This 🔥 idea had been used for electric heating 12' X 13' X 20' warehouse in severe weather. Simulation shown in high 240 volt mode. The micro ohm resistors added to run the simulation.
The two single pole double throw switches is actually one double pole double throw knife switch to select high 240 volt or in milder weather 120 volt power.
The 3 SPST switches represent fuse box or circuit breaker switch to turn power ON / OFF.
Materials:
Two 1" x 8" x 12" slate slabs drilled with four 3/8" holes so the threaded 3/8" rods and 30" long 1/2" pipe spacers hold the slate slabs parallel to make the box shape frame. 20 small holes are spaced to allow 20 of 30" long coiled 13 gauge galvanized iron wires used for resistance coils ( about 1,000 foot of wire or 25 pounds of wire). Resistance coils are all wired in series.
If a 3800 watt electric heater on 20 watt fuse protected circuit at operating temperature. Our 240 volt electric heater sends 15.8 amps through 15.18 ohm of wire at operating temperature.
Using a 30-amp circuit is suitable for up to 5,700 watts. The standard circuit cable for 20-amp circuits is 12-gauge cable; 30-amp circuits need 10-gauge cable.
An adequate cabinet or cover safeguard against line voltages and high temperatures remains to be solved.
