Imperial cable

[APE37]

Hi guys,
Just after some info regarding old imperial 7/.029 twin and earth cable. Is the cpc in it 3/.029 or 3/.36?
looking to extend a ring final circuit and have come across imperial stranded 7 strands 7/.029 and not sure if cpc is 3/.029 or 3/.036.
Unfortunately not got measuring caliper yet (ordered one) as this is the first time I have come across it and just trying to work out if it is ok to extend it.
Thanks for all help, and if I dont get to say before, Merry Xmas and happy new year to you all.
All the best

 

[Engineer54]

It's going to be a 3/029 CPC.....

 

[Besoeker]

Hi guys,
Just after some info regarding old imperial 7/.029 twin and earth cable. Is the cpc in it 3/.029 or 3/.36?
looking to extend a ring final circuit and have come across imperial stranded 7 strands 7/.029 and not sure if cpc is 3/.029 or 3/.036.
Unfortunately not got measuring caliper yet (ordered one) as this is the first time I have come across it and just trying to work out if it is ok to extend it.
Thanks for all help, and if I dont get to say before, Merry Xmas and happy new year to you all.
All the best

Don't know if this is any help.
By calculation
3/.029 = 1.3mm[SUP]2
[/SUP]7/.029 = 3.0mm[SUP]2
[/SUP]3/.036 = 2.0mm[SUP]2
[/SUP]7/.044 = 6.9mm[SUP]2[/SUP][SUP]

E&OE
[/SUP]

 

[Pete999]

Hi guys,
Just after some info regarding old imperial 7/.029 twin and earth cable. Is the cpc in it 3/.029 or 3/.36?
looking to extend a ring final circuit and have come across imperial stranded 7 strands 7/.029 and not sure if cpc is 3/.029 or 3/.036.
Unfortunately not got measuring caliper yet (ordered one) as this is the first time I have come across it and just trying to work out if it is ok to extend it.
Thanks for all help, and if I dont get to say before, Merry Xmas and happy new year to you all.
All the best

Crikey now you are asking, not sure think it was 3/029

 

[Knobhead]

1/0.044	0.97	mm
3/0.029	1.29	mm
3/0.036	1.94	mm
7/0.029	2.9	mm
7/0.036	4.51	mm
7/0.044	6.45	mm
7/0.052	9.35	mm
7/0.064	14.51	mm
19/0.044	17.50	mm
19/0.052	25.37	mm
19/0.064	39.38	mm

 

[telectrix]

and far superior to the crap we get palmed off with today.

 

[APE37]

Hi guys,
Thanks for the replies. Just wondering if I can be cheeky and ask if anyone has any info on the mV/A/m to work out volt drop on this type of cable plus resistance per meter as I have read that it is different to the values in the regs book? I have taken some end to end measurements and found that the R1+R2 should be around 0.26ohm by r1+r2/4 plus Ze at 0.10 and my addition that i propose in 2.5 is 0.01. It is only around a meter and a half as the old socket is at floor level and the customer wants me to extend up for 2 switched fused spurs for laundry equipment, but one may not be used as they may be getting a washer/dryer all in one. so I have worked out that the Zs will be 0.37 and fault current will be 621.62A and using adiabatic with 0.01 disconnection I need a minimum of 0.54mm2 cpc and so if the cpc is 3/0.029 this equiates to 1.29mm2 so would be good to use. Insulation resistance is +200 between all conductors and circuit is protected by a BS 61009 Type c RCBO Just not sure on the volt drop value and resistance per meter value to use to work out the size of the ring and the volt drop as not able to find any info on them and read that this cable has different values. I would guess that it will be ok as the circuit is in a flat and not too big, but I want to make sure it is ok before I commit to using the existing circuit. Once again thanks for all your help.

 

[Engineer54]

You're overthinking this one. If this was a 2.5mm ring with a 1.5mm CPC you wouldn't give it a second thought in this small flat. So why are you worrying about a 7/029 T&E with a 3/029 CPC??

 

[Besoeker]

1/0.044	0.97	mm
3/0.029	1.29	mm
3/0.036	1.94	mm
7/0.029	2.9	mm
7/0.036	4.51	mm
7/0.044	6.45	mm
7/0.052	9.35	mm
7/0.064	14.51	mm
19/0.044	17.50	mm
19/0.052	25.37	mm
19/0.064	39.38	mm

Not sure about the all the numbers..........
Take 7/0.044 for example.
0.044 is the diameter, in inches, of a single strand.
That is 0.044*25.4 = 1.1176 mm diameter.
Area, from Pi()D[SUP]2[/SUP]/4 =is thus 0.981mm[SUP]2[/SUP]
Total area is then 7*0.981 = 6.867mm[SUP]2


[/SUP]

 

[Knobhead]

Can't say I was that bothered to work it out. I just looked it up.

 

[Besoeker]

Can't say I was that bothered to work it out. I just looked it up.

I had assumed so. But when it didn't agree with the figures I'd calculated earlier I double checked them.
And still got the same result.

 

[APE37]

You're overthinking this one. If this was a 2.5mm ring with a 1.5mm CPC you wouldn't give it a second thought in this small flat. So why are you worrying about a 7/029 T&E with a 3/029 CPC??

Hi eng 54. Thanks for the slap round the head. Seems all ok and yes I probably am overthinking. Just wanted to ensure all is ok before I commit to install as not worked with the old imperial before, apart from rip out for rewires. So thanks for your point, and will carry out said works tomorrow.

 

[telectrix]

assume the cable is modern 2.5/1.5. with imperial cable, you'll be on the right side.

 

[Lucien Nunes]

There was some 7/.029 with 3/.036 earth (they hadn't invented the term CPC then), I have some and it's listed in one of my cable catalogues. But the difference between .029 and 0.036 strands is obvious to the naked eye, so if the CPC strands look like the L & N, it'll be bog standard 3/.029 earth.

 

[Paul P]

Two thoughts, 2.5 always had 1.0 cpc back in the early 80's. I am told they also made stranded 2.5 as well. Not sure of the cpc size of that.