A Safety Alert on Heat Tapes
By Mike McClintock
They are used mainly to keep water pipes from freezing, but they also prevent ice dams at gutters, downspouts and roof edges. Heat tapes are useful as well in many other situations, including exposed fuel-supply lines on mobile homes and refrigeration piping on commercial fishing boats.
A modern heat tape certified to meet recognized standards by Underwriters Laboratories (UL) or the Canadian Standards Association (CSA) can be used safely to prevent freeze-ups and costly repairs.
But according to the Consumer Product Safety Commission (CPSC), heat tapes are the cause of approximately 2,000 fires, 10 deaths and 100 injuries every year. Some figures for deaths and injuries are higher and include estimates of property damage exceeding $25 million a year.
The heat tape that most homeowners use comes in stock lengths, like extension cords, that run from a few feet long to almost 100 feet. You plug one end of the tape into an outlet and spiral-wrap the rest around a pipe.
Modern tapes have a built-in thermostat that automatically calls for power (and the resulting heat) as the surrounding temperature drops near freezing and cuts power off as the temperature rises. Those tapes do not draw electricity all the time, even though they remain plugged in.
A cycle of repetitive heating and cooling is one of several factors that can lead to fires. Another is exposure. Many people leave heat tapes in locations where they get hot in summer, cold in winter and wet year-round. As a result, the wire insulation can develop cracks and let in moisture that causes a short circuit.
Fires also can be triggered by improper installation. For example, when some tapes are wrapped tightly together or lapped over themselves, they can generate enough heat to melt their insulation and expose the wires inside. When the wires make contact, sparks can ignite nearby building materials.
No one can be sure exactly how many fires start with heat tapes because the products often are completely consumed in a blaze. But reports by fire investigators across the United States and Canada regularly place the blame on older and improperly installed heat tapes.
Even the U.S. Coast Guard has issued a warning about heat tapes used on boats.
One of the most significant cases involved animals instead of people. A fire at the Philadelphia Zoo in December 1995 killed 23 animals, including a family group of six lowland gorillas, three orangutans, gibbons, lemurs and other primates, all of which were endangered species.
Fire and zoo officials said the fire was caused by improperly installed wires that heated ceiling pipes. Soon after the fire, the CPSC reissued its recommendations for the safe use of electric heat tapes.
The following guidelines incorporate those CPSC suggestions as well as those of manufacturers and fire inspectors. They encourage a cautious use of the product that may include more limitations than some manufacturers' instructions indicate.
Installation and maintenance
* Purchase UL- or CSA-certified heat tape. Be sure that the tape has a grounding, or three-prong plug.
* Heat tapes should be installed in compliance with national, state and local electrical codes, and in accordance with manufacturers' instructions. Because heat tapes differ, some products may be suitable for one kind of installation but not another.
* Do not use heat tapes that are designed specifically for water pipes on gutters, driveways or fuel lines.
* As an extra margin of safety in all cases, plug the heat tape into a grounded outlet that is protected by a quick-tripping circuit breaker called a ground-fault circuit-interrupter (GFCI). Install heat tapes on exterior surfaces and exposed pipes, not inside walls, floors or ceilings. Apply them directly on the pipe you want to protect from freezing, not around pipe insulation.
* To avoid overheating, don't cover heat tapes with insulation, even though some manufacturers may permit it. If you do add insulation according to manufacturers' instructions, use a nonflammable type, such as fiberglass, not foam or vinyl insulation that could catch fire from a failing heat tape.
* Do not wrap heat tape over itself, even though some manufacturers may permit it. Do not use metal bindings of any kind to secure heat tape to piping or roofing.
* If the heat tape has a thermostat, check the instructions to see if the thermostat should rest against the pipe and be covered with insulation to sense pipe temperature, or be left hanging and uncovered to sense air temperature.
* Check heat tapes and their electrical connections at the beginning of the heating season and monthly during operation. Remove a heat tape if you see cuts or cracks, charring, animal chew marks, bare wires, a loose or missing end cap, or any other signs of deterioration.
* Replace any tape that has been exposed to the elements for more than three years. Replace any uncertified tape, even if it shows no signs of wear.
© Copyright 2000 The Washington Post Company