Have a Marley PLF 1504 and want to replace an older unit. The PLF 1504 has: 1 single green wire (w/twist nut) and a red wire and a black wire (in a twist nut) and a red wire and a black wire (in a crimped cap)(both ends of the heater are the same) I have a black wire and white wire for power. When I attached my white power to the single green AND the black power wire to the red and black wires (in the twist cap), I blow the breaker! What is wrong here? Thanks

Is this a direct replacement - same models? Is the voltage the same for both units? Usually the Green wire is the ground. The White wire is the common, or neutral. And the Black wire is the hot. I hope this helps.