I've been asked to finish a job that was started a few years ago the only problem is when the job was started the 16th edition regs were in place, So the consumer units that were fitted at this time are also only up to 16th edition regs and so some of the circuits have no rcd protection. My idea now is to change some of the mcb's to rcbo's and move some onto the rcd side of the consumer unit. But what i'd like to no is how many can i put onto the rcd side and how many do i have to change to rcbo's. Obviously for the customers sake i'd like to keep the amount of rcbo's to a minimum because of the cost. There are 9 circuits in total but 6 different houses so it could get a bit expensive.