Mentor or discussion forum on IET 5th EDITION code of practice

WHERE do I get LEARNING discussion topics and feedback as I would in a classroom format or from a college mentor on many QUESTIONS I have regarding 5th EDITION IET Code of Practice?? 

For example on Page 80 Table 10.6..  1.5 mm cable has a maximum current carrying capacity of 13 Amps.... YET online I am finding PAT engineers testing Industrial extension leads 1.5 mm having 16 Amps run through them and in BLACK cable with BLACK sodding 60309 connectors... EXTREMELY baffelling and not with an axe to grind and as a none electrician am taking the exam soon THINGS are NOT matching up to spec...I need clarification.. I need answers to many seemingly oddball stuff..

Another quick on:   Page 98-99  5th Edition IET..  If you want peeps to get confused this is it:  ES1 is equivalent to Class III ok... then ELV and SELV (no PELV and no FELV??) are WHAT.. class II? 

An exam Q will TRY an TRIP me up over Low Voltage and Extra Low Volts ok.. seemingly obvious YET online sources declare 0-1000 volts AC and 0-1500 volts DC as Low Volts yet another no no no its 120-1500 DC and 50-1000 AC

IF i take that second reference at FACE value on page 99 in the IET we see a table declaring ES2 at 120 volts DC 50 AC  what is that doiing sat right in the MIDDLE of that table??  and what is ES2?  its not clear and I am in mind

to class ES2 as CLASS II...... furthermore in SELV we see a sodding CP being available as basic protection in some cases?????????  Getting really strapped over this guys..

  • Well, speaking personally, some of these I can advise,  on but note I do not teach this nor do I have any input into the docs themselves so do not shoot the messenger please.
    what books are you looking at ?

    Lets hit a few,

    1) Cable ratings are not hard and fast, as it depends how the cable will be used. The rating is really the current at which the copper core gets hot enough that it may in the long term damage the plastic of the insulation. A cable coiled or in a place that is already warm like a boiler room will not be able to safely carry as much current as the same cable spread out or just in a cooler place.  You will see different ratings for the same cable published, and always look for the test conditions (BS7671 seems to liek 30 degrees ambient but ungrouped as the base case, then de-rating with hotter settings, or up-rating when it is cooler, and of course reducing the rating when grouped.  Other national standards assume similar but not identical things, and as far as I can tell the IET does not always assume the same thing in all its publications either ....)
    In the UK it is almost never 30C so the BS7671 ratings can often be pushed a bit in practice.

    2) I presume by 60309 connectors you mean the 16A ones that can under certain situations be pushed ot 20A. Nothing stopping you fitting a thinner flex if you know the load is never going to be the full 16A (is it just used for lighting perhaps) or if it is fully loaded but the load is only on for a few mins at a time so the cable has no time to heat up  - as an example your kettle at home may well be 3000watts (12 amps say) on 0.75mm2 flex - but its fine because by the time the cable is getting hot the kettle has pinged off.

    3) ES1, ES2 ES3 MS1 MS2 MS3  do  not map to the ADS types 0, 0A, 1,2 etc

    The ES series are energy limits are more useful for deciding what precautions to take when deciding how skilled folk need to be to be operating  kit wit with the lid off, MS are mechanical hazard ratings for things that are heavy or have other risks,  like entrapment or  rotating parts inside.


    The ADS types are just that  types  of ADS, of which only class 1 and class 2 are common in the UK, but sometimes you will see things that are a mixture so the rack is class 1 but the kit in it is class 2 for example.
    Class 3 is for things that run on ELV,

    Note the UK uses the IEC voltage  levels.Avoid those of other countries, yes the web  is a confusing place.

    EC voltage range     AC RMS  (V)          DC voltage (V)        Defining risk
    High voltage                  > 1 000               > 1 500                 Electrical arcing
    Low voltage            50 to 1 000               120 to 1 500         Electrical shock
    Extra-low voltage     < 50                      < 120                     Low risk
    Though folk often forget the risk of  fire from higher  currents at ELV.

    Mike.

  • Might be useful if you could say which code of practice you're referring to (I believe the IET publish quite a few, on different electrical subjects), but chances are you're in the right place for a discussion (arguments are next door ... to misquote Monty Python).

    To clarify the clarification as it were, BS 7671 defines extra low voltage as not exceeding 50V AC or 120V ripple free DC, and low voltage as exceeding extra low voltage but no exceeding 1000V AC or 1500V DC between conductors, or 600V AC or 900V DC between a conductor an Earth. Above that is high voltage (p 44 of BS 7671). The definition often does get shortened for brevity, rather than clarity, and some sectors (e.g. transmission) tend to think of their bit as High Voltage and everything else as Low Voltage.

    I think the ES classifications have been adopted by the standards for some types of electrical equipment (e.g. AV & communication equipment) for shock protection in general. They do the same sort of job as Class I, Class II class III etc, but take a different approach (partly by limiting the energy, rather than just the voltage, available for a shock), so aren't directly equivalent. It all gets a bit messy when all sorts of wires come out of such equipment and back into the building and so other standard (e.g. BS 7671 apply as well). Others here may know much more about the details.

        - Andy.

  • Hi I have had discussions with PAT involved persons over the years --Beware - many do not know the regs or count on a client not knowing the regs to charge for unneeded tests. IE--- PAT is Portable Appliance. I had one idiot try and tell me that a walk in cooler is a portable appliance. Then how do you check the fuse in an unfused 15 amp plugtop. 

    Just read the regs carefully- and the answers are there. Some tests are only required on a three year basis, a table lamp say,

    Others such as an Iron or a Hoover more frequently. But the user should be looking at the leads each time the appliance is used. Due to the nature of the appliance operation.

    I have other kit that takes two men to lift and exceed the weight limit of a portable appliance.

    So don't worry about others RTFM for your self.

  • For example on Page 80 Table 10.6..  1.5 mm cable has a maximum current carrying capacity of 13 Amps.... YET online I am finding PAT engineers testing Industrial extension leads 1.5 mm having 16 Amps run through them and in BLACK cable with BLACK sodding 60309 connectors... EXTREMELY baffelling and not with an axe to grind and as a none electrician am taking the exam soon THINGS are NOT matching up to spec...I need clarification.. I need answers to many seemingly oddball stuff..

    The table of Page 80 only applies where there's a BS 1363 plug (see table title and the title of Section 10.14 in which the table sits). Whilst  1.5 mm2 flexible cable can be rated for up to 16 A, this is NOT the case with a BS 1363 plug, where the rating is limited to 13 A.

    Another quick on:   Page 98-99  5th Edition IET..  If you want peeps to get confused this is it:  ES1 is equivalent to Class III ok... then ELV and SELV (no PELV and no FELV??) are WHAT.. class II? 

    A glib answer is 'no longer used in some standards'

    'ELV' is just a term that defines the level of voltage, 'extra-low voltage'. This comes in a number of variations as to how the voltage is derived, so:

    • SELV is 'separated extra-low voltage' and has particular protective measures to prevent electric shock under single fault conditions.
    • PELV is like SELV, but is additionally earthed (this may be for a number of reasons selected by a manufacturer or electrical installation designer)
    • FELV may have higher voltages present, so needs ptorection similar to mains (low voltage).

    Installation standards, and some product standards, still use 'SELV' and 'PELV'. However, to complicate matters, some standards like BS EN 62368-1 no longer align with the usage. It makes things far more complicated for those learning about product safety, and tutors teaching it. The changes to classification and better descriptions are in Appendix 3 of the Code of Practice (starts on page 97).

    IF i take that second reference at FACE value on page 99 in the IET we see a table declaring ES2 at 120 volts DC 50 AC  what is that doiing sat right in the MIDDLE of that table??  and what is ES2?  its not clear and I am in mind

    ES2 is equivalent to either FELV or mains (low voltage, LV) depending on the nominal (normal) voltage involved in the system (and where it is used according to BS 7671). It is there to compare the fact that ES2 is NOT equivalent to either SELV or PELV., because of the possible touch voltage or touch current in single fault conditions - it could only be considered FELV or LV.

    to class ES2 as CLASS II...... furthermore in SELV we see a sodding CP being available as basic protection in some cases?????????  Getting really strapped over this guys..

    No, it may not be,

  • I have had discussions with PAT involved persons over the years --Beware - many do not know the regs or count on a client not knowing the regs to charge for unneeded tests. IE--- PAT is Portable Appliance.

    A lot of people these days try to avoid the terms PAT or portable appliance these days - even the IET's code of practice is entitled "In-service Inspection and Testing of Electrical Equipment". From an H&S point of view the duty holder needs to make sure that their entire system is safe, and as wiring regs inspections don't cover appliances (whether fixed or portable), it's often useful have an approach that covers 'everything else'.

       - Andy.