I have a Client that will not provide a Risk Assessment to omit an RCD Commando Socket for a Data Cabinet. He wishes to employ a local isolator for the Cabinet, however he is concerned that the PDU Strip that arrived on site from the factory and pre-fitted within the data cabinet would still need an RCD. It is my opinion that the Factory built Data Rack is classed as a piece of equipment and as such does not form part of the Contractor's installation. If the Rack had arrived on site without the PDU strip fitted and it was installed by the Contractor then this would form part of the installation and therefore would require an RCD. Any advice/assistance would be appreciated.
The 'obvious' fear of 3 phases is probably over stated, so long as the neutral is not shared and then accidentally lost.
any one load will see only a single phase supply,and redundant supplies don't merge outputs until they are a ground referred DC.
It takes a certain incompetence to get the phase to phase voltage anywhere that only 230V is expected, and when it happens ADS normally sorts it safely although some kit may be lost.
But this is precisely why I asked the specific question whether you were advocating 30 mA RCD protection for couplers as well!
In fact, I agree it's a difficult situation to grasp, but at the end of the day the Reg exists for "couplers" separate to "socket-outlets", and I can't see the difference between "appliance outlet" and "free outlet" in the context of a cable coupler.
So, the question - should couplers be included in 411.3.3 ? I sort of think you're saying they should be.
From the point of view that if an ordinary person has a lead with a plug on the end of it (be it BS 1363, BS EN 60309, BS EN 60320 or anything else), they're just going to plug it into anything that fits - they're not going to be bothered if BS 7671 considers it a socket-outlet or a connector. All else being equal (i.e. unless a risk assessment says otherwise) the risks will be similar - so, yes, it would seem logical to me to treat them similarly.
It would seem more that a little absurd that where a 32A BS EN 60309 wall mounted socket needs 30mA RCD protection, a wall mounted isolator with a stuffing gland supplying 6" of flex with a 32A BS EN 60309 female coupler on the end of it, in the same situation, would be exempted. (I note that the title of BS EN 60309 is "Plugs, socket-outlets and couplers..." so that's no help.)
I do take your point however, that compliance with BS 7671 isn't always the same thing as complying with my idea of logical. But I still think we need to deal with BS 7671's definitions when reading BS 7671 regulations - rather than definitions (or titles) from other standards - and to me the chassis mounted C13s look to better fit to BS 7671's definition of a socket outlet than to its definition of a connector. Whether it's a socket outlet of itself, or other equipment incorporating a socket outlet (which may or may not have to comply with table 55.1 etc.), is to me a side-issue.
Maybe we're just going to have to agree to disagree on this one...
IT cabinets are 3 Phase and I dread the thought of an IT Technician interconnecting the power to dual fed Servers for obvious reasons.
I totally agree with Mike and Graham - there's absolutely no problem mixing phases on modern equipment (we did it frequently with dual-PSU servers - typically one from mains and the other from a UPS so there might have been more than 400V between them!) - there's not even any need for a 'Danger 415V' sticker any more - since Uo is still only 230V.
It would seem more that a little absurd that where a 32A BS EN 60309 wall mounted socket needs 30mA RCD protection, a wall mounted isolator with a stuffing gland supplying 6" of flex with a 32A BS EN 60309 female coupler on the end of it, in the same situation, would be exempted. (I note that the title of BS EN 60309 is "Plugs, socket-outlets and couplers..." so that's no help.)
Precisely the same thing could be said about lighting couplers, and to an extent installation couplers, but see Note 3 to Reg 411.3.3 ... and again 553.2.1 (assume not domestic/household premises so 411.3.4 doesn't apply).
I think however, that precisely because all of these different uses of effectively what is a "socket-outlet" exists, and because we have a requirement for "general user-accessible socket-outlets" to have some basic safety standards for the electrical installation (e.g. shuttered socket-outlets) is why it's difficult to put together a coherent set of requirements.
One last thought on the "coupler" issue.
There's a requirement for household and similar use socket-outlets to be shuttered. Many IEC 60320 outlets are not shuttered. You've said "What's the difference"?
Perhaps BS 7671 should make the statement that if a coupler is accessible in a household or similar use, then it should be shuttered as well as RCD protected?
But to be brutally honest, what's the point if we've all got appliances with supply cables having unshuttered free IEC 60320 outlets on them?
