Conductors of Different Systems

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Jim Giefer

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We are currently working on a water treatment plant. The engineer's design consisted of installing controls wire (120v- for remote HOA) with the power wires (480v) in the same conduit to the motor's local disconnecting means.

When we roughed-in the conduits we used common pull boxes. Example: 4 - 3/4" GRC W/3-#12 THHN & 1-#12 GR (motor) & 4-#14 THHN (remote HOA). These conduits & wires share the same pull box/enclosure.

The Engineer told us according to NEC 725.26 (B) (1); "Class 1 circuits and power supply circuits shall be permitted to occupy the same cable, enclosure,or raceway only where the equipment powered is functionally associated". So we were not meeting code because the motors wires feed different pumps that are not functionally associated.

I said according to NEC 303.3 (C) (1) we comply with NEC and Chapter 7 is for special conditions that do not apply to this work. The engineer said that later chapters in the NEC supersede the lower chapters.

My questions:
1.) Given the information above are we in compliance with the NEC?
2.) Do later chapters in the NEC supersede lower chapters?

Please give explanation

Thanks

Jim Giefer
 
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Jim,
I tend to agree with the engineer, but some will say that the motor control circuits are covered by Article 430, not 725. It is my opinion that motor control circuits are coverd by both.
2.) Do later chapters in the NEC supersede lower chapters?
Click to expand...
Yes they do. Look at the last part of 90.3.
90.3 ... Chapters 1 through 4 apply except as amended by Chapters 5, 6, and 7 for the particular conditions.
Click to expand...

Don
 
Don,

It depends. If the motor control circuit transformer is rated over 1000VA then Article 725 does not apply. Reference Section 430.72(C)(1).
 
RB,
I don't agree. That section does not cover anything other than the overcurrent protection of the secondary conductors. It does not say that the other rules in 725 do not apply to motor control circuits.
Don
 
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