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RCD Protection at Data Cabinets

Bob Cowie
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.
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    davezawadi:


    There is a serious problem with the standards making process, and that is that interactions between various ones from differing sources lead to foolish and unnecessary outcomes. The most obvious one is electric cars (chargers) not being class 2 because someone didn't see that they could not safely be earthed in the external environment, which we all know and have a lot of regulations to reduce risks to presumably acceptable levels. However street furniture using PME is considered entirely satisfactory and does not cause a significant number of accidents. We need to be consistent on the basis of real risk only, not on "what if" scenarios.




    EV charging equipment and EVs are made for the global market, and are not limited to the UK. It seems that we in the UK are less happy with the problems that PME might bring ... However, is all this mis-placed? They are having a rough time with PME-related serious occurrences in Australia, not that I'm trying to draw direct parallels as Australia don't quite do things the way we do either.

    But let's be very clear that legislation is the driver here for considering PME risks in the UK, NOT standards.  It's the ESQCR (and its predecessors) that highlight the risk of PME in relevant circumstances, so that can't be ignored. There's not much difference between a caravan and an EV on charge, to be quite blunt; that is, if you ignore the fact that the caravan might have metal legs from the earthed chassis in contact with the ground, but an EV on charge won't !


    The other difference between general street furniture and EV charging equipment, in the main, is that of power rating. This is made quite plain in ENA ER G12/4.

     

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    Gentlemen, I think we have drifted from my initial query. My question was about the internal power strip (generally 13amp) which arrives pre-fitted within the Data Rack. Is this classed as Equipment or is it part of the fixed wiring? The Client through his advisers consider it to be part of the fixed wiring and therefore should have RCD protection as they are unwilling to complete a risk assessment. Their initial thought was to fit an isolator above the rack negating the need for RCD protection and negating the need for them to produce a risk assessment, however they have now been advised that the power strip inside the cabinet requires an RCD or Risk assessment. Feedback from other bodies like Select advise that the power strip is not part of the fixed wiring and it does not come under the EICR therefore an RCD is not needed if you use an isolator rather than an external Commando socket, however if the Contractor fits the power strip after delivery of the rack it becomes part of the fixed wiring. I would appreciate comments on this point.
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    Bob C:

    Gentlemen, I think we have drifted from my initial query. My question was about the internal power strip (generally 13amp) which arrives pre-fitted within the Data Rack. Is this classed as Equipment or is it part of the fixed wiring? The Client through his advisers consider it to be part of the fixed wiring and therefore should have RCD protection as they are unwilling to complete a risk assessment. Their initial thought was to fit an isolator above the rack negating the need for RCD protection and negating the need for them to produce a risk assessment, however they have now been advised that the power strip inside the cabinet requires an RCD or Risk assessment. Feedback from other bodies like Select advise that the power strip is not part of the fixed wiring and it does not come under the EICR therefore an RCD is not needed if you use an isolator rather than an external Commando socket, however if the Contractor fits the power strip after delivery of the rack it becomes part of the fixed wiring. I would appreciate comments on this point.




    To comply with BS EN 50310 fully, the power strip should have a supplementary bonding stud for connection to the rack earthing system for impedance control. This then effectively becomes part of the fixed wiring installation, because it has permanent equipotential bonding from the PE connection in the strip, to the rack earth bar. BS EN 50310 also contains a requirement to conduct impedance tests, so even if delivered "part assembled", still think there's some form of "fixed wiring tests".


    Even if the power strip is outside an EICR, BS 7671 can still be used to select and erect it, therefore I'm not 100 % convinced by that argument. I think this is the case even if the product comes fully or part assembled - it still contains 13 A socket-outlets, therefore the RCD issue of 411.3.3 should be addressed either by installation design (fitting the RCD in the fixed wiring installation), or by selection (i.e. rack has internal RCD protection to meet BS 7671 requirements).


    To comply with BS 7671, the 13 A socket-outlets in the rack require RCD protection, unless there is a risk assessment in place.


    The only other alternative to RCD or risk assessment is to use interconnection couplers (e.g. IEC 60320 J or F) on the power strips instead of BS 1363 socket-outlets. BS 7671 does not require cable couplers and interconnection couplers to be RCD protected, only socket-outlets.

     

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    I've been thinking about this from a different direction, but I'm probably arriving at a similar conclusion to Graham (for once!).


    I've been thinking, not from a BS 7671 and equipment standards point of view, but from a Health & Safety at Work Act & Electricity at Work Regulations direction. The legislation doesn't distinguish between fixed wiring and other equipment, but concentrates on the overall level of safety. So say we had a rather uncontrolled environment. Rack placed alongside the system manager's desk in an open plan working area. IT guys aren't particularly knowledgable about mains electricity but know enough to get things to work. Not adverse to running a lead out from the rack to the desk if they need an extra socket for a new bit of equipment. Cleaner plugs their vacuum into whatever spare socket they can find. Likewise the mobile car valeting guy. Equipment from home sneaks in occasionally. Certainly not all IT offices are like that - but some are (I've been in them).  So we're now at a position where the "norm" is that ordinary sockets for general use are expected to have 30mA RCD protection - so what what your position be if someone used one of the non-RCD sockets supplied from the rack supply for something dodgy and came a cropper as a result?


    Hopefully at this point you're saying something like 'but my environment isn't like that - the rack will be in a locked machine room, or there's no chance of equipment outdoors being plugged into it, or the IT guys have been trained in some basic electrical safety - can't I take those factors into account' - to which I'd say yes of course - but the means the regs provide for doing that (paperwork wise) is via a risk assessment.


       - Andy.
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    Andy,


    Yes, this is another way of looking at it.


    Reg 411.3.3 is pretty much the same across CENELEC countries - it's in the HD. Basically, if a socket-outlet rated ≤ 32 A is available for general use, it should have RCD protection.


    In the UK, the consensus seems to be that general-purpose socket-outlets (BS 1363-2 and BS EN 60309-2) are exactly that ... general purpose, unless you have them locked away somewhere that's only accessible to suitably competent persons, for example ... hence the risk assessment requirement.
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    In the UK, the consensus seems to be that general-purpose socket-outlets (BS 1363-2 and BS EN 60309-2) are exactly that ... general purpose, unless you have them locked away somewhere that's only accessible to suitably competent persons, for example ... hence the risk assessment requirement.



    Same thinking for 60320 sockets? (C13 and C19s?) - pretty common in rack PDUs.

      - Andy.
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    AJJewsbury:




    In the UK, the consensus seems to be that general-purpose socket-outlets (BS 1363-2 and BS EN 60309-2) are exactly that ... general purpose, unless you have them locked away somewhere that's only accessible to suitably competent persons, for example ... hence the risk assessment requirement.



    Same thinking for 60320 sockets? (C13 and C19s?) - pretty common in rack PDUs.

      - Andy.

     




    They are not socket-outlets no matter how common.


    Are you advocating that RCDs are required for couplers now, as well as socket-outlets, and perhaps that the requirement should also be extended to connection units and connecting points too?

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    They are not socket-outlets no matter how common.


    Are you advocating that RCDs are required for couplers now, as well as socket-outlets, and perhaps that the requirement should also be extended to connection units and connecting points too?



    No, not the couplers (e.g. on the end of a flex) - I mean the "chassis mount" outlets - often incorporated into rack mounted power distribution units (PDUs) in just the same way that BS 1363 outlets are. One example:

    4f6f06705975cf05bd91510ff35187dc-huge-42-6082_01.jpg


      - Andy.

  • 0

    AJJewsbury:


    No, not the couplers (e.g. on the end of a flex) - I mean the "chassis mount" outlets - often incorporated into rack mounted power distribution units (PDUs) in just the same way that BS 1363 outlets are. One example:

    4f6f06705975cf05bd91510ff35187dc-huge-42-6082_01.jpg


      - Andy.

     

     




    Andy, the BS EN 60320 outlets are not socket-outlets but are known as "interconnection couplers"


    Basically, there are the following:


    • Cable couplers (e.g. for the 6/10 A version, Type C13 "free outlet" connector and its corresponding appliance inlet coupler Type C14; and

    • Interconnection couplers (e.g. for the 6/10 A version, Type E "free plug" and its corresponding appliance outlet coupler Type F).

    The whole standard BS EN 60230 is entitled "appliance couplers".


    Hence my question, should we extend RCD protection to these also?

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    Continuing to play Devil's advocate... I'll argue that when reading 411.3.3 it's BS 7671's definition of a socket-outlet that counts (rather than what another standard chooses to call them). If we've concluded that the 13A outlets in the above picture are socket-outlets, I can't see anything in BS 7671's definitions that would allow us to treat the C13s any differently. They're both seem to fit the definition of "A device, provided with female contacts, which is intended to be installed with the fixed wiring, and intended to receive a plug. ..." equally. The chassis mount outlets don't seem to fit BS 7671's definition of a Cable Coupler or a Connector at all.


    Even from a practical point of view of how they're likely to be used - there's nothing about them that really prevent ordinary appliances (or extension leads) being supplied by them - C14 to BS 1363 adaptors are readily available and are in practice often to be found in the sort of environment that houses IT equipment in 19" racks (e.g. https://www.apc.com/shop/uk/en/products/Power-Cord-C14-to-BS1363-UK-0-6m/P-AP9881 - if usually sourced from somewhere with more sensible prices!)


       - Andy.

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