Parallel Residential Service

[george t. everett]

Re: Parallel Residential Service

Pierre. They are citing the Residenial code of New York. The problem is not the 2-200 amp main disconnects, but the cable from the pole or transformer to the meter,which becomes a true parallel run. I am located in the eastend of Long Island. I don't have a copy of the Residenial Code of New York so it makes it hard to referance. Thanks for your help!

 

[websparky]

Re: Parallel Residential Service

Hi george,

After following this thread, I'm wondering if we/they are reading the code properly?
What I mean is, the code states "3-Wire" services.
This may be their understanding of the code as opposed to "parallel" feeders?

"120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders"

Just a thought,
Dave

 

[pierre]

Re: Parallel Residential Service

George
I totally forgot to look in the New York Residential Building Code, new as of January 1 of 2003. The inspector is 100% correct. He is on the ball and I offer my apology to him for stating otherwise. For single family dwellings in ALL OF NEW YORK STATE other than NYC, this code supercedes the NEC. I just took a 'peek' at it and it is in 'black and white'. Parallel with 4/0. It is on page 422, Table E3503.1

Pierre

 

[george t. everett]

Re: Parallel Residential Service

Pierre, I don't have a copy of the Residenial Code of New York. What other things should I look out for? I believe it states that AFCI's are not required. Thanks for the help in clearing up this confusion.

 

[hornetd]

Re: Parallel Residential Service

I am at a loss to understand how we can treat two separate sets of conductors as "the main power feeder to a dwelling unit." Once we break the load up into two or more separate panels serving the same dwelling unit the diversity on which the ampacities allowed by 310.15 (B) (6) are based can no longer be assured. I have seen several two panel installations in which one panel is very heavily loaded and the other carries very little load. I have serviced one such installation were the load in one panel was 190 amperes and the other carried less than fifty. I have always based the conductor ampacity for two or more disconnects supplied from a common service on the tables in 310.16. Am I the only one that sees a potential for overloading these conductors?
--
Tom

 

[curt swartz]

Re: Parallel Residential Service

It sounds like this code was written by carpenters or plumbers. Why would parallel 4/0's be required for a 400 amp residential service but parallel 3/0's can be used for 400 amp commercial services and feeders?

Pierre,
It did say 4/0 CU didn't it? If it was parallel 4/0 AL conductors then I would agree with book.

Tom,
Were talking about parallel service conductors which would be 1 set of conductors so the total load on them using your example would be 240 amps (190 + 50). I agree with you that once the load is separated into multiple feeders table 310.15(B)(6) can not be used. If this set of service conductors splits off to 2 separate panels after the meter socket I would require 3/0 CU to each panel.

 

[hornetd]

Re: Parallel Residential Service

Curt
Thanks for your answer. I have always believed that only a single set of conductors to any given residence can be sized to 310.15 (B) (6). Once you route separate sets of conductors to two different panels serving the same residence I believe you should size by 310.16.
--
Tom

 

[jro]

Re: Parallel Residential Service

George T is talking about a 400amp service (line side), on the load side of the service it all changes, you could install a 100amp MB panel, and the extra amps, if you will, could be for future expansion, would you feed the 100amp panel with 3/0 cu or 4/0 cu according to New York standards, or #4 cu, in this residential application, so in my opinon feeding the two 200amp panels each with 2/0 cu would be ok, as george clearly states the load side wires of the meter base are no longer in parallel. Now if the electrician overloads one panel he should not be in the trade. Now grill me

 

[hbendillo]

Re: Parallel Residential Service

I am not involved in residential work. What is the logic for Table 310.15(B)(6)? Why do we need this confusion? What was wrong with requiring 3/0 parallel conductors for a 400-amp circuit? That is what I would insist upon in commercial work. Is the code saying that we oversize residential service conductors so much that we need to have a different table. Why not just install a smaller service?