ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

ECN Shout Chat
Top Posters(30 Days)
Admin 16
Recent Posts
ESA Arc flash course
by TheShockDoctors. 03/24/17 10:15 AM
fuse rejectors
by HotLine1. 03/24/17 07:53 AM
Another Forum Update
by Admin. 03/22/17 03:04 PM
Dining room plugs
by watersparkfalls. 03/21/17 10:31 PM
TRUE POWER
by jraef. 03/21/17 09:13 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
231,340 Are you busy
166,077 Re: Forum
160,541 Need opinion
Who's Online Now
0 registered members (), 82 guests, and 12 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#168009 - 08/25/07 11:57 AM Is this 13.8 feeder legal?  
windmiller  Offline
Junior Member
Joined: Dec 2006
Posts: 43
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


We all live under one King

2017 / 2014 NEC & Related Books and Study Guides

#168011 - 08/25/07 12:23 PM Re: Is this 13.8 feeder legal? [Re: windmiller]  
windmiller  Offline
Junior Member
Joined: Dec 2006
Posts: 43
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.


We all live under one King

#168019 - 08/25/07 04:02 PM Re: Is this 13.8 feeder legal? [Re: windmiller]  
windmiller  Offline
Junior Member
Joined: Dec 2006
Posts: 43
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


We all live under one King

#168048 - 08/26/07 07:06 AM Re: Is this 13.8 feeder legal? [Re: windmiller]  
Tom  Offline
Member
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
The NEC does not apply to this installation, see 90.2(B)(2)


Few things are harder to put up with than the annoyance of a good example.

#168070 - 08/26/07 03:23 PM Re: Is this 13.8 feeder legal? [Re: Tom]  
windmiller  Offline
Junior Member
Joined: Dec 2006
Posts: 43
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


We all live under one King

#168138 - 08/27/07 08:00 PM Re: Is this 13.8 feeder legal? [Re: windmiller]  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Look at the scope of 240 and you'll see that 220.21 does not apply to over 600v.


George Little

#168141 - 08/27/07 08:20 PM Re: Is this 13.8 feeder legal? [Re: George Little]  
windmiller  Offline
Junior Member
Joined: Dec 2006
Posts: 43
Alaska
George,
220.21 does not exist. Did you mean 240.21?

thanks

Windmiller


We all live under one King

#168142 - 08/27/07 08:21 PM Re: Is this 13.8 feeder legal? [Re: windmiller]  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Yes Windmiler- that was a test smile


George Little


Member Spotlight
renosteinke
renosteinke
Blue Collar Country
Posts: 5,316
Joined: January 2005
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.017s Queries: 15 (0.003s) Memory: 0.7921 MB (Peak: 0.9550 MB) Zlib enabled. Server Time: 2017-03-24 19:55:47 UTC