'Garage' (but it isn't) consumer unit, does it reqire a main switch?

[Chris Green]

We have a small brick built tack-room and two loose boxes which have mains power fed to them from a 20 Amp RCBO in the garage consumer unit.

The feed comes into (another) small CU on the wall in the tack room, this currently has a main switch and three MCBs feeding sockets and lights.

Is there actually a requirement for the sub-CU in the tack room to have a 'main switch' that turns off all the circuits in the tack room? I'd like to replace it (the small CU that is) with an even smaller one that only has space for 3 MCBs, quite sufficient if there doesn't have to be a main switch.

[John Rumm]

It would meet the requirement of protecting the smaller capacity cables as they transition from the submain. So it becomes just a MCB enclosure rather than a Consumer Unit as such.

I can't immediately think of a regulatory requirement that it has its own isolation, although personally, I think it would be better design to have a switch there in case someone unfamiliar with the installation should need to isolate in an emergency or at the very least, a label indication where the nearest point of isolation is.

[ARW]

A question like that can start electricians arguing.

But I am a firm believer that the main switch on the supply DB to the sub DB meets all the requirements for isolation.