This piece was originally published in the May 2018 issue of electroindustry.
Peter Lafreniere, Product Manager–Cable, AFC Cable Systems, Inc.
Mr. Lafreniere leads product strategy for the Cable Solutions business unit’s product line and is responsible for its strategic innovation initiative.
As heat waves, cold spells, hurricanes, and floods attack all regions of the country, contractors and engineers need to consider resiliency as they build critical infrastructure to withstand these natural disasters.
To ensure electrical safety during extreme weather situations, industry workers and electricians must understand the environment they are building in to better utilize appropriate cables and conduits for safe and secure construction.
Let’s take a look at the best practices for selecting cables for potentially dangerous jobsite conditions, including wet environments and extreme temperatures.
MC jacketed cable
According to the National Electrical Code® (NEC), wet locations are installations underground or in concrete slabs or masonry in direct contact with the earth, in locations subject to saturation with water or other liquids, and in unprotected locations exposed to the weather’s elements.
Locations considered “damp” and protected from the weather are still subject to moderate degrees of moisture and require appropriate cables and conduits to protect electrical products and the overall structure of the build.
MC cable with a PVC jacket
In most instances, the conductor insulation determines the appropriate application for dry, damp, or wet environments. Engineers must recognize that while some wires are transferable from damp to dry locations, there are properties of dry location wires that do not possess the appropriate insulation suitable in wet locations.
True or False? Cables and conduits need to be replaced when exposed to floodwaters.
TRUE. Always immediately replace armored and metal-clad cables when exposed to extensive moisture and water resulting from hurricanes or extreme rain. Floodwaters contain numerous contaminants and sewage that can be hazardous to electrical products, potentially causing the insulation to fail or become conductive.
Use corrosion-resistant jackets and wet location–rated conductors in areas that are predisposed to wet elements. A common cable type that is rated for wet locations and complies with the NEC is a metal-clad (MC) cable with a polyvinyl chloride (PVC) or polyethylene jacket, due to its durability, moisture and oil resistance, flame-retardant features, and superior resistance to weathering and soil environments.
With heat waves and cold spells affecting all climates and regions, it is crucial to understand the proper cabling solutions that can withstand the extreme fluctuation of temperatures. When exposed to high temperatures, cable materials can experience weakened electrical properties and loss of tension as a precursor to devastating failure. Cables exposed to cold temperatures can become brittle and can even shatter when bent or flexed.
Hi-low temperature type LFMC. All illustrations courtesy of AFC Cable Systems, Inc.
To determine safe working limits, all conduits must undergo testing. Underwriters Laboratories (UL) conducts low-temperature flexibility, cold bend, cold impact, and sunlight resistance as well as other physical property testing to determine the appropriate operating temperature range for the conduit.
True or False? Conduits can exceed listed UL® temperature ratings.
FALSE. Operating at or close to maximum or minimum temperature ratings for extended periods of time can shorten service life. Always confirm that conduits can comfortably handle the high and low temperature requirements of an installation in your environment. Common temperature ratings for high-low temperature conduits are a low of -55°C / -67°F to a high of 105°C / 221°F when used in a dry location. For wet or oily conditions, ratings range from a low of 60°C / 140°F and 70°C / 158°F, respectively.
Before installation, learn what cable materials are best suited for extreme temperature fluctuations to maintain mechanical and electrical properties. PVC and silicone are proper jacket materials for these environmental conditions; both provide flexibility, flame-retardant properties, chemical and moisture resistance, and wear resistance. To determine what cable solution is best for your environment, it is always important to work closely with a field technician in your area.
As contractors, electricians, and architects build and renovate structures in 2018, they should incorporate resilient products and materials into their design elements as a precaution against the hazardous effects of extreme weather events. As these natural disasters persist, the construction industry may forgo general practices and instead adapt and adopt environment-specific products to prevent unnecessary damage and to uphold safe working conditions within facilities.