Power for roof de-icing cable


Old 11-03-09, 10:27 AM
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Power for roof de-icing cable

We had a big problem with ice damming on the east side of our roof last winter. So yesterday I installed a heater cable. It's 200 feet, 1200 watts, 120 volts.

Today I discovered that all of the nearby outlets are on the same 15 amp circuit as our fridge and a microwave. It looks like the 1,000-watt microwave draws up to 9 amps. I couldn't find any specs for the fridge, but it and the rooftop cable certainly can't share a 15 amp circuit.

There is an unused laundry room outlet that seems to be the only device on its circuit, also 15 amps. There are definitely no heavy load devices. This outlet, inside the house, is 16 feet from the plug on the heater cable's six-foot power run and seems to be the closest power point aside from outlets on the already loaded circuit.

It occurred to me to:
-- Replace the current laundry room outlet with a GFCI
-- Get a 20-foot heavy duty 12 gauge extension cord rated for 15 amps, 1875 watts
-- Cut off the extension cord plug and run the wire through the house wall. Replace the plug. Secure the cord both inside and outside the house.

This would provide the rooftop cable with a dedicated circuit. To indicate when the cable is turned on, I'd turn on the laundry room ceiling light which is on a different circuit.

If the rooftop cable works this winter, next spring/summer I'd have an electrician run a line from the laundry room outlet through the wall and install a proper outdoor receptacle with a pilot light switch inside the house.

Does this make sense? Any advice -- aside from checking circuit load before installing a fixed heavy load device like this cable?

BTW, the point where the cable would plug into the extension cord is at the house wall right under the eaves and thus sheltered from rain/snow.

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Old 11-03-09, 11:06 AM
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You can't cut off the end of an extension cord and run it through your house walls. Wiring installed in the interior portions of your walls must be listed for such use. An orange extension cord from the hardware store would certainly not meet this requirement.
Old 11-03-09, 12:03 PM
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The alternative would be to get a 75-foot heavy-duty extension cord and run it around the house to the other outdoor outlet. That outlet is on the same circuit as living and dining room outlets. The heaviest user is the TV which is 140 watts. So TV is a bit over 1 amp. The rooftop cable is 10 amps. So a couple of lights would take me to 12 amps -- the max circuit load recommended by the cable manufacturer. But would there be too much power draw or power loss in a 75-foot extension cord?
Old 11-03-09, 01:31 PM
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The only proper solution is to install a GFCI protected receptical where the heating cable can directly plug in to. Use a bubble cover. I would put it on its own circuit.

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