Roof and gutter deicing technology helps protect homes and facilities from the ravages of winter weather. Safety is the priority when bringing electrical solutions that result in converting ice to water. Installation and operating instructions for controllers and heaters reinforce this priority. Installing a safe system usually occurs during the construction and repair season, already underway during this National Electrical Safety Month.
It’s important to remember that improper installations – those that ignore manufacturer instructions, best-practice installation methods or are not NEC, CEC or other agency compliant – can result in catastrophes.
Consider wet fire. A wet fire occurs when an arc or arc track develops between the current carrying conductors or between a current carrying conductor and ground. Environmental Technology Inc.’s experience suggests that any type of heater construction could be susceptible to a wet fire – even mineral insulated heaters.
ETI staff have observed two wet fires in the process of igniting: a residence and a church. Each one was the result of improper, noncompliant installations; interrupted before causing property damage; and completely avoidable. Either could have caused a catastrophic fire.
The Good News
Fortunately, modern heater construction and NEC requirements have essentially eliminated the wet fire problem in properly installed deicing systems. Heaters are now constructed using self-extinguishing polymetric or refractory insulating materials. That is, the insulation will not continue to burn in the absence of a flame or high-energy source.
The NEC and all heater safety standards require that the heater be shielded with a braid or enclosed within a metallic tube. Both the shield and the metal tube must be grounded. This fundamental safety scheme ensures that the current resulting from an insulation failure flows to the ground.
“GF—” What kind of protection was that again?
The final component in this installation safety equation is either a ground fault circuit interrupter – GFCI – or ground fault equipment protection circuitry, GFEP. Upon sensing a ground current exceeding a threshold value, 6 MA in the case of a GFCI and 30/60/120 MA when using a GFEP, voltage to the heating cable is interrupted, removing the energy necessary for continued combustion. ETI’s GF Pro interfaces with up to two standard Environmental Technology sensors to meet site requirements. The CIT–1 sensor may be roof or mast mounted and can be paired with the GIT–1 sensor for gutter applications.
Safety requires using a shielded heater in combination with a GFCI or GFEP device. The shield must be grounded or it will not perform its safety function.
One of the potential wet fires observed by ETI personnel wet fire was due to an installation error: the heater shield was not grounded. The heater insulation was damaged which allowed water to enter. The water breached the insulation thus forming a conductive path. The problem was discovered before the fire began. Steam from the heated water was discovered by the homeowner who had the common sense to pull the circuit breaker on the problem heater. This heater was protected by a GFEP, the ground current had not reached the 30 MA trip point.
The church’s situation occurred in a segment of cable used to keep a drainage path open through the downspout. It seemed that the end of the cable routed through the downspout had deteriorated due to extensive submersion or a chemical attack of some kind. The wet fire had started on the cable. As in the previous case, someone at the church spotted smoke and pulled the circuit breaker supplying voltage to the defective heater.
Examination revealed that none of the 30-ish circuit breakers controlling the system had been equipped with the GFEP protection as required by the NEC.
Draw Your Conclusions
The conclusion drawn from these two incidents is that each was preventable. Homeowners may allow economic considerations to enhance one choice over another. Perhaps the lack of appropriate training is a culprit. Following ETI and heating cable installation instructions and understanding local and national electrical codes for compliance should result in deicing protection that leads to continued personal and property safety.
Be sure to contact Environmental Technology Inc. if you have any questions in understanding the proper and safe installation of our products.