COLD NIGHTS ARE HERE — WATCH INSTALLATION TEMPERATURES
Large reels of cable change temperature slowly. Low nighttime temperatures can cause installation problems the following day.
- Published in Southwire's Power Cable Update newsletter in January 1998
- Reprint permission granted
When the nights are cold and the days are warm, be careful with your cable. Cable made of thermoplastic material such as PVC may stiffen in the cold.
A Fine Print Note (FPN) in NEC Section 310-13 says, "Thermoplastic insulation may stiffen at temperatures colder than -10°C (+14°F)." This means you should exercise care during installation when the cable has been recently exposed to low temperatures.
Senior Applications Engineer Sid Ticker says, "This is not a formal requirement, but it Some cable jacket and insulation materials should be heeded. Installing cable when the insulation is too cold can damage the cable."
Sunny Days May Not Be Enough
"When days are sunny and nights are cold, we start to hear from people having installation problems with cable insulation and jackets," Ticker says. He adds, "If a reel of cable has been sitting outside on a night when the temperature drops below critical levels, the inside of the reel can still be cold long after the air has warmed up on a sunny morning. If your installation crew starts to pull cable off the reel, they may damage the insulation or the jacket."
What can you do? "Keep the cable warm," says Ticker. "Move it into a heated area for some time before you install it. Remember that reels of cable change temperature slowly. It takes a while for heat to penetrate layers of cable. Keep it there long enough to make sure it's warm all the way through." Southwire recommends leaving cable reels in heated storage for at least 24 hours before installation.
PVC compounds stiffer sooner
Some cable jacket and insulation materials handle cold better than others. Thermoplastic materials such as PVC jackets and insulation are most apt to stiffen in extreme cold.
Southwire concurs with the NEC Fine Print Note, and advises installers to take caution with thermoplastic materials at temperatures below -10°C (+14°F). |
