Cable size and live wire colour change

[Fleetwood]

Hi Can anyone remember which came first, the change of cable size to metric from imperial or the change to brown for live conductor? I've come across a cooker supply cable with new colour code of Brown,Blue + Earth but it is 7 stranded. Difficult to tell it it is 7/029 or 7/036. Could be the later as it seems a little light for 7/044. It feeds via a 32a MCB. Anyone recall using stranded new colour twin and earth?

 

[kingeri]

New (and old) colour 4mm upwards is stranded! Imperial cables went out way before harmonised colours came in!

 

[kingeri]

Likely to be 6mm if feeding a cooker

 

[Fleetwood]

Thanks Kingeri. Bit concerned it could be 4mm as it's terminated in a 13a socket as the cooker outlet box. It's in a rented house that my daughter's new boy friend is taking on and they need to know what wattage combined oven/hob they can buy. They have their eye on a 10.5Kw Beco and with diversity I've worked out that it should be ok with a 6mm cable fed from a 32A MCB. Having said that, this Beco has an unusual suggested cable spec. ie 5 X 1.5mm, 3 X 2.5mm or equivalent. That is suggesting a 7.5 mm cable (which there isn't). 10mm seems an overkill for situation seeing as how with diversity we about 21A flowing. Any comments would be appreciated.

 

[Richard Burns]

Take along a 2cm length of 6mm and one of 4mm and compare the size of the cores.
6mm is fine on a 32A for a cooker up to 15kW

 

[Fleetwood]

Am I correct in thinking that the 10.5Kw oven/hob is still ok even if the cable turns out to be 4mm? This oven needs to be hard wired so the 13a socket needs to be changed to a normal control box?

 

[kingeri]

No offence, but I can tell the difference between 4mm and 6mm at a glance! 10.5kw with diversity would need 6mm. And yes, you need a cooker isolator, certainly not a socket outlet!

 

[Fleetwood]

Sorry Kingeri, I'm misleading you drastically - had a long day. There is a cooker control unit with combined socket but what I meant was that there was a 13a socket as a connection box. This the one the cooker is connected to.

 

[sparky-s-w]

do you mean the cooker switch feeds a twin socket

 

[sparky-s-w]

and are you concerned with the main cable to the cooker switch, the cable from the cooker switch to the socket, or both

 

[Fleetwood]

do you mean the cooker switch feeds a twin socket

Yes,that's right

- - - Updated - - -

do you mean the cooker switch feeds a twin socket

Yes,that's right

 

[Fleetwood]

and are you concerned with the main cable to the cooker switch, the cable from the cooker switch to the socket, or both

The cable to both

 

[kingeri]

Sorry, I'm confused. At the end of the day you want to end up with a 6mm feed to either a cooker control or a cooker control with integrated socket, and that's it. Nothing else. You don't want any additional cable going to a socket. It should be a radial circuit that terminates at the cooker switch. Or am I misunderstanding?

 

[Fleetwood]

Kingeri I will recap. The circuit is fed from a 32A MCB with 6mm(?) cable to a cooker control with integrated socket and then down to a further switched socket. This is what I think should be a normal connection box. (The type that can take up to 2 10mm cables ) Don't know why its a socket unless the previous oven was without an electric hob. This is possible as there is a gas connection point in close proximity so there may have been a gas hob. Therefore then that oven may have used a 13A plug.
This new Beco, being 10.5 KW has to be hard wired so I need a proper connection box. Would have thought that the cable is 6mm as the MCB is rated 32A. THis is too high for 4mm cable. Just wanted to be sure cable is 6mm because new oven is 10.5KW. If the cable for some reason is 4mm, this would have been ok with a low wattage oven on a plug - even if the MCB was wrongly rated at 32A - but certainly not ok for 10.5 oven/hob.

 

[MarkieSparkie]

[FONT=&amp]Imperial T+E Cable sizes were phased out in the late 1960s but still available up until the introduction of 14th Edition:1966+A3:1970
Harmonised Colours implemented from March 2004 onward with the introduction of BS7671:2001+A2:2004[/FONT]

 

[Des 56]

Quote
MCB is rated 32A. THis is too high for 4mm cable.

?​

 

[Fleetwood]

Well 4mm cable has less current carrying capacity then 32A.

 

[kingeri]

Depends on the installation method.......4mm can carry 37amps if clipped direct or embedded directly in plaster. 4mm radials on 32a breakers are quite common, usually for socket circuits.

Your question seems to hinge on deciding what size cable you have, something which we can't answer remotely on a forum. Take a sample of it to the wholesaler or even to the big orange shed and compare it to 4mm and 6mm on sale there! Or post some to me and I'll tell you what it is! 4mm is a bit bigger than 2.5mm.....6mm is quite a bit bigger......as I said earlier sparks can usually tell the difference at a glance. You could measure one of the strands and calculate the csa that way, if you have the right equipment (a vernier caliper).

 

[Fleetwood]

So on that basis then we could connect the 10.5KW oven even if the cable is 4mm

 

[HandySparks]

Well 4mm cable has less current carrying capacity then 32A.

If clipped direct or buried in non thermally insulating wall, CCC is 37A. How is it installed?

(Edit: not quick enough!)