NEC 240.86 Series Ratings?

[chuck@apsinc.biz]

Re: NEC 240.86 Series Ratings?

All,

I got with the local utility and found that the available fault current on the primary side of the service transformer was 1,300 amps at 14.4KV.

That put my available on the secondary side(not including motor contribution) at 17,400AMPS.

Considering 4,000 amps of motor contribution and routing the feeder to the VFD so it's length was extended to 50LF I was able to get the available fault current at the VFD below the VFD's rating of 18,000 AMPS.

Thanks to all for the input. It certainly provided the best solution for my clients issues.

 

[gwz2]

Re: NEC 240.86 Series Ratings?

So you've got a solution, great !


Had a similar installation several years ago where the original installer installed an extra 40 feet of feeder to a 60 Amp ( 10 Kaic, withstand rating ) contactor next to MDP, which supplied a panel by control of a timer. This was when the building was built.

About 3 years later some additions was made to the building and additional electrical work at the MDP.

The 'New' electrical contractor seeing that 40 feet of raceway and conductor took it upon himself to replace that 40' of conductor with about 3.5' of conductor, thus, violation of the 'withstand rating' of the contactor.

My boss, in all his wisdom, refused to accept my rejection of the alteration.

"If the sytems works when applying the power, it must be wired right. "

I assume it is still that way today, since I was 're-tired' by that city shortly afterwards.

[ October 10, 2003, 03:09 PM: Message edited by: gwz2 ]