I Calculated for 3 wire sizes, but only use the 28AWG as it supplies enough heat. Even a 30AWG wire wire would do OK, but being smaller, its harder to work with.This is NOT a Project I recommend Anyone attempt to make. This is Posted here, Only to show "How I love to Experment".
I Designed this up for a friend of mine as an alternative to the Expensive, commercially designed systems.
He has a large enclosed Sundeck over a garage, And even though he added fiberglass insulation under it, this floor gets very cold in the winter months. However this is "NOT a Legal system" to be used anywhere And Does NOT MEET ELECTRICAL CODES.
Since this is NOT here as a Construction PROJECT, NUMEROUS Details have been OMITTED. So PLEASE DO NOT ATTEMPT to MAKE THIS!
The wire we used to make this is a 28AWG, High Temperature Enamelled Copper wire. The same type as used in winding most Power Transformers. With Continuous Power, this works out to about 5.3 watts of heat per Square Foot of his floor.
The Floor is first prepared by pouring a thin layer of Thin-Set Concrete. Than carefully laying out the wire and the Diodes for temperature Detection using my Temperature Controller.
After Testing it to make sure all is OK, Another layer of Thin-Set Concrete is applied over the Wires and diodes. The Thin-Set Cement adds Extra Protection, should the wire break and cause arcing.
When the Thin-Set is FULLY DRY a hardwood floor is put over the surface for appearance.
The Temperature Controller I designed, detects the small voltage change across the 4 diodes and cycles the heater On & Off as needed. It can be adjusted over a considerable temperature range. This Schematic is shown below.
I Use Simular, Smaller heaters in my Vegitable Garden to keep it from freezing during the winter. For these heaters, a wire is Laminated between Two sheets of 1/8 inch Mahogany Plywood using Contact Cement, and this produces a Heat capacity of 50 Watts for a 2 foot by 4 foot area. So that is only 6.25 Watts of heat per Square Foot.
When running Continuous, It Just gets LIGHTLY WARM to the touch and does NOT Burn or Discolor the wood. I give it a topping of wood shavings and glass to keep heat in and water out. And it Never runs continuous, even at -20 Degrees Celsus.
It is Nice to have Fresh Carrots, Parsnips and Beets that I can dig up ALL Winter Long. And the Amount of Heat & Electricity is Quite Small to accomplish this.
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