400 amp electric utility meter

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400 amp meter 120/208V three phase what is the typical incoming electric utility feeder cable sizes? Need to size bonding jumpers and grounding electrode conductors.

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400 amp meter 120/208V three phase what is the typical incoming electric utility feeder cable sizes? Need to size bonding jumpers and grounding electrode conductors in service disconnect.



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Depends on some information.

NEC wise if you are supplying multiple service disconnecting means - the (common) conductors only need to be sized per load calculation. Conductors to an individual service disconnecting means need to be sized according to the overcurrent device - which if a single 400 amp device is all you have then you need 400 amp conductors. But you could have say 2- 250 amp overcurrent devices yet a total load calculation of only 325 amps - any service conductor that supplies both disconnects only needs to be a 325 amp conductor, which would include supply side of meter.

Now if you are asking what size conductor a utility company may install - it varies and is not based on NEC. I would quite often see 350 aluminum conductor (not paralleled, just one conductor per phase)used for this by a utility.
 
Not to mention that you say a 400 amp meter when actually you may be talking about a 320amp (continuous duty) meter. Usually at an actual 400amps service that would require a CT cabinet with CT meter.
 
codequestion said:
It says 400 amp meter on it?

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Self contained class 320 meter sockets are rated 320 amp continuous, 400 amps non continuous. Several utilities I work with dont allow them on commercial services - you need a CT cabinet for anything over 200. For a single 400 amp service disconnect, the conductors would need to be sized for the load and the "next standard size down" from the OCPD rating. This means you could have 351 amps of conductor if it met the load calc. Often times for small commercial services I will provide conductors with the full rating of the OCPD. I might do parallel 250 AL for a 400 depending on various things of course.
 
infinity said:
Look at 310.15(B)(16) and select a 400 amp conductor. Could be 500 kcmil copper if the calculated load is 380 amps or less.
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But jumpers and grounding electrode sizes changes per nec 2014 aricle 250 based on largest unground conductor. I am after bonding jumper sizes and grounding electrode conductor based on 400 amp electric utility meter 120/208V three phase.

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codequestion said:
It says 400 amp meter on it?

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Does the meter plug in or bolt in?

Plug in is what is called S base and is max 320 amps, bolt is K base can be 400 or 600 amps, though I have only seen about three or four of those in the wild, most POCO here are going to CT meter it if more then a 320 socket is necessary.
 
kwired said:
Does the meter plug in or bolt in?

Plug in is what is called S base and is max 320 amps, bolt is K base can be 400 or 600 amps, though I have only seen about three or four of those in the wild, most POCO here are going to CT meter it if more then a 320 socket is necessary.
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K base

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codequestion said:
K base

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So from what I can tell you are supplying a single 400 amp service disconnecting means from this meter?

That will mean minimum conductor size you can provide per NEC is 500 copper (provided load calculation is not over 380 amps), parallel 3/0 copper, 700 aluminum (provided load calculation is not over 375 amps), parallel 4/0 aluminum (provided load calculation is not over 360 amps).

As I mentioned earlier if utility is installing the conductor they may go smaller yet - many here would install 350 aluminum for a 400 amp service.
 
kwired said:
So from what I can tell you are supplying a single 400 amp service disconnecting means from this meter?

That will mean minimum conductor size you can provide per NEC is 500 copper (provided load calculation is not over 380 amps), parallel 3/0 copper, 700 aluminum (provided load calculation is not over 375 amps), parallel 4/0 aluminum (provided load calculation is not over 360 amps).

As I mentioned earlier if utility is installing the conductor they may go smaller yet - many here would install 350 aluminum for a 400 amp service.
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Utility go smaller? They dont do 500kcmil or 3/0 awg. My original question was to determine size of bonding jumpers and grounding electrode conductors. Does one look at feeder cables on the load side to service disconnect or on line side the utility feeder cables to determine grouding electrode conductor and bonding jumpers in service disconnect?

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codequestion said:
Utility go smaller? They dont do 500kcmil or 3/0 awg. My original question was to determine size of bonding jumpers and grounding electrode conductors. Does one look at feeder cables on the load side to service disconnect or on line side the utility feeder cables to determine grouding electrode conductor and bonding jumpers in service disconnect?

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GEC - look at heading in T250.66, it says "size of largest ungrounded service conductor or equivalent area for parallel conductors".

250.102 table says same thing but is missing the word "service".

I think if you are landing the conductor/bonding jumper in the meter you go by supply side conductor if they are different from load side conductor. If you are landing the conductor/bonding juper in the service disconnecting means - you go by the conductors that are between meter and service disconnect even if supply side of meter is different.
 
kwired said:
So from what I can tell you are supplying a single 400 amp service disconnecting means from this meter?

That will mean minimum conductor size you can provide per NEC is 500 copper (provided load calculation is not over 380 amps), parallel 3/0 copper, 700 aluminum (provided load calculation is not over 375 amps), parallel 4/0 aluminum (provided load calculation is not over 360 amps).

As I mentioned earlier if utility is installing the conductor they may go smaller yet - many here would install 350 aluminum for a 400 amp service.
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Now going back, the utility would provide 350kcmil for 400 amp k base meter assuming it is 400 amp service? Utility would not provide 500 kcmil or 2 sets of 3/0 awg?

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codequestion said:
Now going back, the utility would provide 350kcmil for 400 amp k base meter assuming it is 400 amp service? Utility would not provide 500 kcmil or 2 sets of 3/0 awg?

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But if you install conductors between meter an service disconnect - you inspector is going to fail if you ran 350 because you must follow NEC, even though logic tells you 350 is probably not going to overheat if it will works for them on the supply side of meter. So now you have 500 or parallel 3/0 for service entrance conductors if you are running GEC to the service disconnect.
 
kwired said:
But if you install conductors between meter an service disconnect - you inspector is going to fail if you ran 350 because you must follow NEC, even though logic tells you 350 is probably not going to overheat if it will works for them on the supply side of meter. So now you have 500 or parallel 3/0 for service entrance conductors if you are running GEC to the service disconnect.
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Correct. I was talking about conductors from utility transformer to utility meter. I am also calculating short circuit fault at service disconnect and was wondering typical conductor size electric utility would install for 120/208V 3 phase 400 amps base k meter. Assuming thats 400 amps service.


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codequestion said:
But jumpers and grounding electrode sizes changes per nec 2014 aricle 250 based on largest unground conductor. I am after bonding jumper sizes and grounding electrode conductor based on 400 amp electric utility meter 120/208V three phase.

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see 250.66 250.102(C)(1). You are going to have to nail down the conductor size before you will know what GEC size you will need.

Edit: sorry this was already covered. I missed the whole second page of posts.
 
codequestion said:
Correct. I was talking about conductors from utility transformer to utility meter. I am also calculating short circuit fault at service disconnect and was wondering typical conductor size electric utility would install for 120/208V 3 phase 400 amps base k meter. Assuming thats 400 amps service.


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350 aluminum seems to be common, but why not ask the utility in question?
 
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