How To Operate Your Roof or Gutter Heat Tape?
Several individuals recently sought out VT Ice Dam Solutions for advice on how to operate their heat cables. What temperatures should they turn their roof heat cables on at? Should they let the ice dam start forming first? How long did they need to leave the heat tape on for?
There is a lot of misconceptions out there being offered as expert opinions. First of all, let's deal with the two types of heat cables that are used for ice dam prevention first. Constant wattage heat tape is the thin round heat cables most often purchased at hardware or big box stores. They are inexpensive and a favorite choice among the DIY crowd. Here is a video posted on Amazon with a guy who chips out the ice dam that has formed on the roof edge. Just scroll down to the reviews and the video is posted there. This guy stands on top of a step ladder in the middle of winter and chisels away at the narrow channels around the heat cable to open it up. Its amazing - this is so dangerous. I thought the purpose of the heat tape was so that you didn't have to get up there and chop at the ice! The other type of heat cable is the self regulating style. Although, these cables are more often used in commercial and industrial settings, there are self regulating cables that are used in the residential market too. Be careful when making a self regulating heat cable purchase. There are inferior brands with a short life span and limited heat output. Contact us if you want to purchase the same heat cables we use for our roof and gutter ice melt systems.
The misconception is that these cables get turned on after ice is visible. This is not true. The cables should be turned on when snow is expected - perhaps an hour or two before snow starts falling. This is true for both the zig zag style of installation or when radiant roof panels are used. The roof heat cables should be warm to start melting immediately when snow is falling. We have heard from fellow ice dam prevention contractors who use thermostat controllers with moisture sensing that these controllers turn on too late. It takes time for heat cables and radiant panels to heat up. If they are not warm when the snow starts falling they can be overwhelmed and may not catch up.
Another misconception is that heat cables should only be when temps are above freezing. This probably results from experience with hardware store heat tape. The limited power output means they are less effective as the temperature drops. It is true that as the temps near zero degrees self regulating heat cables also struggle. But, that is far colder than when most snow falls (except, perhaps at higher elevations). Heat cables and radiant panel roof ice melt systems should generally be energized between 10 and 34 degrees. These are the temps at which ice dams form and the heat cables will work best (of course "best" is a relative term in connection with hardware store heat cables).
Heat cables and the radiant ice melt systems should be left on while there is significant snow on the roof. This is something that varies. Some roofs have less heat loss melting the snow. Some have solar gain (where the sun melts the snow). Because of this, some customers can turn their systems off earlier than others. For the first year, observe how your roof works and you may be able to economize by shutting your system down even when some snow is present on the roof. Others rely on thermostat controllers. Learn from our experience. Stay away from the cheap controllers sold with the thin round constant wattage heat cables. These fail way to often to be reliable. Also, avoid the little plug in temp cubes. Again, not reliable. We have already commented on others experience with the moisture sensing thermostat controllers. For us, we have settled on a digital controller - the AS Digital Ambient Sensing Thermostat Controller from Bylin Engineered Systems. We have seen another company copy this controller - they believe it is a great setup too. These digital controllers keep the heat cables on at a preset range, turning the cables off outside of that ice dam forming temperature range. Great choice.
So to review:
- Use commercial grade self regulating heat cables
- Turn the heat cables on before it starts snowing
- Keep the roof and gutter heat tape on while there is snow on the roof depeding on local conditions
If you want more information or would like to purchase an heat cable system, please contact us.