Problem with Resistance Wire
Hello Everyone, This is my first post here so if I violate any rules I am sorry. I have a question with resistance wire, specifically Kanthal A1 resistance wire. To my knowledge these are treated basically like big resistors. I have a the problem drawn up here. Compound Resistance I took a class on basic electronics but it has been a while. I would hope that someone could look over this and make sure I am doing my math/theory right.
My Goal is to have a heating element that will push out around 3000 Watts.
Total Voltage=240 Volts, Total Resistance of Circuit=18.92 Ohms, Total Amperage of Circuit=12.68 Amps, Total Watts=3043
R1=18.025 Ohms x 12.68 amps =228.56 Volts = 2898 Watts (25 Meters)
(R2 and R3 in Parallel)
R2=1.8025 Ohms x 6.34 amps =11.43 Volts = 72.46 Watts (2.5 Meters)
R3=1.8025 Ohms x 6.34 amps =11.43 Volts = 72.46 Watts (2.5 Meters)
So now my question. Kanthol Resistance wire should not be heated to over 2.4 Watt/cm. Through my calculations R1 cannot go above 3,018 Watts. (R2 and R3 are in parallel and have more than enough surface area.) Is this how electricity works in compound circuits like this? I am assuming that each wattage resistor is added? Thank you for checking this out.
Edit: This is for a Kiln. Each "resistor" is a strand of wire. Kanthal I am using is .721 ohms per meter. If this is stupid and there is a better way I would love to know. Thank you.
Posted Feb 15, 2015, 2:20 AM UTC · edited
Out of curiosity, what does each resistor in the diagram represent, and what are you trying to do with it? The math works out, but I'm drawing a blank for exactly what you'd need 12.5 meters of heating wire for, especially with two additional much smaller elements in parallel with each other.
I am sorry this is for a kiln! I edited my post. Each "resistor" is the actual wire itself. I am trying to use 30 meters of Kanthal A1 as efficiently as I can. The Kanthal wire is .721 Ohms per meter for 14 AWG. So It would be 21.63 Ohms for a single strand of 30 meter wire. 240V/21.63 Ohms is only 11.1 amps. So it would only be 2664 Watts. If I reduce my main wire, I get less resistance and more amps. But I have to watch out for the surface area of the wire getting too hot and reducing life of the wire. In the Kanthal manual it says 2.4 cm/watt. I figured I would add the other wires in parallel to squeeze out some more watts. Kind of a give and take relationship. I want to make sure the math is correct though because I am not too sharp when it comes to compound circuits.
I understood each resistor was a representation of a length of wire. A kiln makes sense for this application. And now the parallel areas make sense. I wanted to be sure they were there on purpose and not a misunderstanding. I've seen a lot of people assume that a resistance between V+ and the main circuit is in parallel with a resistance between the main and ground.
So it looks like this circuit should be fine.
Ok thank you for looking it over, I really appreciate it.