I need to fit a 45A breaker for my shower, but my current MCB only allows up to a max of 40A. Do I have to install a new circuit board, or is there another option
Electric showers are not recommended where the maximum supply fuse and/or CU Isolator rating is 40A as this is only really enough for 1 Ring Main, 1 or 2 Lights and 1 Boiler.
I would suggest speaking to an electrician about upgrading to at least 60A.
Note that since the begining of this year, electric wiring in kitchens or bathrooms must be done by an "approved person" or it attracts building regs inspection.