Parralel riser conductors

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kiss

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I am planing to run 2 sets of 350MCM THWN wire as a riser, with pull boxes on each floor from a 600Amp switch in the basement.
I would like to tap on each floor to a 3phase 4wire panel rated at 100Amps
with a main breaker panel.
What is the proper way to tap these risers??
We have debated this on the job over the last few days and no one can back up their argument with any code section including me.
All input is appreciated
 
kiss said:
What is the proper way to tap these risers??
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There are many ways but what exactly are you asking about?

The fact your trying to tap parallel sets with a single set makes it a pain.

You will need to tap both conductors of each phase on each floor.
 
O.K. The panels will be about 15 feet away from the pull box, all wiring is copper. I am thinking of tapping 1 set of risers with # 3THWN to feed my 100Amp panel that will have a main breaker on the 1st floor. Tapping the 2 set of risers with #3THWN as above on the next floor, and alternating taps on each floor evenly. Possible doing 3 floors with each set. Is this allowed as per NEC and if not where can I find it.
 
kiss said:
Possible doing 3 floors with each set. Is this allowed as per NEC and if not where can I find it.
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I would say no. Parallel conductors need to terminate together at each tap. Look at 310.4.

Also since you're using copper conductors you will need to provide conductor support for every 60' of vertical riser. Look at Table 300.19(A).
 
kiss said:
I am planing to run 2 sets of 350MCM THWN wire as a riser, with pull boxes on each floor from a 600Amp switch in the basement.
I would like to tap on each floor to a 3phase 4wire panel rated at 100Amps

All input is appreciated
Click to expand...


Which tap rule do you intend on following??? From 600 amps down to 100 amps is a lot, and you already mention the taps are more than 10 feet.
 
I would follow which ever tap rule applies. The problem I have,is that I do not have room in the basement to install 2 seperate 400Amp disconects being fed from my 600 amp distribution panel. That's why I was thinking parralel sets and taping of to 100Amp panels with main circuit breakers. Any suggestions??
 
If the 600Amp feed thru panel is as big or bigger than a 400Amp commercial panel, I don't have the space. This job is in an existing space with limited space.
 
What about, instead of a single 600a switch, use two separate 300a (or even 200a if loads allow it) breakers in a single cabinet for the two sets of conductors, and don't parallel them.

Tap rules allow supplying three 100a panels from each conductor set, with up to 25' feeder length with not less than 1/3 the feederss supply OCPD's, which is why I suggest two 300a breakers.
 
You could look at busduct for the riser and a 100amp plug in breaker at each floor and MLO panels.
Don
 
LarryFine said:
What about, instead of a single 600a switch, use two separate 300a (or even 200a if loads allow it) breakers in a single cabinet for the two sets of conductors, and don't parallel them.

Tap rules allow supplying three 100a panels from each conductor set, with up to 25' feeder length with not less than 1/3 the feederss supply OCPD's, which is why I suggest two 300a breakers.
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Thinking along the same line as Larry - I was wondering what is the actual load on these 100A panels on each floor? Is it possible 400A will supply the actual load for these six 100A panels?
 
Thanks for all the suggestions. Problems on the job are many!! Existing service has 5 mains. No room to rip out existing, and install 1 main and new distribution panel. I only have room to add 1 more switch for a total of 6 mains. I may have to install an 800 amp main and feed 2 -400amp switches.
Then run 1 set 500MCM from each 400 to feed 4-5 floors and tap at each floor with a 100amp panel with a main breaker. Any suggestions are welcome.
 
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