The voltage of your power supply affects the kiln's firing speed.
When you buy a kiln that fires too slowly, check the kiln’s voltage. It is listed on the electrical data plate located on the side of the switch box. Make sure the voltage matches that of your building. A 240 volt kiln in a 208 volt building will fire too slowly.
Sometimes the heating elements of a used kiln do not match the voltage listed on the electrical data plate. This is because the elements were changed to suit a different voltage. If you suspect this of your used kiln, call the manufacturer and ask for the wiring diagram. It will list the resistance of the elements, which you can check with an ohmmeter.
Arnold Howard Paragon Industries, Inc.