy power hungry appliances? I have seen large machine shops operating lots of huge machinery with many HID lights etc. on smaller services than that.



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