how to measure csa

[hercule]

Hi there, I've not posted much before but been reading old threads and picking up advice from this forum for a while - most problems I've come across somebody else has already asked and been answered.

I've got my NIC assessment this week and now starting to brick it.

Simple question - how do I work out what csa cable has been used?

I'm adding a socket to a ring circuit - r1 and rn readings are fine, but r2 is way too high (compared to others). Im goign to check all sockets for loose connections or terminations onto pvc etc, but I've just realised that the cpc looked smaller than normal. it's 2.5mm t&e (probably 20 years old). What is the normal way to measure the csa to put it on the cert?

the difference is much to high to be just down to 1.0mm instead of 1.5mm cpc, but it started me thinking...

Cheers for any help

Just remembered - there is an extra cpc in some of the sockets I've opened as well as the 2 from the ring. supplementary bonding? what else could they be for?

 

[SPARTYKUS]

hercule

my way, a while ago, was to have a little pack (say 8 inches long, with the ends bared) of every size of T+E and meter tail and single, with it's size indelibly marked on it, so I could visually compare it.

Sometimes it is very very hard to just look at a cable and know!

I find that is the best way. Visual proof!

I still have them BTW elastic banded together.

 

[stansmith]

r2 reading should be 1.67 times higher than r1 and rn on a 2.5mm t+e with a 1.5mm cpc

 

[stansmith]

hercule

my way, a while ago, was to have a little pack (say 8 inches long, with the ends bared) of every size of T+E and meter tail and single, with it's size indelibly marked on it, so I could visually compare it.

Sometimes it is very very hard to just look at a cable and know!

I find that is the best way. Visual proof!

I still have them BTW elastic banded together.

good idea i have the same touble but identifying the larger size cables especially

 

[SPARTYKUS]

good idea i have the same touble but identifying the larger size cables especially

depends on the stella-age the night before.

seriously it can be hard to just look can't it, we are looking at bl00dy cables all day and they all blur into one sometimes.

 

[johnboy6083]

for me, im reasonably good, when ive got loads opf different sizes on the same job. The problem comes, when you have to identify a single conductor, with no other cables to give you an indication. Also struggle with say round conductors to triangular ones.

 

[hercule]

Nice idea Spartykus - the longer I was looking at this cpc the more I was sure it was smaller than 1.5mm and I haven't got a clue how old it is and don't know if 2.5mm t&e might have had 1.0mm cpc years ago - I was going mad. All i needed to do was compare it to some 1.5mm and that would have been it.

 

[MarkieSparkie]

If it is a single solid core you can measure it with a micrometer or vernier caliper and work out the cross sectional area from the diameter.

 

[HandySparks]

If it is a single solid core you can measure it with a micrometer or vernier caliper and work out the cross sectional area from the diameter.

And if it's stranded, work out the csa of one strand and multiply by the number of strands.

For example, 7 strands of 1.35mm dia:
The formula is pi x d² / 4
So 3.142 x 1.35 x 1.35 / 4 = 1.43mm²
x 7 strands = 10.02mm²
So 10mm².

However, it's unlikely that you'll get a spot on answer. A small error measuring the diameter gives a large error on the csa figure.
You can get digital calipers very cheaply nowadays, even on special offer from places like Lidl !

 

[tlangdon12]

Re: how to measure csa - stranded conductors

If you measure the diameter of three strands at three different positions around each strand, and use the average, you will be much less likely to arrive at a calculated CSA that is very far away from the true CSA.

 

[johnboy6083]

be aware that CSA is nominal. It is calculated by current carrying capacity, not by its actual area. Therefore, you may have 2 different manufacturers who produce similar cable, both labels say 3g1.5 . however one may be slightly larger. however, they are both rated for extcly the same current ect.

 

[SPARTYKUS]

be aware that CSA is nominal. It is calculated by current carrying capacity, not by its actual area. Therefore, you may have 2 different manufacturers who produce similar cable, both labels say 3g1.5 . however one may be slightly larger. however, they are both rated for extcly the same current ect.

didn't know that. Ta.

 

[stonejenson]

You'd think there would be a 1:1 scale printed credit card sized reference card that had all sizes on it, singles with & without insulation, and T&E you could just hold up to the cable and get a simple identifiable size comparison. If there is such a thing, where can I get one, if there isn't Copyright ME! You heard it here first!

 

[telectrix]

you get a bit of alli sheet metal.drill a few holes. then shove cable end into whichever hole it fits. eureka.

 

[AndyL]

Hercule, you should be able to work out the difference in resistance by the ratio of the cables

So for 2.5/1.5 cable its 1.67 times higher and for 2.5/1.0 it will be 2.5 times higher and yes some older cables did have 2.5 lives and 1.0 CPC