They are water heater timers specifically made for 240, and I've use one on 240 for several years. Just can't remember if the white wire goes to 3 line, or A.
yeah what rives said you should put a 15amp braker for that wire at least do that brakers about $7-10 bucks..running on 240v the wires going to the lines on timer are both powers running 240v only so from what i know red or white can go on 3rd line if the wires are coming from the double braker.they both are power just make sure you ground both the sub panel to the timer this should be the bare coper wire to the frame of timer and make sure the main panel is also running ground wire to frame of sub panel or to bus and from bus to timers frame its the screw by its self tipicaly color green screw
hey bro good luck hope your up and running soon,DG