Tuesday, January 10, 2017

Snow Melt Cable

I have been hunting for a solution.  There are a surprising number of companies that sell cables or mats that go inside the asphalt or concrete, and you can have the cables installed after the fact by cutting trenches in the surface.  For 600 feet that sounds expensive.  I suspect that just a melting cable just under the edge of the pavement would do the job.  This is advertised as 12 watts per foot.  There is a 240 VAC 428' length listed, which would get me to the worst part.  This would get most of the way down the driveway; a heavy gauge 240 VAC extension cord would get the rest of the way down perhaps in some waterproof conduit.  This is a bit of money, but it would end plowing, and greatly enhance house value.

According to Google Earth a path along the driveway from garage to base is about 879 feet.

As the crow flies, 659 feet:
Since I will need two sections, I could use one 428' segment to the big turn along the pavement, and a 240VAC line from garage to the big turn, and the 428 heat cable to the base, which is 424'.


  1. This is going to cost a lot more to run than your LED lighting, but less than the lifetime cost of a tractor and snow blower.

    1. Right now, being able to leave the house would be worth higher electric bills. Maybe two runs, one on each side of the driveway. That's 24 watts per foot. It doesn't have to be instaneous. Even waking up to a clear road would be worthwhile.

  2. I suspect that a single run of this cable isn't going to melt the width of a driveway.

  3. Look into a 3-phase system. More efficient.

    If not that, then a tractor (min of 30 pto HP) with MFWD, filled tires, chained up, and a power angle blade with a polyurethane wear edge to scrape the asphalt without damage. Never let it build up, and it becomes an easy task.

    If you want more SME hit me by email.

  4. You could run the two lines as 'tire tracks' down the driveway. My (much smaller) driveway slopes about five degrees and faces East so I often just shovel the lines behind the tires and leave it at that.

  5. If you are going to do two runs, make them match the track width of your vehicles. But as you suggested earlier, if there is any sun at all once some blacktop is exposed to light the rest of the drive will clear itself quickly.

    As long as one of the wires is on a drivable path for a tire, it will allow you to get up the drive with anything that has a limited-slip differential or traction control.

    I calculate that the "extension cord" for the lower section would need to be #6 copper or #8 aluminum to be under 5% voltage drop. I'd suggest hard-wiring it. For heating loads the breaker and cable need to be sized for 125% of the rated load.

  6. Feasibility analysis:

    A 879 ft path 8 feet wide is 7032 sq ft. A mere 4 inches of snow is 2344 cubic ft. The internet suggests this will weigh between 3 and 12 pounds per ft3.

    Let's suppose 4 lbs/ft3 = 9375 pounds of frozen water. With a heat of fusion of 333.55 J/g (and 453.592 grams per pound), this will require over 1400 MegaJoules of energy to melt. (Not counting what you need to raise it to the melting temperature in the first place.)

    1 watt is 1 J/s, which is also 1 volt-amp. Let's say you'll give it 8 hours to melt, which is 28800 seconds. So you'll need about 49 KiloWatts of power. That's over 4000 feet of 12 w/ft cable. At 240 volts, you'll need 200+ amps of current, which might exceed the capacity supplied to your entire house. At $0.10 per kilowatt-hour, I think it will cost about $40 (each time) to run.

    That's for 4 inches of fluff.

  7. One of the potential problems with melting the snow like this is that unless you keep it running until it has not only melted, but all remaining moisture has evaporated, it will turn into a thin sheet of ice. You can't rely on the sun to evaporate it, I suspect. I doubt the blacktop would remain warm enough to allow it to stay liquid. You could spend money to make your driveway totally impassable.

    You need to find other people who have had success with this idea, before spending money on it. Actual data is needed.

    Most houses built in the last 30 years have 200A service, at least in the Bay Area. Upgrade to 300A is feasible here. They might run 3ph to your house (garage), since it's not urban. Ask supplier about cost (wiring). (3ph tooling! Yay!)

  8. Obligatory relevant XKCD: