I have worked in powder coating for 16 years. I built several ovens, 1 batch oven and 3 continious ovens.
The batch oven is 12 ft wide, 24 ft long, tall enough to drive a forklift in there with several racks of parts. We fill the oven with as many racks of parts as it will hold. Close the doors, turn on the heat, when the temperature reaches 240 degrees it runs for 20 minutes then turns off. In about 30 minutes or so it will be cool then the parts will be loaded onto a tractor trailer truck after inspection.
The continious oven is 2 ft wide, 4 ft tall, 80 ft long. The continious oven can do 10,000. small parts per hour to about 100 very large parts per hour. Temperature inside is usually 240 degrees F.
Production decides on the set temperature of the oven according to the spec sheet of the manfactures power. Each power has a cure time and a cure temperature. Some companies specify the type of power they want us to use on their parts. If the spec sheet says 240 degrees for 20 minutes that is how long it has to stay in the oven once the parts have come up to full temperature. We can attach heat sensor to parts to find out when the metal has reached 240 degrees F then we time for 20 minutes then the oven gets turned off then it cools down.
At the moment we are powder coating shelves for Dollar General at the rate of a tractor trailer truck load every day. Sometimes we powder coat wheel weights, some times motor cycle frames, sometimes city lamp poles, sometimes generator frames and more.
We checked into buying ovens from manufactures but they want several times what it will cost us to build our own. I built the 80 ft continious oven in 3 months and did most of the work all by myself. The batch oven took about 2 months. Heating elements are 240 volts $1000 each they are 4 ft long 1 ft high. 4 rows of heating elements down the middle 2 rows each side. Manufactures price was $450,000. and delivery time was 1 year for a ready made oven. I built this oven for much cheaper in 3 months. I used Fuji programmable temperature controllers $250 each only need 3 controllers to control 3 sections of the oven. Heaters are wired in banks, first, middle, and last. It also has 20 on/off relays rated 240 VAC 60 amps each. The chain conveyor system runs along the top of the oven. It is really very simple.
