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Internal inspection of sockets and switches.

hertzal123
Some years ago on doing some remedials on a report,I noticed the inspector had put "internal inspection of selected

sockets and switches".Wondered if this is acceptable instead of giving a percentage of the inspections?

                                                                                                            Regards,

                                                                                                                     Hz
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    It appears that item 5.17 on the Condition Report Inspection Schedule requires only an indication of the “extent” of sampling but if you look on page 479 under termination of cables at enclosures it suggests identifying numbers and locations.

    I think the key point should be to minimise bureaucracy and focus on the inspection activity. Of course that will rely on the integrity of the inspector!
  • 0
    Selecting some sockets is not the same as sampling them.


    Any sample should either be random (I doubt that happens very often) or state how they were selected.


    I think that we all know that the same selection should not be inspected time after time.?
  • 0
    Chris Pearson:

    Selecting some sockets is not the same as sampling them.


    Any sample should either be random (I doubt that happens very often) or state how they were selected.


    I think that we all know that the same selection should not be inspected time after time.?


    We never normally select the sockets behind large heavy appliances like washing machines or tall fridge freezers.


    Z.


  • 0
    thanks for the replies,

                             Hz
  • 0
    When my daughter bought a new (old) house I did an inspection of the electrics. All was well and I remember removing one particular socket (brushed chrome) and  the connections were OK and tight so I refitted it.


    A couple of months later she commented that if she used this particular socket it tripped the RCD. I found a screw had fallen out (it was in the back box) and the innards of the socket were loose as a result, which cause a short when a socket was inserted. It was a very cheap socket brand. I suspect the MCB also tripped but she was a bit vague about it.


    How far can one go with an EICR.
  • 0
    kfh:

    When my daughter bought a new (old) house I did an inspection of the electrics. All was well and I remember removing one particular socket (brushed chrome) and  the connections were OK and tight so I refitted it.


    A couple of months later she commented that if she used this particular socket it tripped the RCD. I found a screw had fallen out (it was in the back box) and the innards of the socket were loose as a result, which cause a short when a socket was inserted. It was a very cheap socket brand. I suspect the MCB also tripped but she was a bit vague about it.


    How far can one go with an EICR.


    As far as is reasonably practicable. At least in most cases of faults the protective devices do their job well.


    Z.


  • 0
    kfh:

    When my daughter bought a new (old) house I did an inspection of the electrics. All was well and I remember removing one particular socket (brushed chrome) and  the connections were OK and tight so I refitted it.


    That's the problem with disassembling things in order to inspect them. So having done your walk around, do you inspect the innards of the dodgy looking sockets, or do you leave them alone for fear of making things worse? ?


  • 0
    Chris Pearson:

    Selecting some sockets is not the same as sampling them.


    Any sample should either be random (I doubt that happens very often) or state how they were selected.


    I think that we all know that the same selection should not be inspected time after time.?


    Also, sampling where the sample population is less than 100 is not valid.


  • 0
    Mr Kenyon,

    are you having a ? ?


    Sorry I could not find a pic of a Giraffe so I put an Octopus instead
  • 0
    I think Graham's comment is not intended to be take literally (well I hope not). Clearly as the sample size is reduced, the risk of picking up an unrepresentative number of good or bad examples rises, and the indeterminacy  of the sample result versus what you would have seen with 100% sampling increases. (the so called 'law of small numbers')

    This is not to say that you cannot do a sampled test on a small number of items, just that you need to be aware of the perils of doing so.

    Mathematics only really comes to the rescue properly in the case of a supposedly identical set of samples, telling you your confidence/uncertainty  in relation to sampled fraction say the output of a production line.

     ( the canonical example has to be Bruceton Analysis often applied where sampling is destructive so you cannot afford too much of it- imagine testing the yield of a hand grenade factory, or closer to home the correct blowing of fuses. Neyer d-optimal test  may be better for tests where the output is a number rather than a simple yes/no such as determining breakdown voltages with a given confidence for as few tests as possible.


    This is all very pretty but really so much hot air for an EICR/PIR situation.


    The problem is in applying the formal statistics to inspecting something like the set of all 13A  sockets on the ring is that they are not really a set of identical objects.  The one most used for vacuum cleaning is far more likely to be externally damaged, the ones in the kitchen are more likely to have been overloaded or wet, etc.


    And even if that was not the case, we are not after a yield fraction in the stats sense, we want to find the failures, so we should look first at those locations most likely to be problematic- which I suspect experienced folk can do, because in practice once you find one serious problem, the 'how many more should I look at ?' answer changes (upwards), or at least it should.

    After all, to condemn the circuit, you only need one killer fault.

    M.


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