Out of a moment of whimsy, I decided to build a heating system for a toilet seat. A web search shows that these items are very popular in Japan, and Kohler has a commercially available unit for under $100. However, its size was not right for our use. As a result, I assembled a unit from scratch.
Photo of the heaters installed and the wires embedded with epoxy into the molded wood.
First, I acquired some foil heaters from the Minco corporation that were each about 20.1 ohms of resistance (part no:HK5427R20.1L12B). The cost is unknown. They are good to more than one Watt per square inch, so I had plenty of margin on that parameter. I then purchased a new seat for about $15. I selected a "molded wood" type opposed to a plastic one, as I suspect that its thermal conduction is better. I also think it is easier to machine and cut. Onto the sides I attached the two Minco Foil heaters, which I wired in series to a small electrical jack on the edge of the wood. I embedded the wires in a groove that I made with a circular saw, and then filled the groove with epoxy to replace the structural strength of the material that I had removed.
Detail of the wires embedded in epoxy and the small electrical jack on the edge of the wood.
After this was assembled, I then spray painted the whole face to restore the uniform appearance. This resulted in a very clean look, with only a small silver jack visible from the side. This jack accepts a plug for the electrical power.
View of the finished unit.
I used an AC transformer rated at 16Vac. With the 40 ohm load, this results in about 3.2 Watts per foil heater. This very small amount of power heats the foil side to a noticeably warm temperature (about 90F), but is cooler and more evenly distributed on the top side of the seat. I measured the total power draw with my "Kill-A-Watt" power-meter, and it was only 11 W (about 4 W lost in the transformer), or about one penny per day of cost to run this device.
Photo of the finished installation. Note the GFCI outlet that I had installed in the wall for this project.
After a few trial months, the transformer will be hidden.
View of the installed seat. Note the GFCI protected
I installed just next to the toilet. After a few months use
winter, I will decide on the right voltage, and will replace the large
transformer and wires for a more clean look.