I am upgrading a business from a 200amp service to a 320amp service in order to accommodate a 120amp tank-less hot water heater. I know that I need to replace the 200amp meter-base with a 320amp meter-base and K4892 kit. My question is: Will 4.0 Aluminium Triplex Power Feeder Cable be OK, or do I need to upgrade to something like a 350 MCM copper Feeder? Thank you in advance to anyone that can answer this before I get to a 2011 NEC book tomorrow, The Huntsman

The utility's drop is NOT your responsibility, and it is NOT under the NEC's jurisdiction.

I have seen 1200A services fed with 250mcm AL triplex and worse. So I would not be concerned.

Thank you stanfortyman. Here in MO I am required to supply feeder, weather head, and meter base. Ameren MO then connects service to the 36" line hanging from my weather head. I fully agree that it should be their responsibility to connect all of the way to the base. I have used the 4.0 with no problem before but did not know if the 2011 NEC had changed that. I appreciate your response and feel confident to go on with the installation. Sincerely, Joel H.

I see on page 30, note #1, of Ameren requirements:

http://www.ameren.com/source/ConstSe...viceManual.pdf

1. Overhead service drops and the connections at each end of the service drop will be owned, installed, and maintained by Ameren.

You should consult with Ameren about this.

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Originally Posted by thehuntsman

Here in MO I am required to supply feeder, weather head, and meter base. Ameren MO then connects service to the 36" line hanging from my weather head. I fully agree that it should be their responsibility to connect all of the way to the base.

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No, that's not what I meant.
The "service drop" is only the overhead to the structure. From the weatherhead down to the meter is almost always customer responsibility.

Thank both of you tkrussel and stanfortyman. You both were very helpful. It seems as if it just depends on which engineer comes out to inspect and where the installation is. Either way, the weather head and meter base are installed with the head being 24" above the roof line and 3' of 4.0 hanging from it. I will call Ameren MO Monday AM for service hook-up. I really appreciate your immediate responses to my question. I wish you all much prosperity, Joel Huntsman