Heating Cable Question

Discussion in 'Shop Talk' started by Jennifer L., Dec 20, 2006.

  1. Jennifer L.

    Jennifer L. Well-Known Member Supporter

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    I'm installing an automatic watering system in my rabbit barn. It's going to service about 100 cages. In this area you have to have something to keep the lines thawed, so I've gone with heating cables in the lines. The place where I bought the cables from say you can't splice the cables (no problem understanding that one, given that they are going in water) and that you can't shorten them. My question is, why can't they be shortened?

    The catalogue says this about them:

    "Each combination of lengthes and wattage below prvides 5 walls /ft of cable, which is adequate to protect water lines down to 10ºF/ For protection to 0ºF, install two cables into the line. CAUTION: Heat cables must not be shortened or spliced."

    Are the heating elements of each cable sized differently?

    I'm not interested in shortening any of the ones I got, but just wondered why they say they can't be.

    Jennifer
     
  2. ace admirer

    ace admirer Well-Known Member Supporter

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    the riddon cable has a resistance per foot. its designed to pull a limited amount of current for a length. if the length were to be shortened, the total resistance would go down, current would go up. the shorter cable would get dangerously hot.
     

  3. Cabin Fever

    Cabin Fever Life NRA Member since 1976 Supporter

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    The reason for this is that a heating cable is actually a loop of wire. One end of the wire goes to power and the other end to ground. When you splice or shorten the loop, you cut the loop and no longer have continuity. In other words, picture an immersion coffee heater or an electric heating element on your range or oven. All of these examples are “loops.” If you cut the loop (to shorten), you interrupt the flow of electricity and the heater no longer works.
     
  4. agmantoo

    agmantoo agmantoo Supporter

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    There is on the market a heat trace cable that can be cut to any length and the end of the two wires do not get spliced together. The conduction is across the carbon material between the two parallel wires. I think the manufacturer is chromolox.
     
  5. cfabe

    cfabe Well-Known Member

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    On "normal" heat cables, if you shorten them and do re-connect the wires at the end, the resistance will be lower, they'll draw more current and will overheat and burn up.
     
  6. agmantoo

    agmantoo agmantoo Supporter

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  7. Jennifer L.

    Jennifer L. Well-Known Member Supporter

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    OK, that makes sense. Here's another question about them: Do you need a special plug to rig a heating cable? The cables I have do not have plugs.

    Jennifer
     
  8. ponyboy123

    ponyboy123 Well-Known Member

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    i have about 2 miles of heating cable run around my mink farm for auto watering system. The rolls I bought came in 912' lenght and came with the same warning on cutting and splicing. I would not recomend shorteninh these wires because it will over heat and perhaps burn up, as far as lenghting them, not a problem. I used electrical butt connectors and water proof shrink tube, used in submersible pumps. The big draw back is that the wire will not heat as well with the extra length. My longest runs are the first to freeze up when the temp drops to minus 25 or 30 degree celcius. What did u use for watering nipples or did u go with water cups? No special plug needed. My wire is rated for 220 volts so I ran in 10 double pole 15 amp lines(1 for each barn). And they run off 240 volt rated water proof switches. Make sure u take care in getting as good of grounds as u can when dealing with power and water. Ground to building, tank, power boxes and bury a grounding plate 2' in the ground for extra protection.
     
  9. Jennifer L.

    Jennifer L. Well-Known Member Supporter

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    Hi, Pony. Thanks for the information. I went with some valves from Klubertanz http://www.klubertanz.com/ called Dew Drop Valves. I'm screwing them directly into the PVC and hope that they won't leak on me. If they do I figure I'll be ordering the pipe saddles and redo everything with them. I thought about the water dishes, especially would be useful if things really froze up so each cage could be easily hand watered, but decided not to spend the extra money this year.

    I had an electrician wire the box into the barn, but the advice on the ground is always good. You are right about water and electricity. I don't mind running my own lines inside the buildings, but like to have someone who knows more about it than me work off the entrance.

    I've been running on luck with the weather--normally here we should be really cold, but the last two weeks have been like early November, not December. Have to get this done, though!

    Jennifer