To Whom it may concern:
Safety tips for water-immersed Type NM-B nonmetallic-sheathed cable, i.e.,
Romex®
Type NM-B nonmetallic-sheathed cable (commonly called "Romex®" in the industry) is
Listed by UL for use in normally dry locations in accordance with the National Electrical
Code® (NEC®) under the product category "Nonmetallic-sheathed Cable (PWVX)."
General Guide Information for this category can be found in UL's Online Certifications
Directory.
Decades ago, the outer jacket of this cable changed from an impregnated, braided
covering to polyvinyl chloride (PVC). In the mid-1980s, the internal conductor insulation
went from a temperature rating of 60°C to a 90°C rating, and the required marking was
changed from "Type NM" to "Type NM-B."
The older, braided jacketed version of this cable has less resistance to water ingress than
the newer, PVC-jacketed version, and if subject to immersion, such as from flooding, the
suitability for continued use is unknown. Any cable of this type that has been subjected to
flooding should be replaced without question.
In general, cables with PVC insulation and jacket can withstand immersion in clean water
for a short period of time without being damaged as long as the ends are not immersed. If
the ends of the cable are immersed for any period of time, however, the internal paper
wrapping around the bare equipment-grounding conductor will absorb and transfer the
water into the cable assembly. The water may then start degrading the insulation or
possibly corrode the conductors. If the cable comes into contact with contaminated water,
the contaminants may also act on the insulation or conductors. Over time, failures can
occur.
In a flooding situation, there is no way of knowing how long the cables were immersed in
water, or what types of potentially corrosive substances may have been in the water that
flooded the cables. As was widely reported after Hurricane Katrina, raw sewage and
chemicals were known to be in the floodwaters afflicting the Gulf Coast region of the
United States. Nonmetallic-sheathed cable has not been investigated by UL for this type
of exposure. Therefore, it is not possible for UL to state that cable in a particular
installation is acceptable for continued use after having been subjected to the flooding.
The safest approach is to replace any nonmetallic-sheathed cable that was immersed in
water for any period of time during the flooding.
The devastation of a flood is enormous. As the contaminated waters recede, there may be
even more threats to your personal health and safety. By taking basic precautions, you can
help prevent many injuries. IAEI and UL urge you to always put the safety of your family
first.
For more information, contact your local electrical inspector or visit www.iaei.org
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