Design Reference Sources (NFPA, NEC Codes & Standards)

Thread Starter

maitrey

Joined Sep 4, 2014
72
Hello All,

I am a young professional electrical engineer who has just started working in Automation field. We build customized panels including PLCs, HMIs, Pushbuttons, Lights, Relays etc., I have been searching for a reference codes and standards that can be helpful for designing and wiring panels. I have already came across NFPA 79, UL and NRTL standards but it's just overwhelming at this point. I am confused on which book or standards to start with. Can you guys recommend me resources/books/articles that I must consider?

Let's discuss in the thread :)

Thanks,
Mac
 

MaxHeadRoom

Joined Jul 18, 2013
23,658
What part is overwhelming?
NFPA79 lays most of it out.
I would get accustomed to using DIN rail mount components, also Ducting such as Panduct etc to keep wiring neat, and to keep ducting size down using wire with thinner insulation, but still rated 250v, check out using TR64 cabling.
Also search panel building here for previous threads, e.g. https://forum.allaboutcircuits.com/...-router-controls-cabinet.173344/#post-1558534
Max.
 

Thread Starter

maitrey

Joined Sep 4, 2014
72
NFPA articles also refer to IEC-60204, IEC-61508 etc., I am not sure what are these references? I don't think NFPA book refers to using ESR relay to electromechanically disconnect all devices in circuit. Am I missing something here?
 

Papabravo

Joined Feb 24, 2006
16,840
Standards are carefully written to AVOID the specification of parts from a particular manufacturer. They are written instead as a set of requirements that particular parts may or may not meet. Your job as a junior engineer is to become familiar with the requirements, so you can offer your professional opinion on whether a particular part or method of installation meets or does not meet the appropriate standard. At least that was the way we tried to do it when I worked on a standards committee.
 

Thread Starter

maitrey

Joined Sep 4, 2014
72
Standards are carefully written to AVOID the specification of parts from a particular manufacturer. They are written instead as a set of requirements that particular parts may or may not meet. Your job as a junior engineer is to become familiar with the requirements, so you can offer your professional opinion on whether a particular part or method of installation meets or does not meet the appropriate standard. At least that was the way we tried to do it when I worked on a standards committee.
What standards are more common which I should get familiar with first?
 

MaxHeadRoom

Joined Jul 18, 2013
23,658
I don't think NFPA book refers to using ESR relay to electromechanically disconnect all devices in circuit. Am I missing something here?
The reason is that AFAIK Safety Relays are not mandatory in N.A. it may well be in the near future.
But they have been in common usage in the EU. for some time and are found in the regulations there.
It may be wise to include them in future designs.
Max.
 

Thread Starter

maitrey

Joined Sep 4, 2014
72
If working in N.A. environment then use NFPA79 and NFPA70 (NEC).
If required to there is documents out there to become familiar with European, IEC codes etc.
Also pay attention to earth grounding requirements.
Max.
Very informative, I work in pharmaceutical companies which requires cGMP standards, CFR 21, UL 508A and NRTL requierments.
 

Thread Starter

maitrey

Joined Sep 4, 2014
72
If working in N.A. environment then use NFPA79 and NFPA70 (NEC).
If required to there is documents out there to become familiar with European, IEC codes etc.
Also pay attention to earth grounding requirements.
Max.
I never had such documents to refer to. Our company only builds panels for US market.
 

MaxHeadRoom

Joined Jul 18, 2013
23,658
I am not that familiar with those regulation requirements as most of my work was in Industrial machinery.
PS: every machine I saw that was imported from Europe had a Safety relay incorporated in the panel.
Max.
 

SamR

Joined Mar 19, 2019
3,498
For residential, commercial, and industrial construction the NEC rules. For developing a product for commercial sale, not only will the NEC need to be adhered to but it will also need UL testing and approval. There are many gray areas where standards are not applied and there are areas where other additional standards come into play. There are also companies, such as electrical utility providers, that do not use the NEC at all and have their own standards. Your employer should guide you in this and may even have other in-house corporate standards that also need to be adhered to. And as one elder Senior Project Engineer used to tell me "standards are good guides as to better practice, but sometimes they just don't apply and even when they do apply they aren't written in stone." It is a huge gray area...
 

MaxHeadRoom

Joined Jul 18, 2013
23,658
Equipment built for resale purposes generally requires the necessary control body inspection and sticker UL/ULC . etc.
Max.
 
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Thread Starter

maitrey

Joined Sep 4, 2014
72
For residential, commercial, and industrial construction the NEC rules. For developing a product for commercial sale, not only will the NEC need to be adhered to but it will also need UL testing and approval. There are many gray areas where standards are not applied and there are areas where other additional standards come into play. There are also companies, such as electrical utility providers, that do not use the NEC at all and have their own standards. Your employer should guide you in this and may even have other in-house corporate standards that also need to be adhered to. And as one elder Senior Project Engineer used to tell me "standards are good guides as to better practice, but sometimes they just don't apply and even when they do apply they aren't written in stone." It is a huge gray area...
Yes, I think that's exactly what I witnessed so far that we don't comply to all standards in one single panel and it varies depending upon the design criteria. It changes so many times that I am scratching my head everytime I come across new one.
 

SamR

Joined Mar 19, 2019
3,498
Also, remember that "Standards" vary with what is required locally. It can be city, county, or even state regulations that set forth the standards required to be met within their legal jurisdiction. The National Fire Protection Association which produces the National Electrical Code as one of their "standards" is not a regulatory agency and is merely the provider of one of many accepted "standards" that may, or may not, be adopted by a regulatory agency with legal penalties for non-conformance to that adopted standard within their jurisdiction.
 

Thread Starter

maitrey

Joined Sep 4, 2014
72
Is there a NFPA 70 PDF available anywhere to download? I just found out that there are two types of NFPA books,

1. Only codes and standards
2. Codes and standards with reference diagrams

The new 2020 edition is not available in PDF format yet but 2017 is. Just wondering if there is a link to download it for free.
 

Papabravo

Joined Feb 24, 2006
16,840
Is there a NFPA 70 PDF available anywhere to download? I just found out that there are two types of NFPA books,

1. Only codes and standards
2. Codes and standards with reference diagrams

The new 2020 edition is not available in PDF format yet but 2017 is. Just wondering if there is a link to download it for free.
Sometimes there is, but not always. In my experience standards documents carry a fairly hefty price tag to support the organization that promulgates them. They are copyrighted so anybody who provided a free PDF, without their permission, would be breaking the law. As the standard ages these prices and restrictions tend to relax. For example the USB 2.0 spec is a free download and has been for over a decade. Sometimes you have to become a member of the organization with a hefty membership fee. Most engineers who need this stuff have the company pay for it, but that is not always an option.
 

SamR

Joined Mar 19, 2019
3,498
NFPA publishes 2 NEC handbooks. A barebones paperback and a more expensive illustrated with expanded explanations and comments hardbound book. There is not a great deal of change from year to year and we bought updated handbooks every ~10years. I don't think their standard wire tables have changed in forever.
 

Thread Starter

maitrey

Joined Sep 4, 2014
72
Yeah, I don't think so either. I refer to NFPA 79 book which is 2007 version and it's still relevant to current standards. Nothing much have changed in latest versions.
 

Thread Starter

maitrey

Joined Sep 4, 2014
72
Equipment built for resale purposes generally requires the necessary control body inspection and sticker UL/ULC . etc.
Max.
I don't know if you recall but you shared a 2007 NFPA 79 copy on my previous thread and the article I was looking for is there only. I wonder why I couldn't find this earlier. You really have to know where to find correct article # and details for what you looking for. In my case, I was looking for a reference to use Safety guard relay with Emergency stop to electromechanically disconnect all my loads. There it is i finally found it!! Thank you :)

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