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

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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..

mapj1 · Accepted Answer

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.

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