Simon Barker:
The intention is that you can isolate the whole installation with one switch, rather than having to flip a whole bank of breakers. If there is a main switch in the distribution board, then that is the isolator. Otherwise, there should be an isolator before the DB.
If it's a DB, then that implies that it's just one part of a larger installation. In which case, is there an isolator at the origin of the supply?
Graham Kenyon:
Don't forget, in accordance with BS 7671, isolators for LV systems must disconnect ALL poles (including Neutral), unless the supply is a TN system (TN-S or TN-C-S) in which isolation of the Neutral is not always required.
We're about to take you to the IET registration website. Don't worry though, you'll be sent straight back to the community after completing the registration.
Continue to the IET registration site