Discuss Can't seem to find the answer, 18th edition tommorow ; ) in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

k is either 115 or 143, depending if its single core cable or multicore. 160 is the temp.

143 is k value for thermosetting, 115 for thermoplastic, therefore answer is 3.67
As it is computerised, you have to be spot on with the answer, an assessor may have accepted 3.6 or 3.7 but I was marked incorrect on a computerised test paper for doing just that, rounding to nearest decimal point when the answer should have been to nearest 2 decimal points.
 
Sorry, 143 is also the value for thermoplastic single core cables.

My copy of the 18th (Table 43.1) only shows 1 figure for copper conductors, final temperature of 160deg C as k=115, for 70 deg C thermoplastic cables depending upon if less than 300sq mm.

Whether single or multicore cables, doesn't seem to have a bearing on the k figure (as far as the 18th and table 43.1 goes).

Either way 143 gives and answer (5.68s) which is obviously incorrect as it wasn't one of the multiple choice answers provided.
Another clue that it is incorrect! table 43.1 is for disconnection times upto 5seconds.
 
Hi Stephen
can you please advise me where to obtain a revision paper for the 18th edition please?
Thanks in advance.
There's an 18th Edition 'exam simulator' here if you want a practice run.

18th Edition Exam Simulator | -----------.co.uk - http://www.-----------.co.uk/18thedition/18th-edition-exam-simulator.php
 
But they are for protective conductors only, not for a 'Live' conductor as per the question.
Yes, thing is, they both relate to fault current.
You would not normally size live conductors according to fault current, you’d size them according to the tables in Appendix 4, for Current Carrying Capacity, which would require a larger CSA.
 
Yes, thing is, they both relate to fault current.
You would not normally size live conductors according to fault current, you’d size them according to the tables in Appendix 4, for Current Carrying Capacity, which would require a larger CSA.

Agree with some of what you say but it isn't relevant to the OP's original question!
 
Not so sure about that! All I think WE'VE done is confuse the OP, what with more than one member on here suggesting k=143 is the correct value to use in his question!
143 would be for single conductors.
115 is for conductors that are part of a cable.
For some reason Table 43.1, doesn’t make such a distinction?
Don’t think anyone has suggested that 143 is the correct value to use?
 
143 would be for single conductors.
115 is for conductors that are part of a cable.
For some reason Table 43.1, doesn’t make such a distinction?
Don’t think anyone has suggested that 143 is the correct value to use?

Changed your tune!
As you rightly said k=143 is used from table 54.2 as a single conductor but only for protective conductors, not a live conductor which was the subject of the question!
 
Changed your tune!
As you rightly said k=143 is used from table 54.2 as a single conductor but only for protective conductors, not a live conductor which was the subject of the question!
Not changed any tune.
Live conductors and CPCs both have to carry fault currents.
There’s no difference to the thermal constraints placed on them just because the insulation colours are different.
 

Reply to Can't seem to find the answer, 18th edition tommorow ; ) in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock