We have two circuit breakers, a 70amp double pole and a 50amp double pole. The 70 amp double pole seems to be fused onto the silver bar and unremovable. The 50 amp is removable. The 70 died out on us. Can we just replace the 50 with a 125 and attach the wires from both the 70 and 50? or do we need to replace the whole box? This is the main switch for the whole house. There are 2 other boxes with the individual breakers for fridge, oven, etc. Thank you for your help!

One more consideration---- the output lugs of the 125 must be able to accept two output wires. One more consideration---- the output lugs of the 125 must be able to accept two output wires.

The point is, it is highly likely your 50 amp circuit uses wire sized for 50 amps and your 70A circuit is wired for 70A By putting both wires on a 125A breaker, you are exposing either (or both, depending on how you look at it) circuits and therefore the wire to as much as 125A continuous. This is a good recipe for a wiring fire inside the walls. The point is, it is highly likely your 50 amp circuit uses wire sized for 50 amps and your 70A circuit is wired for 70A By putting both wires on a 125A breaker, you are exposing either (or both, depending on how you look at it) circuits and therefore the wire to as much as 125A continuous. This is a good recipe for a wiring fire inside the walls.