Originally Posted by clasact
its 240 I ran two 12-2 wires on 30amp breakers
Whoa, first of all you cannot use 12 gauge wire on a 30 amp breaker! Second, are you running two heaters or just one? Why do you have 2 12-2 cables? If this heater is truly only 240 (no 120 volt fan or controls etc) then you only need one cable. Also, at 1250 watts this could easily be ran on a double pole 15 amp breaker (with your 12-2 wire). 1250 watts @ 240 volts is about 5 amps.
First thing you should do is change out the 30 amp breaker for a 15 amp double pole. Unless you plan on adding more heaters to this circuit, 15 amps should be enough for 2 heaters of the same size.