Maths and Java Script any one tried it?

[EFLImpudence]

Whatever, 'safety margins' are just that, and we are theoretically constrained to work with the 'maxima' which are stated in the regs, even if those limits are deliberately conservative'.

I am not advocating exceeding the stated maxima but ...

you seem to be saying that for 2.5mm² the 70° will be reached at 27A and the safety margin is it being able to cope with higher temperatures but ...

could it be that the conductor (2.5) can actually handle more than 27A - say, for example, 35A (I have no idea of the actual figure) - and the 70° would never be reached with compliant installation?

 

[JohnW2]

you seem to be saying that for 2.5mm² the 70° will be reached at 27A and the safety margin is it being able to cope with higher temperatures but ... could it be that the conductor (2.5) can actually handle more than 27A - say, for example, 35A (I have no idea of the actual figure) - and the 70° would never be reached with compliant installation?

No, if you read carefully what I wrote, I said that we cannot tell which (or both) of those is the case - i.e. we don't know 'where' the 'safety margin' has been built in. Well, that's certainly what I was trying to say!

All we 'know' is that 2.5mm² 'clipped direct' can almost certainly carry currents appreciably in excess of 27A without coming to any harm. However, we don't know whether that's because 27A won't raise the conductor temp to 70°C and/or because the temperature does rise to above 70°C (if current >27A), but that temperature does no harm. However, as I said, FWIW, 'Equation 6' seems to imply the latter (because it seems to assume that, in this example, conductor temp will be 70°C with 27A flowing). The reality probably is that it is a 'bit of both' - so I guess the question (which we can't answer) really relates to which of these things (if either) is the 'predominant' one as far as 'safety margin' is concerned.

Kind Regards, John

 

[ericmark]

I was told the 26A figure at an IET lecture I have not seen it written down. I had queried the 106 meter figure for length of cable in a ring because I could not get those figures with my calculations.

I think the limits with meters, parallel paths mean until the volt drop exceeds around 20 volt one would not raise it as an issue.

With switch mode power supplies today there is not so much of a problem with volt drop.

I noticed when I started to use a loop tester I got to recognise when there was a fault I think if one calculated the volt drop the same would apply you would get a feeling when it was not right.

Since Excel no longer works on my phone and Java script does I wanted to re-write in Java script that is now done.

The Schedule of test results format was what I was originally looking at. The idea was on an EICR one could enter figures and quickly check for errors with reports in red when it was detected there was some fault. Original idea was printable version but my Java Script skills don't stretch that far.