Originally Posted by dalebra
IMHO you should never replace a 15 amp breaker with a 20 amp breaker without upgrading the wiring to 12 Awg.
20 Amp breaker and 14 Awg size wire is a violation of the NEC. (National Electrical Code)
If you simply replace the breaker, the wire can overheat and ignite the building from inside the walls.
Actually it is allowed and done all the time when installing a new panel. When we would install a new panel, and new meter box we would jump the meter fittings with #10 solid wire. Running the whole house.. they were uninsulated and open but it can carry the load with no issue. Using 20 amp breaker on 14 wire is allowed when installing a new panel, it will not draw enough power to be an issue.