Can't seem to find the answer, 18th edition tommorow ; )

[DefyG]

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.

 

[Deleted member 26818]

Sorry, 143 is also the value for thermoplastic single core cables.

 

[stephen fenton]

5.68s.
Looks like they used 115 for k.
Though there’s nothing in the question to tell us whether it’s single core or part of a cable.

There isn't to be fair

 

[DefyG]

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.

 

[Deleted member 26818]

Ah, I think we’ve all been using tables 54.2 through to 54.5.

 

[stephen fenton]

Well I passed it anyway folks and yu know that question never arose

 

[Deleted member 26818]

I just did mine and a very similar question did arise.
How much was your exam?
Mine was £125.

 

[Deleted member 109422]

i am it was a revivision paper lol nice one will study it some more now ; )

Hi Stephen
can you please advise me where to obtain a revision paper for the 18th edition please?
Thanks in advance.

 

[Sintra]

There's one on our resource section 18th edition sample questions - https://www.electriciansforums.co.uk/resources/18th-edition-sample-questions.133/

 

[DefyG]

Ah, I think we’ve all been using tables 54.2 through to 54.5.

But they are for protective conductors only, not for a 'Live' conductor as per the question.

 

[Shoei]

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

 

[Deleted member 26818]

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.

 

[DefyG]

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!

 

[Deleted member 26818]

Agree with some of what you say but it isn't relevant to the OP's original question!

I think we’ve already answered the OP.

 

[Deleted member 109422]

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

Thanks Shoei!

 

[DefyG]

I think we’ve already answered the OP.

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!

 

[Deleted member 26818]

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?

 

[DefyG]

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!

 

[Deleted member 26818]

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.

 

[DefyG]

But in the context of the question posted by the OP your quote

Sorry, 143 is also the value for thermoplastic single core cables.

Is wrong and therefore confusing for the OP and you have almost accepted your error by your statement tonight

115 is for conductors that are part of a cable.