Whats this cable?

lostinthelight · 11 Feb 2016

Hi, I could not find an intro page so have jumped straight in.
Could anyone please tell me how many amps a roll of cable I have found will carry?
On the white plastic coating it says..plexman- 31. - made to bs 6004, the lable is missing off the reel but I have measured the conductors which are 1.69 mm diameter giving a cross sectional area of 2.24 mm2.
Thanks
litl

RF Lighting · 11 Feb 2016

Depends on how it's installed.

stillp · 11 Feb 2016

lostinthelight said:
cross sectional area of 2.24 mm2

Odd size.

Robin0577 · 11 Feb 2016

Yes, odd indeed.

IF in fact the cable you have is 2.5mm2, which is the nearest standard size, then it's rating can be as much as 27A when clipped direct to a surface or as little as 13.5A when surrounded by thermal insulation on all sides.

Refer to table 7.1(ii) on page 69 of the current IET On Site Guide for the ratings when installed in other ways.

JohnW2 · 11 Feb 2016

lostinthelight said:
On the white plastic coating it says..plexman- 31. - made to bs 6004, the lable is missing off the reel but I have measured the conductors which are 1.69 mm diameter giving a cross sectional area of 2.24 mm2.

What sort of cable/conductors is this - are the conductors solid or stranded, how many conductors are there and is it 'flexible' or 'rigid' (as in house wiring) cable?

As has been said, the dimensions you cite are rather odd. Are you sure your measurement is correct? A solid 2.5mm² conductor, a very common standard size, would have a diameter of about 1.79 mm.

Kind Regards, John

lostinthelight · 11 Feb 2016

Thanks for all your prompt replies, the cable is flat twin and earth with solid wires. I have measures known 2.5 mm2 cable which is why I was confused by this cable . I do quite a bit of metal lathe work so would have thought it unlikely to have measured incorrectly.....but one never knows with eyes aas old as mine

JohnW2 · 11 Feb 2016

lostinthelight said:
Thanks for all your prompt replies, the cable is flat twin and earth with solid wires. I have measures known 2.5 mm2 cable which is why I was confused by this cable . I do quite a bit of metal lathe work so would have thought it unlikely to have measured incorrectly.....but one never knows with eyes aas old as mine

I suppose it's worth checking, just to be sure. Also, if you haven't already done so, it would probably be worth cutting back the cable a few inches and seeing what measurement you then get. What is the diameter of the earth wire?

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.

Kind Regards, John

lostinthelight · 11 Feb 2016

JohnW2 said:
lostinthelight said:

Thanks for all your prompt replies, the cable is flat twin and earth with solid wires. I have measures known 2.5 mm2 cable which is why I was confused by this cable . I do quite a bit of metal lathe work so would have thought it unlikely to have measured incorrectly.....but one never knows with eyes aas old as mine

Click to expand...

I suppose it's worth checking, just to be sure. Also, if you haven't already done so, it would probably be worth cutting back the cable a few inches and seeing what measurement you then get. What is the diameter of the earth wire?

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.

Kind Regards, John

John, I have checked diameter in several places and its the same, the earth wire diameter is 1.32.
I am wondering if the cable could be some sub standard stuff that has slipped through quallity control?
litl

JohnW2 · 11 Feb 2016

lostinthelight said:
John, I have checked diameter in several places and its the same, the earth wire diameter is 1.32. I am wondering if the cable could be some sub standard stuff that has slipped through quallity control?

I rather doubt that. A 1.32 mm diameter earth is about 1.37 mm², which is lower than one would expect (1.5 mm²) with 2.5 mm² T+E, but it is in approximately correct proportion to the 2.24 mm² cable that you appear to have [1.5 mm² x (2.24/2.5) = 1.34 mm²] - so it does rather look as if you may have a deliberately-manufactured 'special'. It seems very unlikely that a manufacturing error would result in both L/N and earth conductors being appreciably under-size.

Kind Regards, John

PBC_1966 · 11 Feb 2016

lostinthelight said:
On the white plastic coating it says..plexman- 31. - made to bs 6004, the lable is missing off the reel

Are you sure there are no other conductor size markings on the sheath?

aaron1987 · 28 Feb 2016

With regards to cable cross sectional areas - the requirement to meet for cable manufacturers is the electrical resistance.
The actual size of the conductor is not a requirement.
So you can get conductors which will not equate to exactly 2.5sqmm in size but still meet the requirements of a 2.5sqmm conductor.
That is not to say that this cable is sized correctly! There is a lot of substandard cable in the UK marketplace and reducing the copper is a great money saver for dodgy cable companies! !

JohnW2 · 28 Feb 2016

aaron1987 said:
- the requirement to meet for cable manufacturers is the electrical resistance. The actual size of the conductor is not a requirement.
So you can get conductors which will not equate to exactly 2.5sqmm in size but still meet the requirements of a 2.5sqmm conductor.

I don't understand that. If the material really is copper then resistance (per unit length) and cross-sectional area are directly related. So, if it's copper and not 2.5 mm², then it can't have the resistance (per unit length) that it would have if it were 2.5 mm² copper.

Kind Regards, John

333rocky333 · 28 Feb 2016

what colour cores, sounds more like its fit for scrap, is white T and E even still made

aaron1987 · 28 Feb 2016

JohnW2 said:
aaron1987 said:

- the requirement to meet for cable manufacturers is the electrical resistance. The actual size of the conductor is not a requirement.
So you can get conductors which will not equate to exactly 2.5sqmm in size but still meet the requirements of a 2.5sqmm conductor.

Click to expand...

I don't understand that. If the material really is copper then resistance (per unit length) and cross-sectional area are directly related. So, if it's copper and not 2.5 mm², then it can't have the resistance (per unit length) that it would have if it were 2.5 mm² copper.

Kind Regards, John

Yes I think your right john - but if you do the maths behind it the max resistance requirements of cable are actually higher than if you calculated it out using coppers resistivity. For example 1.5sqmm if calculated equals about 11.33 ohm/km and the Max resistance for 1.5sqmm cable in British standard is 12.1 ohm/km.
Don't ask me why! But interesting none then less

EFLImpudence · 28 Feb 2016

JohnW2 said:
I don't understand that. If the material really is copper then resistance (per unit length) and cross-sectional area are directly related. So, if it's copper and not 2.5 mm², then it can't have the resistance (per unit length) that it would have if it were 2.5 mm² copper.

Quite.

Plus, of course, it is sold by size, not resistivity.

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Whats this cable?

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