I'm building a reprap printer. I have a sheet of aluminum about 8x8" to use as the print surface, which must be heated to prevent problems while printing. </background-info>
My controller board can handle a maximum of 60V @ 11A, before either the PTC fuse trips or MOSFET overvolts. I'm not changing these components, so whatever solution I find has to fit within these constraints. I have 12x 1 ohm, 10W aluminum chassis-mount resistors that I intend to abuse as heater elements. I'm trying to find the most efficient way to parallel/series the resistors and what supply voltage to use to draw the most power. Existing power supplies I have are either 12V @ 18A, or 24V @ 6.5A, and I would prefer to not purchase another one if possible.
Exceeding the wattage of the resistors temporarily is perfectly acceptable, because I'm only shooting for a target temperature of 65-110C (depending on the plastic used). Any solution I'll be happy with should hit that temperature within 10 minutes or so, so pushing 25W through a 10W resistor in that time won't really cause them damage. And if it does, meh, they're a buck each. After the platform is at temp, a microcontroller will cycle the power of the resistors to control the heat.