identifying cable size by eye

[dv6]

Hiya everyone,

Just a quicky. I know Ohms law and calculating your cable size and protective device etc. But how do you know the cable size of a piece of cable visually around your home ? I can see a shower circuit and i can tell staright away its run in a cable much thicker than 2.5mm twin and earth. I am guessing at 10mm. But is there anyway of identifying cable size by sight like this ? Or is it a case of just becoming so familiar with the cable sizes on sight ?

cheers

 

[Adam_151]

You can tell after a while, I did a while ago post up the overal thicknesses of all the sizes of T+cpc, but then we realised that older cables that thicker insulation than what you get these days!

Also, anything 4mm² or above is stranded and anything below is solid, in metric T+cpc cables 99% of the time*

6mm² will have a 2.5mm² cpc and 10mm² a 4mm² cpc, so you can judge 6/10 on cpc stranded or not




* I've seen stranded 2.5mm² t+cpc only once, and it was definatly 2.5 and not 7/.029!

 

[tim west]

One of those things that are hard to quantify, it's really only experience that helps, always look at a cut end if possible, as stated above you can be fooled by thickness of insulation.

 

[davy_owen_88]

 

[tim west]

might give an idea but it doesn't show CSA

 

[davy_owen_88]

It'll give you the diameter of the conductor/s and then pi x r² will give CSA but it was meant as a joke

Anywho, I just measured some 2.5mm² t&e at 1.7mm diameter which gives it's CSA as: 2.27mm² - so I think I'm going to write an angry letter to the robbing b@stards at Copper Cable Company

 

[tim west]

It'll give you the diameter of the conductor/s and then pi x r² will give CSA but it was meant as a joke

Yep same here hence the wink

 

[JiMMySnoW]

Anywho, I just measured some 2.5mm² t&e at 1.7mm diameter which gives it's CSA as: 2.27mm² - so I think I'm going to write an angry letter to the robbing b@stards at Copper Cable Company [/quote

Ha ha made me laugh.

 

[Trazor]

Anywho, I just measured some 2.5mm² t&e at 1.7mm diameter which gives it's CSA as: 2.27mm² - so I think I'm going to write an angry letter to the robbing b@stards at Copper Cable Company [/quote

Ha ha made me laugh.

Nice reply to a thread which is SEVEN years old.

 

[JohnW2]

Nice reply to a thread which is SEVEN years old.

Not quite - a few months to go

Kind Regards, John

 

[RobinClay]

Nine months later.... for some people, it does take a while for the joke to sink in


But I have the same "challenge" It's an old multi-strand twin-&-earth, red, black & green / yellow, all three cores are covered. The skin is the usual white PVC, and the overall size, measured with calipers, is 14mm x 7mm.

So - what's the amperage rating - anyone ? Please ?

 

[stillp]

what's the amperage rating

What's the installation method?

 

[RobinClay]

Thanks. It's ducted behind the render, then lying loose under the floorboards.

 

[ericmark]

I normally got to Batt Cables site to get sizes of outer sheaf, however it does vary manufacturer to manufacturer, since white it may be thermal setting plastic so could be rated at 90°C not 70°C.

It comes down to why do you want to know. I find it hard to condemn other electricians one really needs to get a cable end and try fitting lugs to be 100% sure about size, and stick a soldering iron into the insulation. Same with working out loop impedance and volt drop, unless grossly out one is hard pressed to show some one else got it wrong.

But where you want to add to a circuit one can air on the safe side, so if asked to add a socket one and your not sure you simply say no.

I have plugged in the loop impedance tester and looked at a 1.48Ω reading and considered what to do, however when it was fitted the incomer could have been 0.20Ω and now it's 0.35Ω so can't really blame whoever fitted it.

However what one does do it look at the installation and from the 100's tested before decide if the reading is to be expected or not. For a small house likely further testing will show the ring final has been broken.

I have not seen much flat cable with the earth with insulation already on it. I have seen some really dangerous mistakes, when I was doing heat treatment some one stole a role of cable, this was not standard copper cable and if used on mains would likely go on fire. I would not think this is the case with your cable, but if it was me I would be looking for writing on the cable. Something does seem odd.