My house MCB most of it harden already, stuck, so difficult to pull down or push up. My electrician advised me to change all even though some are still good. And he suggested all change to 32A. I have 10, 20 and 32A. I am worry about his advice to change all to 32a and if the cable/wire can take load and what is the danger of doing so.

It is time to get some advice from others like you and be sure and if I can diy or just let him do it. See picture of my DB and the 3 types of MCB.

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Your electrician want you to change house is it? All 32Amp, if wires are 1.5mm, use until wires burn the MCB won't trip. Usually they will put 20A for socket, and some will use 32A for a/c and heater, but 20A is good enough because 2.5mm can't supply 32A load for long period, and now a/c don't have such high spike.

Light, use back 6A or 10A.

Best check the old MCB, and do direct replace.