Whats this cable?

[stillp]

BS7671 is not a standard for cables. If a standard defines the material, and if the resistivity of that material is known, then there would be no need for it to define ('maximum', or 'minimum', or average, or whatever) resistivity for cables of various CSAs, since those figures would follow automatically from CSA and resistivity - and, has been said, cables are made, sold and labelled by CSA, not resistivity.

The standard is BS6004, but I don't have a copy now. You'd be right if the resistivity of the copper used in cables was a constant, but because the copper isn't pure, and it might not be annealed, the resistivity might be different from that of pure annealed copper.
I once visited a cable manufacturer, who checked the resistance of each reel as a final check on material and diameter being within allowed tolerances. I don't know what the tolerances are for 6242Y, but I'll be at BSI this week and will try to check BS6004.

 

[JohnW2]

The standard is BS6004, but I don't have a copy now. You'd be right if the resistivity of the copper used in cables was a constant, but because the copper isn't pure, and it might not be annealed, the resistivity might be different from that of pure annealed copper.

Fair enough - but, as I said, if the Standard defines the material (maybe it doesn't?), then that, in turn, would define the resistivity.

I once visited a cable manufacturer, who checked the resistance of each reel as a final check on material and diameter being within allowed tolerances.

That makes some sense. However, as you say, two factors (both of which affect resistance) are involved. If the material (and its resistivity) were 'out of spec', but the diameter were also 'out of spec', in the 'opposite' direction, the resistance could be 'correct' - would that cable be compliant on the basis (which I think is what has been suggested) that its resistance was correct?

I don't know what the tolerances are for 6242Y, but I'll be at BSI this week and will try to check BS6004.

Thanks.

Kind Regards, John

 

[PTS2]

Get another roll of 2.5 T&E, using the same measuring tool and the same measuring technique, what's the diameter of the conductors?

 

[ban-all-sheds]

You might, of course, have some sort of 'special' cable, but it's difficult to see why anyone would bother to make a 'special' so close to a standard size.

It might not be special.

It's not an AWG or SWG size, but it could be a standard size somewhere, and a cable maker has used it.

 

[PBC_1966]

Does BS6004 recognize sizes other than 1.0, 1.5, 2.5 sq. mm. etc?

 

[PTS2]

The csa of these cables are nominal values so a bit like mains voltage being stated to be 230v when in practice its allowed to be a bit off. If the measurement is correct then the csa of the relevant cable is approx 2.25mm2 which fits in 2.5+/-10% (just).

 

[stillp]

I now have BS6004, but it refers me to BS EN 60228 for the conductors... Will try to find that later.

 

[JohnW2]

The csa of these cables are nominal values so a bit like mains voltage being stated to be 230v when in practice its allowed to be a bit off. If the measurement is correct then the csa of the relevant cable is approx 2.25mm2 which fits in 2.5+/-10% (just).

Hopefully stillp will soon be able to give us some chapter and verse, but (although I may be wrong!) I would rather doubt that the permitted tolerance on conductor CSA will be anything like as large as ±10%.

Kind Regards, John

 

[ban-all-sheds]

Does BS6004 recognize sizes other than 1.0, 1.5, 2.5 sq. mm. etc?

Dunno.

But it's irrelevant to my point. The cable maker may very well have been untruthful in claiming BS 6004 compliance, but I was responding to John's observation about why would anyone bother to make a special cable so close to a standard size. It might not be a special - it might just be wrongly labelled.

 

[JohnW2]

... I was responding to John's observation about why would anyone bother to make a special cable so close to a standard size. It might not be a special - it might just be wrongly labelled.

Fair enough - but isn't the main issue that the cable is apparently not labelled (correctly or incorrectly) with a claimed CSA?

Kind Regards, John

 

[stillp]

the cable is apparently not labelled (correctly or incorrectly) with a claimed CSA

If that's the case then it does not conform to BS6004!
11.1 External marking The external surface of all cables conforming to this British Standard shall be legibly marked with the following elements: Element Example of marking a) Cable manufacturer Manufacturer’s name and their unique factory identifier NOTE 1 A simplified version of the manufacturer’s name, or a trading name of the manufacturer, may be used in place of the full name. NOTE 2 Any suitable method may be used to unambiguously identify the manufacturer’s factory. NOTE 3 The manufacturer’s own trademark or equivalent may be added but this cannot be used instead of the manufacturer’s name or identifier. b) Electric cable ELECTRIC CABLE c) Voltage designation 300/500 V d) British Standard number BS 6004 2) e) UK cable code 6242Y NOTE 4 The relevant UK cable code is given in Table 3 to Table 6. f) Number of cores, nominal area of conductor and circuit protective conductor as appropriate i) 3 × 1.5 3) ii) 2 × 1.5 + 1.0 4) g) Year of manufacture ZZZZ NOTE 5 The year of manufacture may take the form of the actual year (e.g. 2013) or a coded year identifier assigned by the manufacturer. h) Standard core colour identifier H NOTE 6 See 11.2. The marking of items a) to h) shall be by embossing or indenting on the sheath. The markings shall appear along the axis of the cable in any sequence that is deemed to neither confuse nor conflict. NOTE 7 The order in which the elements of marking appear along the length of the external sheath is not prescribed, but it is preferred that they be in the order a) to h) as shown in this subclause. The letters and figures shall consist of upright, block characters. The distance between the end of one element of the marking and the beginning of the next identical element of the marking shall be not more than 550 mm in accordance with Figure 1. Conformity of the marking shall be checked by visual examination and measurement of at least two sets of elements.

 

[JohnW2]

the cable is apparently not labelled (correctly or incorrectly) with a claimed CSA

If that's the case then it does not conform to BS6004! ...

Interesting. It was the absence of a CSA marking that really gave rise to this thread.

I was going to suggest that maybe the cable was not manufactured for the UK (or any European market), but we are told that one of the few things with which the cable is marked is a reference to BS6004 - so that idea rather goes out of the window!

Kind Regards, John

 

[stillp]

I believe that BS6004, along with other BSs, has credibility on other countries, so maybe the manufacturer sees that marking as a marketing advantage, but doesn't want any breaches to be too easily detected.

 

[stillp]

Right, there seems to be no minimum diameter for copper conductors. There is a maximum (1.9mm for 2.5mm²) diameter for copper solid conductors, and a min & max for aluminium or copper stranded flexible.
The CSA is defined as follows:
2.2 nominal cross-sectional area
value that identifies a particular size of conductor but is not subject to direct measurement
NOTE Each particular size of conductor in this standard is required to meet a maximum resistance value.

The maximum resistance for 2.5mm² plain copper conductors is 7,41Ω/km.

 

[JohnW2]

Right, there seems to be no minimum diameter for copper conductors. There is a maximum (1.9mm for 2.5mm²) diameter for copper solid conductors ...

Interesting. I make that about 2.835mm².

The CSA is defined as follows:
2.2 nominal cross-sectional area
value that identifies a particular size of conductor but is not subject to direct measurement
NOTE Each particular size of conductor in this standard is required to meet a maximum resistance value.

Again, interesting. Surprising though I (and I suspect others) find it, that is, indeed, essentially what aaron1987 said at the start of the discussion.

The maximum resistance for 2.5mm² plain copper conductors is 7,41Ω/km.

is that at 20°C, or what?

Kind Regards, John