240.21 help

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shockare

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I need some help on 240.21(b)1 or (b)2 ?

Working on a remodel of a local restaurant. Plans call for a new 225 lighting panel. MDP at 6 throws already.

So Installed a new 600 main breaker feeding parallel 350s. to the trough
where i taped with 3 awg to 3 new nema 1 dead fronts.

In the dead fronts i used the salvaged (225) (175) and new (225) feeder breakers. fist 2 no problem nippled to the trough

With space very tight i needed to install the last dead front aprox. 14 feet (wire length ) away for the feeder tap

Question is does this last tap comply with 240.21 b 2 ?
 
I would help if you explained the feeder diagram a little better. It sounds like you tapped # 3awg from the parallel 350 kcmil to go to each of the 175, 225, and the new 225 panels.
 
The 3/o conductors meet the 25' tap rule, but the ocpd is not matched to the conductor size. tap conductors have to be protected at or below the ampacity.With 3/0, your maximum ocpd should be 200 amps. you need to go with 4/0cu. for the 225 amp breakers. If you are using parallel 3/0 conductors, then you would be ok.
Rick
 
meets basic Code language.
the "devil is in the details" as to whether it meets Code (method of tapping, etc)
 
augie47 said:
meets basic Code language.
the "devil is in the details" as to whether it meets Code (method of tapping, etc)
Click to expand...

if he only used 3/0 cu., 240.21 (B)1 and (B)2 requires the conuctors to be protected at or below their ampacity. The 225 breakers are to big.
Rick
 
agreed, I read your answer and thought I had modified mine to reflect your point. My edit didn't make it..
You are definitely correct and it only appears that I disagree due to my lack of computer skills.:smile:
 
thanks for info

thanks for info

I was looking at 310.16 table 90* column

3/0 at 90* is good for 225 My calculated load at the new lighting panel
is nom. 75.4 kw
 
shockare said:
I was looking at 310.16 table 90* column

3/0 at 90* is good for 225 My calculated load at the new lighting panel
is nom. 75.4 kw
Click to expand...

Unless you are calculating derating factors, there's no need to even look at the 90? column. See 110.14(C)(1).
In all probabilty your install is limited to the 75? ratings.

also if your load is continuous (3 hrs or more) I believe your panel is undersized.
 
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