Cable sizes?

[Greg]

Over the past 4 or 5 years I have been noticing a rather worrying trend regarding conductor sizes.

10 years ago if I looked at conductor sizes I could tell the size straight off the bat. Over the past 5 years this is getting more difficult.

I am now refering to gp wire, twin & earth, norsk/surfix and armoured cables.

Is it just me that is going loopy or are other guys finding the same things.

To give you an example I bought some 6mm twin and earth and stripped the ends. Now if I look at it and guess I straight away think it is 4mm. But it came from a 6mm roll. A 6mm lug fits rather loosley and a 4mm lug goes on quite easily. The cable definately came from a roll marked as 6mm.

Another problem I have is the earth sizes on surfix and norsk cable.

I also notice that the insulation is getting thinner and thinner.

Now I brought this up at the wholesaler where I buy my material from earlier in the week and they told me they had also been noticing it.

Is this cable manufactured locally or does it come from China?

[Justloadit]

If it has the SABS mark on it then it should be local, and should be verified that it is according to specifications.

[Greg]

The SABS mark does not carry much weight in my books. Apparently the SABS organization is one big disaster. They were talking about it on 702 2 weeks back.

[murdock]

i agree...same thing with the pvc boxes...you fit a no1 compression push in gland and even if you put the glue on thick it is still so loose that it just keeps falling out...even tried silicon.

another issue i found yesterday is the cheap DBs supplied with chint products...ever tried to fit a 16 mm wire into the neutral bar...holes are tooo small...yet they have an sabs stamp...absolute rubbish...but as i will say again if they cant even get the electrical policing right how on this earth would they be able to control the influx of crap from china or where ever it comes from.

[Sparks]

Yip, new SA standards. I have also noticed and wondered. That is what happens when school leavers go to university and then come out after a few years with a piece of paper demanding huge salaries to redesign things they have no experience of. Maybe they intend to reduce the size of the 16mm too. As for SABS, who, what, where?

[Dave A]

No chance that this is a case of someone just changing the labels?

[Greg]

No Dave.

I notice this on complete new rolls of cable.

I have even seen a council inspector make a contractor replace a new piece of 120mm 4 core SWA because he was not happy with the thickness of the insulation. The insulation was very thin.

I just seem to notice it to often.

I bought rolls of 2.5mm gp wire where the red and black were different makes. The black was far smaller than the red in terms of outside diameter. In fact when I first saw the black I said to them I wanted 2.5mm and they said that it was 2.5mm. Even when stripped the black looked smaller.

I don't know maybe I have shocked myself one to many times over the years.

[Justloadit]

Maybe you need to send a roll to SABS for testing then.In the weight and measurements, if a client complains, they are out there in a flash, maybe it just needs a phone call to action a call out. The inspectors are not the same for enforcement and monitoring, so it could be that the monitors are slack.

[AndyD]

I have even seen a council inspector make a contractor replace a new piece of 120mm 4 core SWA because he was not happy with the thickness of the insulation. The insulation was very thin.

Electricians and especially inspectors should know that the insulation of a cable isn't specified as a specific thickness, it's specified as requiring a particular resistance at a given length at a given voltage. It doesn't matter what size wire or cable it is and it doesn't matter how thin the insulation looks, if it passes an IR test then it's compliant.

I bought rolls of 2.5mm gp wire where the red and black were different makes. The black was far smaller than the red in terms of outside diameter. In fact when I first saw the black I said to them I wanted 2.5mm and they said that it was 2.5mm. Even when stripped the black looked smaller.

If it's a single core wire it's very easy to measure if it's the correct thickness conductor.


Diameter = 2x √area/π

Example the diameter of a 2.5mm˛ wire should be;

2x √2.5/3.14159

Diameter = 1.784mm

Measure your 2.5mm˛ wire with a vernier and if it's less than 1.8mm diameter at any point along its length then it should be returned to supplier.

With a multistrand wire I would treat the stranded pack of wires as a single conductor and it should pass the same criteria but I'm not sure, there might be a formula involved to accommodate the effect of the air spaces between the conductors.

[sparkydelux]

I was told by a supplier in the UK that the copper supplies are running low(globally), and eventually we will have NO copper left. So what the manufacturers have been doing, is still supplying you with a 6mm cable, but actually it will be 5.65 or 5.75, its marginal, and still has the capability of holding current, just 'trimmed down'. They also increased the insulation size to mimic a proper 6mm cable size.
I though it was also a load of nonsense until I took an old piece of 6mm I pulled from a rewire and measured (vernier) it against a new piece of 6mm. It still complies, unfortunately when we looking for a 6mm we should really be looking for a 5.75 cable or less.

The cable sizes drop across the board too.

Wait until SA will have to change its colours to Brown (L1), Blue (N), Black(L2),and Grey(L3) (like the rest of Europe) so colour blind people can be electricians too. Oh, its coming. Eventually.

Its all changing at some point!