As mentioned above you will use about 8w per linear foot of ice melting cable.
How long roof ice melt.
Cut the leg part off the stockings and fill them up with 2 3 pounds of ice melt and tie the ends.
Clip in the cable along the same zigzag pattern as the shingle clips.
They form when snow melts in warmer areas of the roof sending water running down toward the edge.
Ice dams can pose many problems.
You say that for 20 we can get 60 tablets.
Formulated to last up to 24 hours melt calcium chloride crystals go to work immediately upon contact with snow and ice and continue working all day long to ensure your surfaces are safer and ice free.
If you still have snow or ice on your metal roof there are several different tools you can use to melt the snow like heat cables calcium chloride or hot water.
A typical 120 foot long roof edge with 6 12 overhangs and no gutters deicing will need about 291 feet of cable.
In this video master electrician for ask this old house scott caron helps a homeowner install heat cables on his roof to stop ice dams.
As more and more water melts down the roof and refreezes at these locations ice builds up and forms a blockage or dam.
How many tablets are needed to melt the snow and ice off the roof and off the gutters.
The water trickles down between the layer of snow and the shingles until it reaches the eave of the roof which stays cold because it extends beyond the side of the house.
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An ice dam forms when the roof over the attic gets warm enough to melt the underside of the layer of snow on the roof.
For example say our house is 40 feet long and 30 feet wide.
Mine took four hours to melt a nice path for the snow to melt and run past the ice.
Next go up on the roof and put ice melt socks vertically one end onto the gutter and the other end up the roof slopes spacing them every 3 feet.
If you see ice on the edge of the roof and the temp is climbing and there is snow on the roof above the ice dam turn it on.
That equals to 2 3kwh per hour or almost 56kwh per day of continuous operation.
2 a bucket bag of calcium chloride ice melt.
Secure shingle clips to roof shingles using a flathead screwdriver making sure to align them in a zigzag pattern.
Using a roof rake remove snow 3 4 feet from the edge of your roof being careful not to damage the roof covering or to allow snow to build up around walking paths or to block emergency exits.