NEC vs NFPA

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sheffield

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I'm a controls engineer. I design control panels and do PLC programming for machinery and conveyor systems. My question is which do I use? My thoughts would be that I would use NFPA 79, ELECTRICAL STANDARD FOR INDUSTRIAL MACHINERY rather than the NEC. The NEC seems like it's more for building wiring instead of the machine wiring.

Thanks,
Barry
 
Re: NEC vs NFPA

Barry,

IMO it would be NFPA 79, as that is the standard for machinery that makes things. I use NEC because our equipment does not make things. Maybe I'm over simplifying?? I personally would not use both.

Tony
 
Re: NEC vs NFPA

I think in all reality, you will have to use both. The NEC will cover issues such as what methods and materials can be used to serve the equipment, and the NFPA 79 standard will cover the specifics of the equipment.

I am not familiar with the NFPA 79 standard, but I am sure it references the NEC when apllicable.
 
Re: NEC vs NFPA

If you follow NFPA79 then you must also follow NFPA70, it is not a case of either or. In regards to industrial machinery as defined in NFPA70, Art 670 says the NEC only covers the supply to the machinery.


From NFPA79 2002

1.4.1 says the supply conductors to the machine are covered by the NEC. Also wiring between machines is subject to the NEC.

1.5 says that if it is not covered by NFPA79 then the NEC shall be followed.

Chapter 2 lists documents which shall be considered parts of NFPA79 and 2.2 is NFPA70
 
Re: NEC vs NFPA

As an electrical designer of packaging machinery, I use both. I view NFPA79 as a supplement to the NEC that has special considerations for machinery, some more restrictive and others less restrictive. When the NEC addresses an item but NFPA79 does not, I adhere to the NEC.

Depending on where you are located, there can be other codes that apply. For example, if machinery will be installed in Minnesota and other locations such as Chicago, UL is very much referenced. We are also asked to do our best to meet the requirements for OSHA however, we are not held responsible for compliance. This is left up to the end-users.

For non-domestic end-users we will adhere to their specific codes such as CGSC (Capitol Goods Standard Coalition) using the CE mark in Europe and the CSA standards in Canada.

Bob
 
Re: NEC vs NFPA

The reason I brought up this was due to a company inspector using the code referring to TC Cable. We're using TS cable (SOOW) running from junction boxes out to a Din connector that goes on a solenoid valve (24VDC). The inspector is stating that we're supposed to have that cable run in conduit. We're stating that it doesn't per NFPA 79 (14.1.4.1) & (14.1.5.1).

This inspector is also stating that the NFPA cannot be used. Only the NEC. The last time I checked, the NEC is NFPA 70. Therefore it is NFPA.

Thanks,
Barry
 
Re: NEC vs NFPA

Shefflied,

We are in the same business and run into this all the time. If the wiring methods you are speaking of are attached to the building, then apply NFPA 70. If they are part of or are attached only to the machinery, then apply NFPA 79.

For example, the feeders to a floor mounted control panel that originate at a bus plug mounted in the trusses is covered by the NEC. Wiring in trenches is NEC. The panel is NFPA 79. Cables run in trays from the panel, that are supspended from the trusses are also NEC since they are attached to the building. Cables and cords distributing I/O and control circuits on the machine are not NEC but NFPA 79.

Does this help?
 
Re: NEC vs NFPA

I agree with you. It is our understanding that NFPA79 comes into play after our machine's main disconnect switch. It gets a little blurry when the main disconnect enclosure is located in a remote location off the machine frame. In this case, it has been my understanding that the cable tray or conduit between the enclosure and the machine are NEC.

Bob
 
Re: NEC vs NFPA

In my opinion, NFPA 79 is useless. It conflicts with the NEC (i.e. 'color codes) and is inadequate in many other ways.

Unlike the NEC, I have yet to encounter a jurisdiction that has adopted 79. That's why your AHJ doesn't use it.

Another body that studiously shuns 79 is UL. I suggest that anyone involved in the design or manufacture of control equipment invest in the appropriate UL standards. Moreover, such things are typically manufactured in listed "panel shops."

The 2005 NEC may, or may not, have a section dealing with control panels.

That said, I am not aware of any general standard that addresses how a control panel operates. Even the most code-compliant equipment can be told to operate in an unsafe manner.
 
Re: NEC vs NFPA

The lines are not blurry here. Any electrical wiring that is contained within a piece of equipment listed by a qualified testing laboratory is not subject to the NEC. Check out 90.7.

If someone field designs and assembles and wires some electrical equipment, said equipment is subject to all the rules of the NEC.

If someone designs and builds the same equipment off-site, then has the equipment evaluated by an approved testing lab (Factory Mutual, UL, etc.), then the equipment is not subject to the NEC, but the hookup and any field wiring is.

If someone designs and builds the same equipment in the field, and has the approved testing lab come out and certify that it is safe, the BO can accept this as well.

NFPA 79 is an excellent standard for designing the equipment, but it is not building code. The inspector can only inspect to the building code. Give him a handle to use. Give him the FM seal of approval. (or UL or CSA, or etc.) But, all building field wiring must comply with the NEC.

Earl
 
Re: NEC vs NFPA

Thanks to all of you that agreed with the NFPA 79. For those of you that didn't, I spoke directly to Joseph Sheehan, the NFPA staff liason at NFPA headquarters. I told him what I had problems with and he told me that by using NFPA 79, I was following the proper practice. He aslo told me that for the most part, NEC is designed for construction/building wiring. He aslo referred me to NFPA 70, Article 670 in the NEC. By the way, Joseph Sheehan is also the Senior Editor for the NEC-2002 Handbook.

Thanks!
 
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