I would use a DPDT switch with block heater connected to center contacts.
Somthing like this: Leviton 1286-W 20-Amp 120/277-Volt Toggle Double-Pole AC Quiet Switch
Can't find the "Introductions Forum", but wanted to say hello, to get message off the top of the screen.
I kept stumbling across GJB when searching for info on various projects.
Hello