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

[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.

 

[Deleted member 26818]

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


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

What error?

 

[DefyG]

Suggesting k value should be 143 then you have corrected it tonight to 115

 

[Deleted member 26818]

I have at no time suggested the value of k should be 143.
What I have said, is the value of k for single core cables is 143 and that the tables 54.2 through to 54.5 can be used for both live conductors and protective conductors.

We had already established that the value for k to be used in the question was 115, before you posted.

 

[DefyG]

I'm sorry, I believe you are wrong tables 54.2 - 54.5 clearly state - Values of k for 'protective conductor' in the relevant heading for whatever form it may take, conduit, trunking, armour etc.
I do not believe the tables should be used for 'live' conductors, which is why table 43.1 is in the book.
I'm surprised no one else has waded in with their two penny worth!
I think we can agree to disagree on this one!

 

[tudore]

yeah got that but they gave us four outcomes which was 0.4s/1.92s/3.67s/5s i didn't stipulate this in the beginning but 5s I'm guessing they have just rounded it off.

Be careful with table 43.1: I'm pretty certain the value for k is 115, and answer is 3.67.