Mulit-Family service conductors

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nicknorth

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When I do a optional load calc on a multi family building do I use table 310.16 to rate the ampacities of the wire or can I use 310.15(B)(6)

Thanks!!
 
Which wire? The text in 310.15(B)(6) is specific on the requirements and on where the table can be used. If there is a single feeder to each unit you can use 31.16(B)(6) for that feeder. If the service is 400A or less you can use the table for the service lateral.

Also remember that just because it's allowed doesn't make it a good design choice.
 
I agree that the service laterals to each dwelling unit can be based on 310.15(B)(6). But that would also be true if you had used the standard method, and not the optional method. Both methods give you the required service size, in amps. Selecting a conductor that has an ampacity of at least that value is a completely separate task.
 
How many services are you using? more than one? I'm starting to do a 20unit condo complex (4000sqft ea) and haven't done one of these before. I'm thinking of doing maybe up to 3 service laterals (1 set) feeding a group of services which will me have the metering on them. My load calc will most likely be around the 2000A area. Any other ideas on the service layout.
Thanks,
Brad
 
hmspe said:
Which wire? The text in 310.15(B)(6) is specific on the requirements and on where the table can be used. If there is a single feeder to each unit you can use 31.16(B)(6) for that feeder.
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I agree.

If the service is 400A or less you can use the table for the service lateral.
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I disagree, if the service is supplying more than one dwelling unit. A service disconnect for a 20-plex rated 400A (presumably one of many) could not use this table, IMO.

310.15(B)(6): For individual dwelling units...
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brad troxel said:
I'm starting to do a 20unit condo complex (4000sqft ea) and haven't done one of these before. I'm thinking of doing maybe up to 3 service laterals (1 set) feeding a group of services which will me have the metering on them. My load calc will most likely be around the 2000A area. Any other ideas on the service layout.
Thanks,
Brad
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Brad, it would be most courteous to the original poster if you started a new thread for your question. But I will say that many jurisdictions require a engineer's stamp on one-lines and load calcs for such a large structure. I would recommend checking before spending much time on it. :)

Edit: I just saw you did post your own question this morning over here. Sorry about that! :)
 
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