RCD Protection at Data Cabinets

This does bring out a point from BS7671, which is the blanket requirement for RCDs for sockets up to 32A. In an installation such as this with supplementary bonding to earth, the RCD has exactly zero use!

But supplementary bonding won't protect against instances of direct contact - e.g. from a damaged flex - where a 30mA RCD will provide some benefit. I've certainly seen flexes trapped in 19" rack doors and pulled around sharp edges of some of the metalwork before now. Certainly they're the situations it's easy to avoid with a bit of care - a policy of properly securing flexes and only allowing access to (authorized) persons with a bit of nous would seem to do - but we can't really assume that without a risk assessment to say that's the case. A lot of IT types, which very technical in some ways, really don't appreciate the hazards of mains electricity.

Same with plug and socket-outlet. They're all just isolators.

Sorry, but I've got to disagree with that. Plugs & sockets mean that IT technicians and change the power supply arrangements safely. Bare in mind that when something goes wrong with live (i.e. customer facing) systems in the IT world there is huge pressure on technicians to get things working as quickly as possible - calling in an electrician who might not turn up for a few hours simply isn't an option. Being able to unplug a rack from one supply and plug it into another nearby supply has saved things on my watch at least once.


  - Andy.

This does bring out a point from BS7671, which is the blanket requirement for RCDs for sockets up to 32A. In an installation such as this with supplementary bonding to earth, the RCD has exactly zero use!

But supplementary bonding won't protect against instances of direct contact - e.g. from a damaged flex - where a 30mA RCD will provide some benefit. I've certainly seen flexes trapped in 19" rack doors and pulled around sharp edges of some of the metalwork before now. Certainly they're the situations it's easy to avoid with a bit of care - a policy of properly securing flexes and only allowing access to (authorized) persons with a bit of nous would seem to do - but we can't really assume that without a risk assessment to say that's the case. A lot of IT types, which very technical in some ways, really don't appreciate the hazards of mains electricity.

Same with plug and socket-outlet. They're all just isolators.

Sorry, but I've got to disagree with that. Plugs & sockets mean that IT technicians and change the power supply arrangements safely. Bare in mind that when something goes wrong with live (i.e. customer facing) systems in the IT world there is huge pressure on technicians to get things working as quickly as possible - calling in an electrician who might not turn up for a few hours simply isn't an option. Being able to unplug a rack from one supply and plug it into another nearby supply has saved things on my watch at least once.


  - Andy.