240.86(C) - series combinations with motor contribution

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lielec11

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240.86(C) states that series ratings cannot be used where.... and then lists two conditions 1, and 2. Between 1 and 2 it says "and", so am I right to assume that BOTH of these need to be true for it to apply?

I am also a bit confused about 1, which states motors cannot be connected on the load side of the higher (protecting) breaker and on the line side of the lower (protected) breaker. How is that possible? If the motor is fed from the downstream (protected) panel, it will be on the load side of a breaker, not line side. What am I missing? The text in the Handbook doesn't really help me either.

2 seems fairly straightfoward in that the motor loads cannot exceed 1% of the interrupting rating of the lower rated circuit breaker but I have one question. Do I use the regular rating or the series rating? For instance if I have a 10k panel series rated for 65k, which rating do I take 1% of?
 
Think of multiple feeder breakers fed from a main breaker. The series rating would be between the main and one of the feeder breakers, but if any of the other feeder breakers supplied motor loads, that would trigger 240.86(C)(1).

It is my opinion, that (C)(2) applies to the actual rating of lower rated breaker.
 
So if I have a series rated panel with 20 loads, and 2 of them feed motors then we cannot apply a series rating? So basically any panel that serves motor loads cannot ever be series rated? That's how I'm interpreting this now based on your comment.
 
lielec11 said:
So if I have a series rated panel with 20 loads, and 2 of them feed motors then we cannot apply a series rating? So basically any panel that serves motor loads cannot ever be series rated? That's how I'm interpreting this now based on your comment.
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A series rated panel with 10,000AIC rated branch breakers would be able to be series rated if the motor load on the panel was a maximum of 100A.
This is a problem for series rating 'feeder' panels, but not much of a deal for most 'branch' panels with 100A and 200A bussing.
 
Are there any exceptions to 240.86(C) for motors on VFDs, non-coincident loads or other situations where connected motors have no fault current contribution?
 
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