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AS/NZS 3100 - what is ‘standard test finger’

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  1. #1
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    Default AS/NZS 3100 - what is ‘standard test finger’

    An electrical safety inspection of my rental property noted several power outlets and light switch covers with visible screws.

    the report says these are a fault because ‘exposed screws on the switches and power outlets are considered a exposed conductive part under the legislation AS/NZS.3000:2018 and are a safety hazard. The definition is as follows; a conductive part of electrical equipment that (a) can be touched with the standard test finger as specified in AS/NZS 3100, and (b) is not a live part part but can become live if basic insulation fails.’

    Does anyone have access to
    AS/NZS 3100 who could look up the definition of ‘standard test finger’ for me?

    The screws are well below the surface of the plastic units and could only be touched by inserting something long and thin like a screw driver.

  2. #2
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    Obviously the person doing the test never bothered to read the rest where it gives the exceptions and recessed light switch and GPO screws are the exceptions as they can't be touched in normal operation.

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    In my copy of AN/NZS 3000 there is no "definition" of a "Standard Test Finger" indexed under "Standard", "Test" or "Finger".

    However, if you "look-up" "Standard Test Finger" on the WWW you will find many products and illustrations of such an "IEC" specified device.

    Here is one of many

    IEC Jointed and Unjointed Test Finger

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    Old style Clipsal, HPM and RingGrip power points had little plastic caps to cover the fixing screws. The screw holes would have been around 6mmř and the screw heads recessed by ~4mm, and IIRC the caps were to protect "standard test fingers". A small infant may well be able to poke a finger into a 6mmř hole.
    Before you speak, ask yourself: Is it necessary, it is true, does it improve on the silence? - Baba

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    I’ll retrieve the photos - I think some may be closer to the surface and others are quite deep and would be hard to touch.

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    Found these
    4c78e810-1c22-4bc2-8638-5421e92319e7.jpg

  7. #7
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    There were often spare caps on the inside of the power point or light switch to replace ones damaged when the outlet is removed for service. You can see two spare caps on the rear of a gpo in the picture below.

    Attached Thumbnails Attached Thumbnails s-l500.jpg  
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    Such *caps* sre still "Required* under AS/NZS 3000 - where applicable - and are readily available at all the well known suppliers!

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    Quote Originally Posted by FrodoOne View Post
    Such *caps* sre still "Required* under AS/NZS 3000 - where applicable - and are readily available at all the well known suppliers!
    How did you work that out?

    Not how I read the exceptions in 1.4.62

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    Quote Originally Posted by Bros View Post
    How did you work that out?

    Not how I read the exceptions in 1.4.62
    The "Exceptions" relate to "Exposed Conductive Parts" in AS/NZS 3000-2018 1.4.62 (which "can be touched with the standard test finger.")

    As I read these exceptions (without actually quoting them)
    (1) does not apply, since the screws concerned are not within an "enclosure", where a "key" or "tool" is required to remove the cover.
    (2) does not apply, since the screws are not "within" "electrical equipment"
    (3) does not apply, since the screws are not separated from live parts by "double insulation" or "earthed conductive paths".
    (4) does not apply, since the screws could become "live", in the event of "failure of insulation".
    (5) does not apply, since there is no removable/hinged conductive panel fitted to an "enclosure".

    Apart from this, there are Socket-Outlets and Switch Plates which are supplied with "Cover Plates" which cover the fixing screws concerned
    These "Cover-Plates" prevent any such fixing screws being "touched with the standard test finger" in normal operation.
    (e.g. The "Clipsal" 2000 Series.)
    However, such "Cover-Plates" can be removed without the use of a "tool", leaving the mounting screws accessible by "the standard test finger."

    Have you noted that the manufacture of these products is now supplying such devices with "screw caps", so that, if installed, these devices will still comply with 1.4.62, even if the Cover-Plate is temporally or permanently removed.
    This was not done with early supplies of such devices and it may be that the manufacture has "realised" that such protection is "necessary" to comply with 1.
    4.62 - in the event of the "Cover-Plate" being removed, even temporally - for painting, cleaning etc.

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    The testing company got back to me very quickly with this response explaining why the items were not exceptions:

    Upon further inspection, exceptions to the term ‘exposed conductive part’ does not apply to any of the followingConductive parts that are in the form of nameplates, screw heads, covers and similar attachments that cannot become live in the event of failure of insulation of live parts because of the manner in which they are supported and fixed.

    In this case, the recessed screws on the light switches and power outlets are does not meet the criteria for this exemption because they can become live and need to be covered by a face plate. In the past, screws used to have a plastic cover over them and now are behind face plates.’

    I’m getting quotes to make these safe(compliant. Here are
    photos showing some of the the switches/outlets.







    Attached Thumbnails Attached Thumbnails 088bfd20-2300-4b49-8817-33963a946bd6.jpg   4f4e5e05-d6ce-4e1e-9e37-75e2bd23e44e.jpg  

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    Quote Originally Posted by joynz View Post
    The testing company got back to me very quickly with this response explaining why the items were not exceptions:

    Upon further inspection, exceptions to the term ‘exposed conductive part’ does not apply to any of the followingConductive parts that are in the form of nameplates, screw heads, covers and similar attachments that cannot become live in the event of failure of insulation of live parts because of the manner in which they are supported and fixed.

    In this case, the recessed screws on the light switches and power outlets are does not meet the criteria for this exemption because they can become live and need to be covered by a face plate. In the past, screws used to have a plastic cover over them and now are behind face plates.’

    I’m getting quotes to make these safe(compliant. Here are
    photos showing some of the the switches/outlets.

    One could argue that the (short) mounting screws holding the socket outlet shown in the second picture are covered by Exception 3.
    With the plastic "block" used, the screws are installed in a metal insert molded in the plastic and the rear of this mount is not "open", which is why the screws must be short - as shown in the picture below.

    Hence, they are
    "effectively and permanently separated from live parts by
    -double insulation" (The plastic insulation of the "block" and the insulation of the socket-outlet, wires etc.)




    Also, if what looks to be a metal plate shown in the first picture were to be "Earthed", any mounting screws could NOT "become live if the basic insulation fails", since "energisation" of the screw or metal plate would then cause the circuit breaker concerned to 'trip".

    In fact, if that is a metal plate ("Exposed conductive part") and it is not effectively "Earthed", it is a much more significant problem than having "several power outlets and light switch covers with visible screws" !

    So, what was wrong with the inspector in not commenting on that ?
    Attached Thumbnails Attached Thumbnails block-screw.jpg  

  13. #13
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    That’s not a metal plate in the OP photo - it’s painted wood.

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    Quote Originally Posted by joynz View Post
    In this case, the recessed screws on the light switches and power outlets are does not meet the criteria for this exemption because they can become live and need to be covered by a face plate. In the past, screws used to have a plastic cover over them and now are behind face plates.’

    I’m getting quotes to make these safe(compliant. Here are
    photos showing some of the the switches/outlets.
    ....given its just a rental, couldn't you just fill the screw holes with white silicon.
    The screws can still be used at some future point by easily forcing in the screwdriver to the screw head.

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    Quote Originally Posted by Bart1080 View Post
    ....given its just a rental, couldn't you just fill the screw holes with white silicon.
    The screws can still be used at some future point by easily forcing in the screwdriver to the screw head.
    Yes, that seems like an option - or to use caps.

    I’m getting a quote for the installation of a RCBO to the oven sub-circuit and have asked for a quote to ‘make the items safe’. Will be interesting to see if caps, total replacement - or some other option like silicone is suggested. I like the idea of caps.

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    Quote Originally Posted by joynz View Post
    That’s not a metal plate in the OP photo - it’s painted wood.
    Thank you.
    Hence, my second set of comments are not applicable.

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    Quote Originally Posted by Bart1080 View Post
    ....given its just a rental, couldn't you just fill the screw holes with white silicon.
    The screws can still be used at some future point by easily forcing in the screwdriver to the screw head.
    Not a good idea, since a "Standard Test Finger" could also be "forced" into the silicone to touch the screw head.

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    Quote Originally Posted by FrodoOne View Post
    Not a good idea, since a "Standard Test Finger" could also be "forced" into the silicone to touch the screw head.

    How does that work?
    With the manufacturers plugs a screwdriver can simply be forced through them as well, so would that also not pass a "Standard Test Finger"

    Or have I misunderstood your statement ?

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    If this is a rental I would be more concerned about the TPS cable not physically protected and open to damage in an accessible location.
    (Talking about the supplies down to the light switch on timber)
    Personally I would be getting that abortion cleaned up.

  20. #20
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    Quote Originally Posted by droog View Post
    How does that work?
    With the manufacturers plugs a screwdriver can simply be forced through them as well, so would that also not pass a "Standard Test Finger"

    Or have I misunderstood your statement ?
    There are degrees of force !

    (Also, the silicone could be difficult to remove and would not look good in a "home" situation.
    The caps are not that "expensive" - when bought in "quantities" - and are [presumably} the "approved" device.)

    Silicone is fairly soft while a "cap" is quite hard and requires a much large amount of force.
    I know that some "electricians" just remove them in this fashion (and, hopefully, replace them with new ones).

    However, these caps can be removed intact by the careful use of a sharp "craft knife" to lever up the edges, after which they can be replaced intact!

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    Quote Originally Posted by FrodoOne View Post
    There are degrees of force !

    (Also, the silicone could be difficult to remove and would not look good in a "home" situation.
    The caps are not that "expensive" - when bought in "quantities" - and are [presumably} the "approved" device.)

    Silicone is fairly soft while a "cap" is quite hard and requires a much large amount of force.
    I know that some "electricians" just remove them in this fashion (and, hopefully, replace them with new ones).

    However, these caps can be removed intact by the careful use of a sharp "craft knife" to lever up the edges, after which they can be replaced intact!

    You must have much different caps than the ones I come across.

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