2.5mm cable is stranded?

[holmslaw]

..

 

[sparkwright]

What colour are the original wires in the installation? If they are also red and black he may have been trying to match the colours up, whilst using up some old stock.

 

[Paul_C]

my mums place was built in the early 60s and that's all stranded 2.5mm on the ring finals.

Metric size cable didn't come into use until circa 1970, so it wouldn't be 2.5 sq. mm. Pre-metric rings were normally wired with 7/.029 (with 3/.036 earth).

 

[EFLImpudence]

The cable is black / red ( guy installed it about a year ago])

 

[jmac80]

hi guys
yes the original cables are single core black and red.
will take a picture tomorrow

 

[Adam_151]

Metric size cable didn't come into use until circa 1970, so it wouldn't be 2.5 sq. mm. Pre-metric rings were normally wired with 7/.029 (with 3/.036 earth).

Wasn't that a 3/.029 Earth (1.3mm²) ? ....3/0.036 was nearer 2mm²

 

[Paul_C]

Wasn't that a 3/.029 Earth (1.3mm²) ?

No, the earth size was chosen to be a minimum of half the c.s.a. of the circuit conductors, so 3/.029 would have been too small. 3/.036 was the smallest standard size which satisfied the requirements for 7/.029 circuit conductors.

The standard make-ups were:

1/.044 with 1/.044 earth
3/.029 with 1/.044 earth
3/.036 with 1/.044 earth
7/.029 with 3/.036 earth
7/.036 with 7/.029 earth
7/.044 with 7/.036 earth
7/.052 with 7/.044 earth
7/.064 with 7/.052 earth

(See Table D.2 in the 14th edition or Table 5 in the 13th, if you have copies.)

 

[YorksSparks]

my mums place was built in the early 60s and that's all stranded 2.5mm on the ring finals.

Metric size cable didn't come into use until circa 1970, so it wouldn't be 2.5 sq. mm. Pre-metric rings were normally wired with 7/.029 (with 3/.036 earth).

Before I deleted it, I had edited it to say 2.5mm's Imperial equivalent. As you say, 7/0.29. Mind you, I've made a few alterations since it was first put in...

 

[Adam_151]

No, the earth size was chosen to be a minimum of half the c.s.a. of the circuit conductors, so 3/.029 would have been too small. 3/.036 was the smallest standard size which satisfied the requirements for 7/.029 circuit conductors.

The standard make-ups were:

1/.044 with 1/.044 earth
3/.029 with 1/.044 earth
3/.036 with 1/.044 earth
7/.029 with 3/.036 earth
7/.036 with 7/.029 earth
7/.044 with 7/.036 earth
7/.052 with 7/.044 earth
7/.064 with 7/.052 earth

You're right of course, I'd got it into my head that it was 3/.029 (1.3mm) and then this got rounded down to 1mm with metricification and then got corrected to 1.5mm when they realised it failed for thermal withstand on a re-wireable.

But I suppose there was a copper shortage at the time, and a jump from nearly 2mm to 1mm was probably not questioned!

 

[SimonH2]

Its normal, 2.5 comes as solid core or stranded, 7 strands. Stranded is more flexible and stronger than solid core.

Really, I'd love to know where I could buy stranded from as I've never seen anything but solid in metric sizes. Going solid was definitely a retrograde step and I suspect the manufacturers used the change as an excuse to cut manufacturing costs

Metric size cable didn't come into use until circa 1970, so it wouldn't be 2.5 sq. mm. Pre-metric rings were normally wired with 7/.029 (with 3/.036 earth).

Ahh nostalgia, 7/029 - the only pre-metric cable size I know.

 

[Paul_C]

Really, I'd love to know where I could buy stranded from as I've never seen anything but solid in metric sizes.

I know that Doncaster Cables for one makes 2.5 T&E in stranded form. You'll probably pay a little more to have it ordered specially by your wholesaler though.

 

[kai]

Ryness is where I bought some 2.5. stranded cables (red & black), it may be worth calling into a Ryness to see whether they have stranded 2.5. cable in stock.