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#168009 - 08/25/07 08:57 AM Is this 13.8 feeder legal?
windmiller Offline
Junior Member

Registered: 12/05/06
Posts: 43
Loc: Alaska
Hi,
I need some advice on a long 13.8 feeder that comes from a breaker to several underground MPC's.. (Mine Power Center) this is a vacuum breaker at the MPC. The MPC is basically a transformer that steps down from 13.8kV to 480V with 225A instantaneous trip breakers. There is a window on the MPC unit to view the switch inside. The main breaker (that feeds the first MPC in the group will not close unless the switch at the MPC is closed. There is a feed through setup on the line side of the MPC. From there another feeder is terminated on the line side feed through connectors then runs down about a 1000 feet to another MPC, then to another and another and another. 240.21 Says that a circuit must have OCP at the point where it receives its supply. An engineer is saying that this is allowed by 240.21(C)(2).

I think he is mistaken.

I and the other electricians here think that there needs to be OCPD at point where the circuit receives its supply. Is there a tap rule that would allow this?

MSHA says this needs a disconnect. Please see http://www.msha.gov/30CFR/0.0.htm

Thank you for any responses.

windmiller
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#168011 - 08/25/07 09:23 AM Re: Is this 13.8 feeder legal? [Re: windmiller]
windmiller Offline
Junior Member

Registered: 12/05/06
Posts: 43
Loc: Alaska
Additional information:

The 13.8kV vacuum circuit breaker has a line side disconnect. It is a "packaged" interlocked installation. Opening the disconnect while the breaker is closed will trip the breaker prior to the disconnect blades opening. In addition closing of the circuit breaker is not possible unless the it's integral line side disconnect is closed.

there is a viewing window on all disconnects to ensure that these disconnect blades have actually opened when the disconnect operating handle has been operated. This is required by MSHA 30 CFR § 56.12006.
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#168019 - 08/25/07 01:02 PM Re: Is this 13.8 feeder legal? [Re: windmiller]
windmiller Offline
Junior Member

Registered: 12/05/06
Posts: 43
Loc: Alaska
There is a sectionalizing compartment in the MPC so I would say that this is not a distribution box but rather a Splice or J-box.

So this should comply with the NEC.

Thanks

Windmiller
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#168048 - 08/26/07 04:06 AM Re: Is this 13.8 feeder legal? [Re: windmiller]
Tom Offline
Member

Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
The NEC does not apply to this installation, see 90.2(B)(2)
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#168070 - 08/26/07 12:23 PM Re: Is this 13.8 feeder legal? [Re: Tom]
windmiller Offline
Junior Member

Registered: 12/05/06
Posts: 43
Loc: Alaska
Tom,
I appreciate your response but I must disagree. The article says it does not "COVER" it.

MSHA says:
At metal and non metal surface and underground mines the Mine Safety and Health Administration (MSHA) does not specifically enforce the National Electric Code (NEC). MSHA does use the NEC as a reference source. If your operation is in compliance with the provisions of the NEC, your operation will be in compliance with the MSHA standards addressing the same matters.

For metal and non metal surface and underground mines the standards dealing with over current protection can be found in Title 30 Code of Federal Regulations (30CFR) Subpart K – Electricity. Standards 30 CFR § 56/57.12001, 56/57.12002 and 56/57.12004 address over current protection.

For you reference and review below is a link to 30 CFR.
http://www.msha.gov/30CFR/0.0.htm
-------------------------

That said, we try to meet both MSHA and the NEC. You cant be an electrician and not use the NEC in my opinion. Industry standards is the key word here. Just because the NEC does not cover it does not mean I cant use it to install safely.

This installation actually does meet the NEC. The real question is 240.21. This is a continuous conductor that does receive its supply from a OCPD. The MPC has a Splice/Jbox built into it with barriers and firewalls to protect it from the other components.

Thanks

Windmiller
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#168138 - 08/27/07 05:00 PM Re: Is this 13.8 feeder legal? [Re: windmiller]
George Little Offline
Member

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
Look at the scope of 240 and you'll see that 220.21 does not apply to over 600v.
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#168141 - 08/27/07 05:20 PM Re: Is this 13.8 feeder legal? [Re: George Little]
windmiller Offline
Junior Member

Registered: 12/05/06
Posts: 43
Loc: Alaska
George,
220.21 does not exist. Did you mean 240.21?

thanks

Windmiller
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#168142 - 08/27/07 05:21 PM Re: Is this 13.8 feeder legal? [Re: windmiller]
George Little Offline
Member

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
Yes Windmiler- that was a test \:\)
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