Electric cable heating of roof drains

[TSN79]

I work for a contractor and we're currently discussing drains on the roof of a building, and whether they should have electric cable heating around them. It gets cold here and snow does accumulate on the roof. Under what circumstances should cables be used and not? Pros / cons?

 

[FredGarvin]

To my knowledge, the use of heat tape or heater cords is used when the outside temp fluctuates between freeze and thaw within the day or if you have sufficient heat loss through the roof to present melting below freezing temperatures.

I have heat wires run in my second story gutter because of icicle formation during the winter. They have been the best option so far. At my place of business, we use heat tape on a lot of roof drains because the heat loss through these old buildings is pretty bad. They definitely help keep them clear, although sometime the maintainence guys have to go up on the roof and clear them out.