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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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    Hang on, that's picking at a single thing from a three-part reasoning.



    Apologies - not having access to BS EN 60320 I can't see the context of its definitions, so I'm having difficulty commenting on that bit. While I can see that the usual female IEC connector on the load end of a flex would certainly be a coupler (or "connector" in BS 7671 definition terms), I still can't see how the panel mount version (connected to "fixed" wiring and intended to accept a C14 plug on the supply end of the flex) would fit the same BS 7671 definitions. Looking at it the the way around, trailing 13A sockets come under BS 1363 - the standard for socket outlets, but surely in BS 7671 terms they're couplers/connectors, rather than socket outlets, when connected on the end of a flex rather than fixed wiring.


    I do see your point about BS EN 60320 items not being listed as being acceptable socket types - but again that of itself doesn't say to me it's not a socket. If I stuck a schuko socket on a wall, I think the usual conclusion would be that it was a departure from BS 7671 (which may or may not be justifiable under 133) rather than it needed to be given the name of a different kind of accessory. If push came to shove I might try and squeeze the use of 60320 "outlets" in under the last bit of 553.1.5 (iii) - 'necessary to distinguish the function of the circuit' (as it's function is to supply equipment that's supplied with IEC-IEC leads).


    So far we seem to be saying that, in the picture of the PDU above, that the right hand four "outlets" are sockets as far as BS 7671 is concerned, and so require 30mA RCD protection (unless a risk assessment concludes otherwise), but the eight "outlets" on the left, are deemed not to be socket outlets, so have no such requirements - even though they're likely to be used in exactly the same way. That's a conclusion I'm not entirely comfortable with.


    It also get really complicated with what are probably some common arrangements...


    13A Socket -> Plug -> Flex -> Appliance - OK (30mA RCD protection required at or before socket)

    FCU -> Flex -> Appliance (might be fixed or hand-held) (no RCD requirement)

    FCU -> Flex -> BS 1363 outlet (as in the pendant socket mentioned before, or a autorewind reel with a trailing socket on the end of the flex) - apparently a connector rather than a socket, so no RCD requirement?

    FCU -> Flex -> BS EN 60320 connector - similarly, no RCD requirement?

    FCU -> BS EN 60320 panel outlet (directly hard-wired, no flex) - not permitted?


    (and I suppose ditto without the FCU when supplied from a 20A or less circuit)


    It's all getting murkier and murkier....


      - Andy.
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    AJJewsbury:




    They are defined as "couplers" ....  in Reg 553.2.1



    Saying that couplers must comply with BS EN 60320 logically isn't the same as saying all things complying with BS EN 60320 must be couplers - that would be like saying since sockets must comply with BS 1363 then all things complying with BS 1363 must be called sockets - and thus you couldn't have a BS 1363 plug.  (Or the classic example, since tables have four legs, all four legged things must be tables).

    Hang on, that's picking at a single thing from a three-part reasoning. Please don't take it out of context. 553.2.1 PLUS the fact that BS EN 60320 is "couplers" and the "outlets" are couplers as they comply with that standard.


    Having said that, you've not responded to the last point - you can't select them as socket-outlets, as that doesn't comply with BS 7671.


    On a wider note, I'm getting less and less happy with the definition of a socket needing to be attached(?) to fixed wiring. There's no definition of fixed wiring (I could see that it could either be wiring that's not free to move, or equally, wiring that can't be readily unplugged from the supply and relocated). If following the example of 'fixed equipment' the former might be expected, but is there really a significant difference between a wall mounted socket and one of these? https://olsondirect.co.uk/4-way-13a-switched-socket-suspended-service-unit.html


       - Andy.

     




    No, and you're quite right.


    When the BS EN 60320 outlets are manufactured into a product and the whole product meets BS 5733, that product may be suitable for connection to the fixed wiring (as in the case of the BS 1363 version you point to).


    You can install an accessory to BS 5733 and connect it direct to fixed wiring, but if it has BS EN 60320 appliance outlet couplers, it will still have appliance couplers (rather than socket-outlets).

  • 0

    They are defined as "couplers" ....  in Reg 553.2.1



    Saying that couplers must comply with BS EN 60320 logically isn't the same as saying all things complying with BS EN 60320 must be couplers - that would be like saying since sockets must comply with BS 1363 then all things complying with BS 1363 must be called sockets - and thus you couldn't have a BS 1363 plug.  (Or the classic example, since tables have four legs, all four legged things must be tables).


    On a wider note, I'm getting less and less happy with the definition of a socket needing to be attached(?) to fixed wiring. There's no definition of fixed wiring (I could see that it could either be wiring that's not free to move, or equally, wiring that can't be readily unplugged from the supply and relocated). If following the example of 'fixed equipment' the former might be expected, but is there really a significant difference between a wall mounted socket and one of these? https://olsondirect.co.uk/4-way-13a-switched-socket-suspended-service-unit.html


       - Andy.
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    I'm not sure that the definition of "socket-outlet" in BS 7671 fully covers couplers, particularly as:
    • They are defined as "couplers" in BS EN 60320, and again in Reg 553.2.1.

    • BS EN 60320 appliance-outlets are not suitable for direct connection to the fixed wiring, they are part of equipment. Equipment should be selected in accordance with BS 7671 (i.e. meets relevant standards, suitable rating etc.)

    • BS EN 60320 is not listed in Table 55.1, as required by 553.1.3 unless 553.1.5 applies, and the use you are alluding to for data cabinets doesn't really come under any of the exceptions listed in 553.1.5 - so if you want to specify them, they cannot be "socket-outlets".

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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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    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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    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.

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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?

  • 0

    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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    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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