The existing fused switch stays as it is with a 3A fuse, a blank plate is fitted over the old programmer position.
The only time another isolator is fitted is if the boiler is not near the fused switch in which case an isolator that isolates all lives and neutral needs to be fitted within reach of the boiler to allow it to be serviced safely.
A skilled electrician or heating engineer should be able to alter this about easily.
The only time another isolator is fitted is if the boiler is not near the fused switch in which case an isolator that isolates all lives and neutral needs to be fitted within reach of the boiler to allow it to be serviced safely.
A skilled electrician or heating engineer should be able to alter this about easily.