switchboard

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bwyllie

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MA
Is this a problem, a 1600A service is installed to a 4-section switchboard w/ 6 throws of the hand, the first section is the pull section rated 1600A, the second section is rated 1600A supply, the third section 1000A supply and fourth section rated 1600A supply.

Question is should the third section be rated 1600A supply?

Thank you
 
Re: switchboard

So the 1000 amp third section is feeding the 1600 amp fourth section?
 
Re: switchboard

The name plate for the third section listed the supply as 1000A, section as 1000A. I am not sure of the exact configuration of the supply busses through all the switchboards.
 
Re: switchboard

Off the top of my head I would say it means little.

As you are using the 'six throws of the hand' for your service disconnects the service conductors (in this case including the buss bars) only need to be rated for the load they will carry, not the total of the six switches.


230.90 Exception No. 3: Two to six circuit breakers or sets of fuses shall be permitted as the overcurrent device to provide the overload protection. The sum of the ratings of the circuit breakers or fuses shall be permitted to exceed the ampacity of the service conductors, provided the calculated load does not exceed the ampacity of the service conductors.
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Re: switchboard

Usually with the type of gear sectioins that I have seen, there are one set of bars going across the back of the gear feeding all of the sections. then there are bars feeding each individual section.

the individual section may be feed at one rating, but the feed through may be the full load for the entire gear.

I cant say that is what you have, but that is what i have seen in the past.
 
Re: switchboard

In this set up the buss bars really do not have overcurrent protection.

If the bus bars are rated 100, 1000 or 2000 amps the utility will provide enough current to melt them down. :D

The only protection these bus bars have is accurate load calculations.

It seems possible that the third and forth sections do not have enough calculated load to need more than a 1000 amp mid section.

Or

For reasons unknown the EC put them together in the wrong order, perhaps to make the buckets fall in better locations to their raceways.

I have also seen what JB mentioned, 1,600 feed through 1000 amps per section.

[ December 29, 2005, 05:20 PM: Message edited by: iwire ]
 
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