[Dave] built a controller that lets him boil two kettles at once when brewing beer. The setup uses electric heating elements in each of the kettles. We prefer to use gas as it’s a bit easier to control temperature. But an electric system like this can be used inside during the winter months while propane is relegated to the outdoors. The other thing that immediately comes to mind is partial mash recipes that require steeping in one kettle, then sparging (rinsing off the grains) with water of a different temperature. That kind of thing is a snap since the two are controlled individually by the trimpots on the front of the control box.
Inside you’ll find two 220V solid state relays. The box itself plugs into the 220V outlet in his basement which is normally occupied by his clothes dryer cord. So as not to blow a fuse, the MSP430 chip driving the relays switches back and forth between them rather than turning both on at once. The system uses entirely manual control, but it should be an easy modification to add a thermocouple and PID algorithms if so desired.
After the break [Dave] shows off the system in a video clip.