Regarding my comment about 2-mod enclosures, they don’t have neutral bars.
Edit- so you need a device with four terminals rather than three with a flying lead for the neutral, such a most AFDD have.
So you cannot fit a single pole RCBO or an AFDD in a 2-mod enclosure alongside an existing fused switch, fuse board or consumer unit, because there is nowhere to terminate the neutral flying lead to transition to sheathed cable to get back into the existing equipment, so you need a garage CU or similar and generally they are just too big to fit into the required position.
Then before you know it you need to be replacing everything or trying to compromise on what is ideal.
Regarding my comment about 2-mod enclosures, they don’t have neutral bars.
Edit- so you need a device with four terminals rather than three with a flying lead for the neutral, such a most AFDD have.
So you cannot fit a single pole RCBO or an AFDD in a 2-mod enclosure alongside an existing fused switch, fuse board or consumer unit, because there is nowhere to terminate the neutral flying lead to transition to sheathed cable to get back into the existing equipment, so you need a garage CU or similar and generally they are just too big to fit into the required position.
Then before you know it you need to be replacing everything or trying to compromise on what is ideal.
