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Interlocked sockets

Hi all.


Recently had a contractor carry out a periodic inspection on our site (warehousing and workshops) and they have specified that all the 16A and 32A (1ph & 3ph) sockets need to be interlocked.


Is this true, or are they just finding £5k of additional work to carry out?


I can only find reference to caravan sites (Sec. 708) requiring interlocked sockets. 


Any other sections that reference this requirement on industrial and commercial installations?


Thanks in advance,

Neil

  • Is the contractor thinking of 557.6.6?

    Alasdair
  • Hi Alasdair.


    I think this is referring to specifically to auxiliary circuits. Might be an element to what you are suggesting but will go back to the contractor to clarify which regulations they think apply.


    Thanks for the response.


    Neil
  • Neil,

    I did realise that the paragraph I mentioned referred to auxiliary circuits, but I was struggling as much as you are to find any basis for the contractor specifying interlocking. However I have given it a bit more thought and think it may be 553.1.1, along with table 55.1.  This does not mention interlocking so it is a bit of a jump, but industrial plugs and sockets to BS EN 60309 can be produced  as "interlocked" and "non-interlocked" options (BS EN 60309-2 Clause 12 applies) so it may be this that the contractor is thinking of.

    Anyway, I will be interested to learn what the contractor says.

    Alasdair
  • I can think of no reason why these should be interlocked from the Regs. This sounds like the inspector needs some proper training! The interlocked requirement only applies to certain special locations.
  • Hi all.


    Thanks for the input.


    Have gone back to the contractor and awaiting clarification. This is one of a number of questions raised on the results sheet.


    I also contacted Mennekes technical, who had not heard of this, other than EV charging and Caravan parks. If the people who make the sockets haven't heard this, then it must be highly questionable, otherwise they would be making a fortune replacing the hundreds of thousands of sockets out there...wink


    Thanks again,

    Neil
  • My guess is that your inspector is thinking about the plug/socket being used for functional switching (but I suspect he's got the detail wrong). There used to be a regulation (e.g. 637-05-04 in the 16th) that a plug & socket not exceeding 16A could be used for functional switching - so it was normal to see switches on 32A and larger sockets - presumably interlocked if you couldn't necessarily trust all your users to reliably switch off before unplugging. I suspect your contractor has that value in mind (but has muddled ≤ 16A with <16A). However from the 17th onwards the limit moved up to 32A from 16A (table 537.4) - so now no switches (interlocked or otherwise) needed on 16A or 32A sockets (but still might be for larger units).

       - Andy.
  • Thanks for the additional information, Andrew. 


    This makes sense and highlighting Table 537.4 definitively highlights the situation with regard to isolation and functional switching.


    None of these outlets are over 32A, so fine for Isolation and Functional Switching. 


    Still can't find any references to interlocks other than Section 708 and electric vehicle charging.


    Thanks again,

    Neil