Aluminium T&E ccc?

I appreciate that this is not actually answering the question, but are you certain that the conductors are aluminium ?

Tinned copper is is often mistaken for aluminium.

No, but if you look at 543 you will see that the value of k of a copper conductor is about 2/3 that of aluminium, so I think that you could use the tables for a copper conductor of 2/3 the value of the CSA of the aluminium one. You will not go far wrong.


Bear in mind that a 35 mm² aluminium service cable goes with 25 mm² copper tails. 35 x 2/3 = 23 1/3 so not far out.

No, but if you look at 543 you will see that the value of k of a copper conductor is about 2/3 that of aluminium, so I think that you could use the tables for a copper conductor of 2/3 the value of the CSA of the aluminium one.

I'd be wary of implying CCC from k - k is calculated from a number of factors - while conductor resistance will be one factor, so too are things like the thermal capacity of the metal (how much its temperature rises per Joule of heat generated) which can skew things a bit. It's more obvious comparing copper with steel - steel's k value is about 1/3rd that of copper - but it's conductance is only about 1/9th.


   - Andy.

If this is a socket ring circuit in a house does the circuit design need reevaluating after fifty years of service, surely if there’s a problem with voltage drop someone would have done something about it by now?

The original ratings would have been in the 1966 version of the12th edition. Sadly I do not have a copy, but some on here may do and could perhaps scan or photograph the right page.

By the early 1970s, in the all-metric version of the 14th, the regs been purged of the smaller sizes of alu cable. and has nothing less than 10mm2.

Copper flashed aluminium solved some of the corrosion issues of bare ally, but it was still brittle to work with, and by the early 1970s was being phased out again.

Mike.

Aluminium Conductors.


Approx. overall diameter of cable. Inches.         Approx. resistance in Ohms. per

                                                                                          1,000 yards.


0.18                                                                             2.0


0.25                                                                              1.081


0.26                                                                                0.952


0.31                                                                                  0.690


0.36                                                                                    0.533


0.37                                                                                        0.482


Z.

Aluminium from a N.P.L. report.


Resistivity micrOhm centimetres.   


Soft Aluminium  2.735.


Hard  Aluminium 2.845.



Section for equal conductivity....  Hard drawn copper 1......Aluminium 1.63.


Z.

The original ratings would have been in the 1966 version of the12th edition. Sadly I do not have a copy, but some on here may do and could perhaps scan or photograph the right page.


Correct year of 1966 but that marked the 14th issued on 1st Oct 1966. I can't see reference to Aluminium conductors in 12th or 13th other than mentioned alongside lead as a sheath.


In the 14th of 1966, Table 24 is for P.V.C. non-armoured twin and multicore but starts at 0.03 in2 ie approximately 19.4 mm2.


The 21st August 1970 reprint in metric has Table 24M starting at 16 mm2 which became deleted in the 1st June 1976 issue


Yet to find table for sizes of twin & earth below 16 mm2. This evening's project all being well!


Regards


 BOD

Here's the original pic that was posted: