from Guest Blogger: Nick Birk, Product Line Manager, Belden
As industry readers well know, the National Fire Protection Association (NFPA) is an authority for any organization operating or manufacturing electrical equipment. The NFPA currently maintains some 300 standards, which often form defacto regulations in their product categories.
One of these—NFPA 79, The Electrical Standard for Industrial Machinery—was recently updated from its prior 2012 publication. The 2018 version holds a new key clause for our VFD users. This VFD Cabling section is worthwhile to call attention to because the potential impact for users can be profound, especially when it comes to the type of cable that is allowed to be specified.
As with many regulations, NFPA 79 2018 is lengthy, but the area of most vital importance to VFD users can be found in Section 188.8.131.52:
“Electrical conductors and equipment supplied by power conversion equipment as part of adjustable speed drive systems and servo drive systems shall be listed flexible motor supply cable marked RHH, RHW, RHW-2, XHH, XHHW or XHHW-2.”
What does this really mean? Moving forward, you would need to look and confirm that any of these six designations (RHH, RHW, RHW-2, XHH, XHHW or XHHW-2) are printed on the cable jacket and act accordingly if not to avoid fines and ensure safety. If you are running a plant this is important for anyone specifying cable, pulling your wiring, or doing your installs to know. If you are a subcontractor, this is critical for you as well because nobody wants to be stuck tearing out and repurchasing wiring because it doesn’t meet code.
Relative to the code it is also important to “read between the lines”. If those are what is allowed, what is “no longer allowed or outlawed”?
That is the most significant because THHN is often used as a lower cost alternative to truly designed VFD cables. In addition, you may want to consider specifying or purchasing a high quality VFD cable that is specifically noted as meeting 2018 standards because there are a few more “read between the lines” as a result of the new regulations:
Although operators accustomed to working with quality VFD cable suppliers should have little cause for concern, there is, especially in the short term, an increased danger of being the victim of “misleading” cable claims. Some manufacturers of “outlawed” thermoplastic and similar cables may strive to unload their excess inventory—still deemed acceptable for many non-machine applications, but now significantly curtailed in their allowable scope of usability for our typical applications.
One thing to look out for are claims using abbreviated phrases such as “NFPA 79 Compliant” or “Meets NFPA 79 Standards”. Specifiers, engineers, or installers should instead now be on the lookout for the phrase “Meets NFPA 79 2018 Standards” to ensure that the cable doesn’t simply meet the prior NFPA 79 2012 standards and you don’t get into hot water with an astute electrical inspector.
We believe that the new standard is of vital importance in optimizing safety for all VFD machinery applications. Specifically, we believe the biggest thing to watch out for is ensuring the use of THHN comes to an end.
If you have questions, the Rumsey or Belden team is glad to be a technical resource. We want to help you ensure that you are protecting your people, your equipment, and you in the safe zone for long-term electrical safety compliance.
Known as the originator of the product category, and a Rockwell Automation Encompass Partner, Belden has been supplying VFD cables for more than 20 years. Always intent on providing nothing but the highest quality cables, Belden has not had to make any changes to be fully compliant with the stringent new NFPA 79 2018 specs. Belden also stands behind that promise with a full 10-year factory warranty—otherwise unheard of in the industry.
Author Note: This post is an adaption from a blog originally published on Belden’s Industrial blog.