HEAT CABLES

Heat cables can be used to prevent leakage due to ice damming. They can also be used to control water run off in the winter season. Heat cables will melt a channel through ice and keep that channel open so the water is allowed to run off the roof and along the cable. Heat cables are not intended to melt all the ice and snow away. It is critical that heat cables be installed properly; otherwise, they may just melt more water to leak into the roof.

What kinds of heat cables are available?

There are two different types of heat cables that are available today.

The first type has a plastic jacketed heating element that has a short extension cord attached to it with an electrical plug. This cable is available in a number of different lengths and should be plugged directly into an electrical outlet with ground fault protection. Typical lengths of these cables are 20 to over 200 feet. Note: This type of cable should not overlap itself or touch adjoining heat cables to prevent the cables from burning out prematurely. In addition, this style heat cable cannot be cut or altered in any way. Once these cables are cut or broken in two, they cannot be repaired.

The second type of heat cable is a “self-regulating” heat cable. This cable comes on a spool and is unrolled to the desired length, cut and an end seal is attached. This type of cable will regulate how warm it gets by reducing the amount of electricity it draws, as it gets hot. This “self-regulating” feature makes this type of cable more economical to operate and prevents it from overheating and burning out. Self-regulating cables may also touch together and overlap other heat cables. These features all combine to allow this type of cable to be left on longer. “Self - regulating “ heat cables require that they be “hard wired” into the electrical system of the house using a special connector kit.

How should heat cables be installed?

The most critical aspect to understand about heat cable installation is that the cables must be installed in such a manner that they will direct the water along the cable all the way off the roof. The cables should be installed so the melted water cannot freeze at a point just past the end of the cable and block off the drainage openings.

Heat cables are normally installed zigzagged along the lower edge of the roof extending up the roof to a point approximately 24 inches inside the wall line. The low points of the heat cable loops must extend either off the roof or down into the gutter near a heat cable that lies in the gutter and extends down the downspout and out the bottom 1-2 feet.

Heat cables are installed with clips that fasten either to the shingle tab or to the roof deck under a shingle tab. Clips should also be used to hold two cables slightly apart when the water runoff will be transferred from one cable to another.

An electrician should be consulted to make sure the electrical circuits are able to handle the heat cables. The heat cables should have a control switch with a pilot light that can turn them on and off. The “self-regulating” heat cables need to be hooked up directly to the electrical system by an electrician.

If heat cables are installed on smooth, hard roof surface materials such as tile, slate and metal, ice and snow guards must also be installed with the cables. This is to prevent the ice and snow slide that commonly occurs on these types of roof surfaces. This ice and snow slide will tear the heat cables off the roof if it is allowed to occur.

When should I turn the heat cables on?

The answer is any time that there is water trapped behind an ice dam. Actually this can be different for each home. It would depend on the amount of heat loss, the amount of snow and the outside temperature. If the outside temperature is above freezing and the channels are open for the water to run off, the cables do not need to be in the on position until it starts to freeze again.

Most people do not monitor their heat cables this closely and consequently leave them on for long periods of time. This is a better solution than forgetting to turn them on altogether and damaging interior surfaces by water leakage, however it can cause the heat cables to burn out more quickly than they normally would.

Are there areas that heat cables should not be installed?

The plug in type heat cables should not be installed on flat roof areas. If a flat roof should require the installation of heat cables, only the “self-regulating” heat cable should be used. Heat cables should not be installed on combustible materials.

It is important that gutters and downspouts are cleaned out to allow the heat cables to function properly.

The “self-regulating” heat cable is superior to the plug in type of heat cable in many ways. The cost is also significantly more for the “self-regulating” type of heat cable.