The Do’s and Don’ts of Selecting the Right Cabling Solution
By Peter Lafreniere
After last year’s bout of hurricanes, flooding, wildfires, heat waves and cold spells across the country, product resiliency is key for contractors and engineers in 2018 as they rebuild and renovate destructed areas to withstand these natural disasters. To keep facilities up and running through extreme weather situations, it is vital for industry workers to understand the environment they are building in, and to better use appropriate cables and conduits for safe construction. Whether renovating or rebuilding from ground up, the proper installation of cables and selecting conduits with appropriate insulation and jacketing should be the primary focus during redevelopment. While some damage is non-preventable, a large portion of issues and safety hazards can be avoided through proper cabling solutions suited for different environments. Let’s take a look at the do’s and don’ts of potentially dangerous jobsite conditions including wet environments, fire hazard areas and extreme temperatures.
UL Low Smoke Zero Halogen Type LFMC
The definition of a wet location according to the National Electric Code (NEC) is: 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 weather’s elements. Even 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.
In most cases, the type of conduit insulation determines the application for dry, damp or wet environments. It is important to note that while most wires approved for damp and wet locations can be used in dry environments, there are properties of dry location wires that do not possess the appropriate insulation suitable in wet locations.
UL Liquidtight Type LFMC
DON’T let armored and metal clad cables lie in stagnant floodwaters after a hurricane or rain season. Floodwaters contain sewage and numerous contaminants, which can be hazardous to electrical products. These contaminates may have a detrimental effect on the insulation system that surrounds the electrical conductor, causing the insulation to fail, or worse, become conductive. Always immediately replace armored and metal clad cables when exposed to extensive moisture and water resulting from hurricanes or extreme rain.
DO use a corrosion-resistant jacket and wet location-rated conductors in areas that are predisposed to these elements. A common jacket style cable that complies with the NEC and is rated for wet locations is a metal clad cable with a PVC or PE jacket, due to their durability, moisture and oil resistance, flame-retardant features, as well as superior resistance to weathering and soil environments.
Environments Subject to Wildfires
As contractors begin to rebuild properties after the mass destruction of wildfires in Western states, there are simple cabling decisions and product swaps that will improve the safety of individuals and equipment in the event of another wildfire or heat-related natural disaster.
DON’T use cables composed of halogen. Halogens are commonly found in the polymers used for conduit and cable jackets due to their flame-retardant properties and cost effectiveness. While flame-resistant, these polymers containing halogens such as polyvinyl chloride (PVC) and ethylene propylene (FEP) emit toxic gases and smoke when burned. These toxic, corrosive gases cause damage to equipment and pose a safety concern to individuals in the building during a fire.
PVC Jacketed MC Cable
DO use Low Smoke Zero Halogen (LSZH) Liquid-Tight Flexible Metal Conduits (LFMC) in areas predisposed to fire hazards and industrial applications that can become overheated due to high temperatures and poor ventilation, including rail, aircraft, construction and offshore installations. LSZH Liquid-Tight LFMC use a halogen-free thermoplastic polyurethane jacket, providing the same flame-retardant features while limiting smoke and corrosive gas emissions that can harm individuals and damage equipment. When in contact with flames, LSZH-LFMC products release smoke at a lower rate and density, creating a safer environment and more distinct exit path for workers and individuals during a fire.
When selecting LFMC products, select conduits with hot-dipped zinc galvanized low-carbon steel core, thermoplastic polyurethane jacket, and ensure it complies with the following standards:
• ASTM E 162 Flame Spread Index
• ASTM E 662 Smoke Density Generation
• Bombardier SMP-800C Toxic Gas Generation
• UL 94 Tests for Flammability of Plastic Materials for Parts
Extremely Hot and Cold Temperatures
With heat waves and cold spells affecting all regions of the country, 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 loss of tension and weakened electrical properties as a precursor to devastating failure. When exposed to cold temperatures, cables can become brittle, and can crack or shatter when bent or flexed.
All conduits must undergo testing to determine safe working limits. Underwriter’s Laboratories (UL) conducts low temperature flexibility, cold bend, cold impact and sunlight resistance, and other physical property testing to determine the appropriate operating temperature range for the conduit.
DON’T exceed conduit temperature ratings, and select conduits that can comfortably handle the high and low temperature requirements of an installation. Operating at or close to maximum or minimum temperature ratings for extended periods of time can shorten service life. Common temperature ratings for hi-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.
DO research what cable materials are best suited for your environment or application to maintain mechanical and electrical properties during extreme temperature fluctuations. Proper jacket materials for these environmental conditions include PVC and silicone—both providing flexibility, flame-retardant properties, chemical and moisture resistance, as well as 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.
MC Luminary Jacketed Cable
Rather than having to rebuild after devastation, contractors, electricians and architects should incorporate resilient products and materials into their design elements as preventative measure against extreme weather events and their hazardous effects. In the coming years, the construction industry may forgo general practices and, instead, adapt and adopt environment-specific products to get in front of these natural disasters to prevent unnecessary damage and to uphold safe working conditions within facilities. UP
About the author: Peter Lafreniere is Product Manager-Cable for AFC Cable Systems.