Questionable Conductor Size

Spenny · Aug 1, 2019

I am in the process of installing a 5 core 70mm feeder cable for a DB. 70mm cable lugs are too large for the cores but 50mm fit perfectly. I have taken this up with the cable supplier. Their response was that 50mm lugs are often used om 70mm cores?

Having been in the trade for 41 years I have never heard of this. I normally have to file a taper on to the copper conductors to get lugs to slide on as the fitting is that tight. Now I am told you can easily use a much smaller lug? It makes no sense.

I am of the opinion the cable is under sized yet the OD is 43.3mm which is correct for a 5 core 70mm. Anyone else come across this?

westward10 · Aug 1, 2019

Sounds odd the difference in csa is quite considerable. A 50mm lug should not fit 70mm. What brand is the cable.

Spenny · Aug 1, 2019

westward10 said:
Sounds odd the difference in csa is quite considerable. A 50mm lug should not fit 70mm. What brand is the cable.

EL SEWEDY an Egyptian manufacturer supplied through Cleveland Cables. It is marked as conforming to BS6467 CE

James · Aug 1, 2019

The only time I’ve come across something similar is if the conductor is round and the lugs are designed for shaped core.
But it is sounding suspicious

Spenny · Aug 1, 2019

James the Spark1976 said:
The only time I’ve come across something similar is if the conductor is round and the lugs are designed for shaped core.
But it is sounding suspicious

The conductors are round and I have tried 3 types of round lugs, all with the same result. I crimped a 70 and 50 on to two cuttings, the 50 is perfect the 70 is a shambles.
A 50mm 5 core is not rated for this job as I am installing a 250A breaker so it is critical. The fact that the cable is marked 70mm 5C has me scratching my head.

Bobster · Aug 1, 2019

What measurements have you taken from the actual copper of a core?

They can't hide from a mistake with measuring it.

^Agree with the above, only time I've seen them loose is people mistakenly using the improper lugs for shaped/non shaped cable.

Spenny · Aug 1, 2019

Rob said:
What measurements have you taken from the actual copper of a core?

They can't hide from a mistake with measuring it.

^Agree with the above, only time I've seen them loose is people mistakenly using the improper lugs for shaped/non shaped cable.

The strands are not round so I can't measure the OD accurately. There are 19 of them though so if it's 70mm each should be 3.68 mm. If it's 50 they would be 2.63mm. A strand fits a 2.5mm crimp perfectly.

Spenny · Aug 1, 2019

This is one of the "70mm" conductors used as an earth bond.

westward10 · Aug 1, 2019

If your pic is showing a 70mm then it should not go into a 50mm lug.

Bobster · Aug 1, 2019

I'd put money on that being 50mm or slightly less actually, notice the wings forming on the side of the lug where it's crimped. This shows an improper match between cable/lug/crimp die.

Sparky Pat · Aug 1, 2019

Be interesting to know what BASEC say about it.

westward10 · Aug 1, 2019

What happens when you use a 70mm lug with a 70mm die.

snowhead · Aug 1, 2019

This gives the impression El Sewedy are compliant with BASEC, but with no reference to the quoted BS 6467CE

Egytech Cables (El Sewedy) | BASEC

Find all the BASEC product and system approvals that are currently active for Egytech Cables (El Sewedy). Download Egytech Cables (El Sewedy) relevant certificates approved by BASEC.

www.basec.org.uk

Bobster · Aug 1, 2019

It's an odd standard to reference for a cable

BS 6467
Electrical apparatus with protection by enclosure for use in the presence of combustible dusts. Specification for apparatus

Spenny · Aug 1, 2019

This is the official line from the wholesaler. Data sheet supplied.

The conductor is an compacted conductor.

FYI - A compact stranded conductor is a round or sector conductor having all layers stranded in the same direction and rolled to a predetermined ideal shape. The finished conductor is smooth on the surface and contains practically no interstices or air spaces. This results in a smaller diameter.

I can confirm from the Conductor Resistance on the Test Certification that the cable is 70mm..

westward10 · Aug 1, 2019

They have worked miracles to slim down a 70mm so it fits a 50mm lug.

Spenny · Aug 1, 2019

I will ductor the length tomorrow and calculate the resistance value expected. This just does not add up to me.

static zap · Aug 1, 2019

Spenny said:
I will ductor the length tomorrow and calculate the resistance value expected. This just does not add up to me.

I like it ,if they have squashed the air out,without making it brittle locally.

James · Aug 1, 2019

static zap said:
I like it ,if they have squashed the air out,without making it brittle locally.

So similar to using shaped conductors rather than round to get a smaller overall diameter on the multi core cable, they have taken a stranded single core and run it through a series of rolls so the strands become shaped.

Bobster · Aug 1, 2019

James the Spark1976 said:
So similar to using shaped conductors rather than round to get a smaller overall diameter on the multi core cable, they have taken a stranded single core and run it through a series of rolls so the strands become shaped.

Yes but shaped conductors still have a CSA of 70mm, shaping them only improves the overall diameter of the cable.

This clearly is not a 70mm cable.

westward10 · Aug 1, 2019

This is a 50 next to a 70 so it would require some magic to reduce one to the other without affecting its csa.

snowhead · Aug 1, 2019

westward10 said:
They have worked miracles to slim down a 70mm so it fits a 50mm lug.

And then go to the trouble of padding out the whole cable to the same overall diameter as a 70mm.

Lucien Nunes · Aug 2, 2019

As you'll soon be in a position to test the resistance there's little point doing what I was going to suggest which was to cut the ends of an offcut carefully square, measure the length, strip the insulation, weigh the copper and determine the CSA from the density.

A 70mm² solid conductor is only 9.44mm diameter and the ideal compacted conductor is as close to this as possible. Datasheets for a couple of 50mm² terminals give the cable socket ID as 9.6 and 10mm respectively, so it is theoretically possible for a compacted 70mm² to fit a 50mm² lug, although I too am surprised it fits that easily.

davesparks · Aug 2, 2019

I've noticed a trend for compacted conductors getting to be an increasingly sloppy fit in lugs, it doesn't inspire confidence.
I always ask for correct lugs to be supplied with a cable wherever possible, yet still they turn up loose.

Strima · Aug 2, 2019

We were supplied with some 10mm hybrid cable (fibre in the same sheath) and very few 10mm crimps fit correctly, turned out it was 8 AWG cable from China.