I am having a new bathroom installed and an extractor fan is required. The supply to the bathroom is on the upstairs lighting circuit from an RCD protected 5A MCB in the consumer unit and the fan will be fed from this circuit. There is a 3 pole fan isolator switch outside the bathroom but the extractor fan instructions say it should have a 3A fuse. Adding an FCU to feed just the bathroom makes it all over complicated. Since the whole lot is fed from a 5A MCB, would this not make the addition of a 3A fuse unnecessary?