I don't see an obvious get-out clause for 421.1.7 like there is for 411.3.3. Maybe IT equipment (being generally free of a.c. motors and frequently operated switching devices) isn't particularly prone to nuisance trip AFDDs,but I share your concern.

I guess another option would be to hard-wire the rack (e.g. replace the socket with a rotary isolator), make it a 3-phase socket (421.1.7 only applies to single phase) - it's fine just to pick up one phase at the plug if that all that's needed, or perhaps replace the fixed socket with a box, a short length of dangling flex and a BS EN 60309 connector ... by BS 7671 definitions that would seem to be classed as connector rather than a socket outlet (but I can see a debate about that).

   - Andy.

I don't see an obvious get-out clause for 421.1.7 like there is for 411.3.3. Maybe IT equipment (being generally free of a.c. motors and frequently operated switching devices) isn't particularly prone to nuisance trip AFDDs,but I share your concern.

I guess another option would be to hard-wire the rack (e.g. replace the socket with a rotary isolator), make it a 3-phase socket (421.1.7 only applies to single phase) - it's fine just to pick up one phase at the plug if that all that's needed, or perhaps replace the fixed socket with a box, a short length of dangling flex and a BS EN 60309 connector ... by BS 7671 definitions that would seem to be classed as connector rather than a socket outlet (but I can see a debate about that).

   - Andy.