With UL requirements and NFPA
standards each holding sway over
different aspects of electrical compliance, it’s always been tough to figure
out whether your cable choices will pass
regulatory muster.
The job of picking compliant cables
recently became even tougher. A new
version of NFPA 79, the main standard governing the electrical safety of
industrial machines, drastically changes
the compliance picture. To read more about the changes and how they’ll
affect your cable selection practices,
download our new technical paper on NFPA 79 compliance. And check out
the following answers to your most commonly asked compliance questions:
is NFPA a law?
No. NFPA–79 is the key electrical safety
standard accepted by machine builders, installers and buyers in the United
States.
Does a machine have to comply with NFPA79?
In most cases, yes. The need for NFPA compliance
ultimately depends on the application details and whether the machine is being
installed in a building. When in doubt, it’s a good idea to comply with NFPA 79
to maximize safety and avoid the potential for
litigation.
Will machine builders and buyers
standardize on the new edition of NFPA79?
Yes. Concerns about safety and
liability issues will force compliance with the new 2012 edition of the NFPA
standard. Buyers of industrial equipment are unlikely to purchase non-compliant
machines that could increase the potential for litigation.
Who decides which cables can be
installed in the field?
Engineers may assume that UL
dictates cable choice, but the real authority falls with electrical inspectors who
determine compliance with the National Electrical Code. UL, however, does
control the electrical, physical and environmental testing requirements and
approvals that, in practice, determine cable usage in the field
are UL listed cables always allowable
for use on a machine?
Not necessarily. There are machines
that use UL listed cordage incorrectly. For example, some listed cables are
only intended for temporary applications. Other listed cables may not meet the
minimum stranding requirements needed for NFPA 79 compliance.
What’s special about MTW approval?
Machine Tool Wire (MTW) approval
requires that the cable be flexible and offer a high degree of mechanical
durability. These characteristics allow it to perform under the challenging conditions
surrounding industrial machines.
Are all MTW cables oil resistant?
Yes, all compliant MTW cables minimally meet the requirements of
the UL Oil Res I test. For applications requiring a more severe exposure, the
more rigorous Oil Res II test is also a permitted option.
Can I run MTW cable into building
infrastructure?
No, not unless it is dual marked
with the appropriate UL Listing. Cables marked “TC” offer the high flammability
rating needed for installation in
building infrastructure. The MTW requirements alone mandate that a cable only
meet a minimal flame test known as VW–1.
Can cables be left exposed when
going from the machine to the cable tray?
In most cases, no. Cables designed
for exposed runs must have a “TC-ER” approval
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