# Article 409



## rwilsond (Jun 25, 2007)

A particular 480V Industrial Control Panel in a "Supervised Industrial Installation" is fed from a large (say 2000 kVA) transformer, without any type of OCPD on the transformer's secondary side, and without a Main CB inside the panel. Instead, the 15-foot long tapped supply conductors terminate onto two separate CB's inside the control panel.

New Article 409 for the 2005 NEC requires that either a single OCPD be located ahead of an Industrial Control Panel, or a Main CB (i.e., ONE CB) be located within the Industrial Control Panel. But 409.21 states that this protection shall be provided in accordance with 240.21 Parts I, II, and IX. 

Can the reference above (to 240.21) be interpreted to mean that the Industrial Control Panel is allowed to NOT have a Main CB (Main implies ONE), nor an upstream feeder CB by satisfying one of the tap-rules of 240.21?


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## raider1 (Jan 22, 2007)

The only way you can have the secondary conductors of a transformer not protected by an overcurrent device on the secondary side is to comply with 240.21(C)(1).

Chris


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## rwilsond (Jun 25, 2007)

Why do you say 240.21(C)(1)? It appears to me that I could use any one of the six sub-sections of 240.21(C), except (2) and possibly (5).

But the question I asked has more to do with the Industrial Control Panel requirement in Article 409 that an OCPD be provided ahead of the panel, or a MCB inside of the panel, and the reference to 240.21 that appears under 409.21(A).


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## raider1 (Jan 22, 2007)

409.21(A) requires that an industrical control panel have overcurrent protection in accordance with Parts I, II, and IX of Article 240.

409.21(B) requires that you provide either;

1. An overcurrent device located ahead of the industrial control panel or;

2. A single main overcurrent device located within the industrial control panel. Where overcurrent protection is provided as part of the industrial control panel, the supply conductors shall be considered as either feeders or taps as covered by 240.21.

So according to this section you must have a single overcurrent device in the industrial control panel or a overcurrent device ahead of the control panel.

The reason that I quoted 240.21(C)(1) was that this is the only section that allows the primary overcurrent device of a transformer to be the only protection on the secondary side of a transformer. I missed the part where you said you had two breakers in the control panel.

Chris


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## Joe Tedesco (Mar 25, 2007)

*See this*

http://www.nfpa.org/displayContent.asp?categoryID=1024


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