# service entrance theory



## mrcastrovinci (Jan 10, 2011)

Ok i am trying to wrap my head around this.....

The poco has their own rules when it comes to their wire leading up to your service. If it's triplex ariel cable it can be much smaller then what the code calls for... That's allowed from my understanding because its free air (and yes i know they follow there own code not nec). Now on an underground service why does my cable have to follow nec but theirs doesn't even if its only 3 feet to the main. Whats the theory behind this since it's in the same meter and same conduit type or am i missing something?? Just curious.

Mr Castrovinci


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## Dennis Alwon (May 9, 2009)

mrcastrovinci said:


> Ok i am trying to wrap my head around this.....
> 
> The poco has their own rules when it comes to their wire leading up to your service. If it's triplex ariel cable it can be much smaller then what the code calls for... That's allowed from my understanding because its free air (and yes i know they follow there own code not nec). Now on an underground service why does my cable have to follow nec but theirs doesn't even if its only 3 feet to the main. Whats the theory behind this since it's in the same meter and same conduit type or am i missing something?? Just curious.
> 
> Mr Castrovinci


The poco does not follow the NEC so code means nothing. They base it on the reality of their experience and they supposedly know what will work for them. Most residential wiring is way oversized with service wires. Most 200 amp services will not see over 100 amps but once in a while.


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## mrcastrovinci (Jan 10, 2011)

Yeah i can see that but why not let me run my side 3 feet using the same size as the poco . Its only another three feet what changes between the line side of the meter and load side In 3 feet. Thats the part i dont get

Mr Castrovinci


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## BBQ (Nov 16, 2010)

It as Dennis said, the power company knows what works.


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## farlsincharge (Dec 31, 2010)

They can use 1/0 aluminum U/G for a 200 amp service here as long as it is under 30 metres.
It's bull ****


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## Rudeboy (Oct 6, 2009)

mrcastrovinci said:


> Yeah i can see that but why not let me run my side 3 feet using the same size as the poco . Its only another three feet what changes between the line side of the meter and load side In 3 feet. Thats the part i dont get
> 
> Mr Castrovinci


I don't disagree with your confusion but... you're an electrician, not a lineman. You have to follow the nec, really, and not worry about what the silly numbskulls at your local poco do.


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## mrcastrovinci (Jan 10, 2011)

Yeah they can do some crazy things while we still have to got to the letter of the code. Thats what baffels me 2/0 for them 4/0 for me. Not fighting it just wondering how it all came about the seperation of sizes between the line/load side of the meter. I wanted to make sure there was no exception to underground services that i have been missing.

Mr Castrovinci


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## piperunner (Aug 22, 2009)

Well just something you already know the wire we use is over sized per NEC .

But look at the wire in a freq drive or a motor or a factory made product like a UPS we run 500 mcm cu for a 400 amp inverter but the factory uses 1/0 cu and the 1/0 copper can handle 400 amps not in the NEC but it can hold it better insulation branded strands copper . 

Smaller wire can handle more current then what we see in the NEC .

Navy used number 10 wire number 13 wire number 15 wire there sizes were not standard sizes and 10 wire in the navy could run a 50 amp load not a issue theres a book i have on navy wire ill post the ampacity of some wire sizes .

Wire underground is in a different temp range wire in the air is cooler underground is cooler the poco doesnt go by our rules and they kinda know what is what there not just making it up .

They have it right were just using what were made to use because people are not controlled they add things after were done whos going to know what a owner will do later on down the road . So we give them that extra wire size to just be safer .


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## nitro71 (Sep 17, 2009)

Also would you rather the POCO's wire be the fuse or your wire? I'm pretty sure that's also part of it. Their wire should fail before our service entrance conductors do.


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## garfield (Jul 30, 2009)

A failure outside is an outage and one inside is a fire.


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## BBQ (Nov 16, 2010)

garfield said:


> A failure outside is an outage and one inside is a fire.


BINGO!:thumbsup:


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## BBQ (Nov 16, 2010)

nitro71 said:


> Also would you rather the POCO's wire be the fuse or your wire? I'm pretty sure that's also part of it. Their wire should fail before our service entrance conductors do.


BINGO again!


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## mrcastrovinci (Jan 10, 2011)

Excellant points guys. 


So very true and the ups is a great example I see that often with desiel locomototive cable or vfd wiring / factory devices.

I would have to agree with a failure occuring outside rather then inside.

Mr Castrovinci


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