I am working with a panel that has a motor control unit as well as an opto rack and three different voltages in it. I am almost positive this is not allowed but I have not been able to identify what is proper in the NEC code book. I have 480 three phase entering the panel running a motor drive, then going to an 30 amp breaker and on to a dropping transformer. This is dropping me down to 120 volt. This then proceeds to the opto rack which is controlled by an entirely different supplied 5vdc circuit. Can somebody point me in the right direction in the 2005 NEC Code book for guidence?
Panel code
- Thread starter Grace
- Start date
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peter d
Senior Member
- Location
- New England
Re: Panel code
The NEC doesn't cover factory made listed equipment. Well, at least it's not supposed to. Vending machines are one exception. :roll:
The NEC doesn't cover factory made listed equipment. Well, at least it's not supposed to. Vending machines are one exception. :roll:
peter d
Senior Member
- Location
- New England
Re: Panel code
Yes, what you describe is the norm for industrial control panels and equipment.
Yes, what you describe is the norm for industrial control panels and equipment.
peter d
Senior Member
- Location
- New England
Re: Panel code
Hold on a sec....I am now remembering some NEC articles that might apply, but I've misplaced my code book.
Stay tuned, others will weigh in.
Hold on a sec....I am now remembering some NEC articles that might apply, but I've misplaced my code book.
Stay tuned, others will weigh in.
peteo
Senior Member
- Location
- Los Angeles
Re: Panel code
Leading question here. I don't know whether this is an article 430.92 MCC, 670 industrial machinery, or what. Typically, 670 covers equipment which is manufactured with a nameplate, as opposed to field built panels. What was a new '670 requirement and implemented in 1999 (here, at least,) were SCCR requirements. The 2005 NEC seems to have applied those rules to anything with "two or more components" with the new article 409.
Leading question here. I don't know whether this is an article 430.92 MCC, 670 industrial machinery, or what. Typically, 670 covers equipment which is manufactured with a nameplate, as opposed to field built panels. What was a new '670 requirement and implemented in 1999 (here, at least,) were SCCR requirements. The 2005 NEC seems to have applied those rules to anything with "two or more components" with the new article 409.
Re: Panel code
In article 409 of the NEC 2005 I still don't see where it says anything about mixed voltages in the same panel. Basically, if I am reading this correctly it refers me to table 409.3 then to article 430 and so and so forth but still is not clear. Am I looking for something in black and white that I will not find? :roll: Typical of my life.....
[ March 01, 2006, 02:07 PM: Message edited by: Grace ]
In article 409 of the NEC 2005 I still don't see where it says anything about mixed voltages in the same panel. Basically, if I am reading this correctly it refers me to table 409.3 then to article 430 and so and so forth but still is not clear. Am I looking for something in black and white that I will not find? :roll: Typical of my life.....
[ March 01, 2006, 02:07 PM: Message edited by: Grace ]
peteo
Senior Member
- Location
- Los Angeles
Re: Panel code
Sorry about that. You asked about inspection, and (here anyway) an inspector would expect a testing label on the product. I threw the label issue (article 409) into the pot. Ignore that for now.
My real question was, are you assembling this panel? The definition for motor control center is in article 100. MCCs are in chaper 4, General Use Equipment. The definition of industrial machinery is in article 670.2, which would scope it within chapter 6 Special Equipment. The individual parts inside your panel (wire duct, transformers, etc.) will have similar requirements in any case. As a general result, following article 670 rules will work. But then, you'll need to refer to the 'expanded' version, which means a separate publication, NFPA 79. You probably will not find all the rules for industrial equipment in the regular NEC.
Sorry about that. You asked about inspection, and (here anyway) an inspector would expect a testing label on the product. I threw the label issue (article 409) into the pot. Ignore that for now.
My real question was, are you assembling this panel? The definition for motor control center is in article 100. MCCs are in chaper 4, General Use Equipment. The definition of industrial machinery is in article 670.2, which would scope it within chapter 6 Special Equipment. The individual parts inside your panel (wire duct, transformers, etc.) will have similar requirements in any case. As a general result, following article 670 rules will work. But then, you'll need to refer to the 'expanded' version, which means a separate publication, NFPA 79. You probably will not find all the rules for industrial equipment in the regular NEC.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: Panel code
As much as you would like (or expect)it to the NEC is not directly applicable to the inside of control cabinets.
90.7 does not require equipment to be "listed". it just says it makes the AHJs job easier.
Article 409 basically says to follow the other sections of the code in regards to overcurrent protection and conductor sizing for the feeds supplying the panel.
430.91 does almost the same thing for motor control centers, it is primarily concerned with the supply to the equipment.
670.1 specifically says it only cares about the supply conductors.
Your best hope for the issue of multiple voltages in close proximity is article 725. But, 725.1 states it is not applicable to circuits integral to devices.
Instead do what the FPN to 409.1 says, look at UL508A. And, I would add, NFPA79 Standard for Industrial Equipment.
As much as you would like (or expect)it to the NEC is not directly applicable to the inside of control cabinets.
90.7 does not require equipment to be "listed". it just says it makes the AHJs job easier.
Article 409 basically says to follow the other sections of the code in regards to overcurrent protection and conductor sizing for the feeds supplying the panel.
430.91 does almost the same thing for motor control centers, it is primarily concerned with the supply to the equipment.
670.1 specifically says it only cares about the supply conductors.
Your best hope for the issue of multiple voltages in close proximity is article 725. But, 725.1 states it is not applicable to circuits integral to devices.
Instead do what the FPN to 409.1 says, look at UL508A. And, I would add, NFPA79 Standard for Industrial Equipment.
Re: Panel code
Contrary to what most people would like to believe there is no code restricion against mixing voltages in equipment or even conduit. The insulation must be suitable for the highest voltage available and there is a restriction for adjacent terminals which have over 300 volts difference between them. Other than that, nothing else comes to mind, but I don't have a book available right now.
Contrary to what most people would like to believe there is no code restricion against mixing voltages in equipment or even conduit. The insulation must be suitable for the highest voltage available and there is a restriction for adjacent terminals which have over 300 volts difference between them. Other than that, nothing else comes to mind, but I don't have a book available right now.
peter d
Senior Member
- Location
- New England
Re: Panel code
That is true, but the requirements of 725.52. 725.54 and 725.55 etc must also be followed.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: Panel code
725 only covers class 1-2-3 circuits.
peter d said:
725 only covers class 1-2-3 circuits.
peter d
Senior Member
- Location
- New England
And your point is?
Grace,I think the permission to allow different voltages comes from 430.72.These are control circuits,and the protection for these circuits come from within the enclosure.Where these circuits originate from other sources,protection comes from 725.23 or the notes to table 11(A) and table 11(B) in chapter 9.Also in 725.26(B)1 and 2.and if these other circuits are class 2-3 then 725.55 applies where seperated in the enclosure.
Rick
Rick
- Location
- Illinois
- Occupation
- retired electrician
Bob,
Don
Otherwise known as control circuits.
Don
- Status