Electrical – DIY Oven heater


I was not exactly the best studier in my class, when everything was explained, but I suddenly got interest in electrical engineering and now – how heaters are made.
I may not attempt to make one, before I educate myself a little. But it is just puzzling me and I cannot rest without knowing the answer – How are oven heaters made.

  1. If you take a copper tube or kanthal/nichrome wire and give it a voltage so that they heat – isn't that short circuiting the voltage source?

  2. How to determine what wattage is going to be needed to achieve the desired temperature? Let's say I want to achieve temperature levels up to 200o Celsium. This means the tube/wire itself must be somewhat hotter so that it provides this temperature in an area of say a pack of cigarettes.

I know that the diameter (thickness), the material, the length matter as well as the way they are formed – these factors are remotely related to the resulting resistance and wattage needed, but I am unaware of the right formulas to calculate them based on my expectations.

Best Answer

The heating wire has a finite resistance and you can use ohm's law to determine how much current will flow through the wire given the voltage. You can also calculate the power using voltage times current. The power supply needs to be able to supply the current without damage, but as long as it can source the calculated current, you will not have a "short circuit" situation. Be aware that depending on what the wire is made out of, the resistance may vary substantially with the temperature.

Calculating the resulting temperature involves doing an energy balance calculation and requires the thermal characteristics of the enclosure the heater is mounted in. Generally, heaters are capable of generating much higher temperatures that are desired and a thermostat / temperature sensor is used to turn the heating element on and off to regulate the temperature. Where accurate temperature controls are needed, a thermistor, thermocouple or other temperature sensor is used with a PID controller to regulate the temperature.