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Electrical floor heating kits run US$10 to $15 per square foot, but bulk wire only costs $2.50. With the controller, you're still running under $4 a square foot. I have a construction background, but not electrical. Are there any good books out there that takes a novice through the steps of buying just the parts and making one's own?

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While you can fit your own heating kit - you should buy the proper components. –  ChrisF Mar 11 '13 at 9:04
    
@ChrisF: It looks like he's asking exactly about that - how to buy "proper components" and craft the heating system from them. –  sharptooth Mar 11 '13 at 10:39
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Just a fore warning, any advice you receive on this subject may be dangerous. It doesn't hurt to seek the advice of a professional when dealing with something that's designed to heat up an electrical coil, but not quite burst it into flames. –  BMitch Mar 11 '13 at 12:10
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to clarify: is the "bulk wire" to which you refer labeled as resistance heating wire for subfloor heating systems, or are you talking about wire intended for electrical transmission (i.e. "standard" wiring)? –  mac Mar 11 '13 at 17:31
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My interpretation of "but bulk wire only costs $2.50" suggests that Ralph is trying to shortcut and use regular wire. That spells house fire to me. I would think that if regular wire got hot enough to be an effective heat conductor you'll run the very serious risk of catching something ablaze. I don't think this is something you should try to concoct yourself, especially out of non intended parts. –  Peter Mar 18 '13 at 19:24

2 Answers 2

Just don't. This is clearly the best answer.

If you really want to cheap out perhaps you could buy a complete kit with just one square foot mat, analyze the wire used, and try to source a designated radiant wire of similar dimension and resistance. Then fold and spindle that in a similar way to the mat squares.

Remember your fire insurance likely excludes work done in flagrant violation of the building codes. Use of regular copper wire, while possible, is just not advised.

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When wire is used for heating, it is important to ensure either that the wire is of very uniform thickness, or that it is constructed of an alloy whose electrical resistance decreases with heat and fed by a device that will limit current. If those conditions aren't met, the thinner portions of the wire are apt to heat up more than the thicker ones; if resistance increases with temperature, that effect will cause hotter parts of the wire to produce more heat than cooler ones, thus becoming hotter still.

It's possible that ordinary wire may "work", but it may be difficult to ensure that there's no danger of the hottest spots getting unacceptably hot. Wire that is designed for heating must be made more precisely, and is more expensive as a result.

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