Always remember that the sole purpose of a breaker (Main or Circuit) is to protect what it is feeding. In most cases the breaker is feeding an electrical wire (Circuit), except for the MAIN breaker, which protects the electrical BUS bars in the breaker box to what the breaker box, is rated for (i.e. 100A, 200A, etc.).

If you did put a larger BREAKER on a smaller gauge wire (NOTE: The higher the # the smaller the wire) then you have put that given circuit at risk of getting the wire hot which could cause it to melt or worse, catch on fire.

So with that being said, you should NEVER increase the breaker size unless you are FOR SURE that the wire meets the gauge requirements for the circuit.

GONK has the correct gauge sizes above...