Neutrals in cables. seperated from extractor fan wiring ....

27 Jan 2008
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Llanfair Caereinion, Nr Welshpool
United Kingdom
Neutrals in cables.
Not wanting to get the pour guy helix confused I considered is prudent to start a new post.
Ban-all-sheds has raised the idea of having a requirement to include a neutral in all cables.
I see a problem using cables with floating cores and was always taught that unused cores should be earthed to stop the capacitance and transformer effects.
I have worked more on three phase and split phase supplies than on single phase and I have long questioned the use of cable designed for three phase on single phase installations.
I have worked many times with white numbered cores and with some of the cheaper cable it is very easy to lose the markings or miss-read.
As a result I can see why using distinct colours is far easier than using numbered cable.
Many years ago I worked in the automobile trade and in the UK we had a range of base colours and tracers. However as more cars were German built the colour system became replaced with number system 30 live and 31 chassis etc. But quite obvious manufactures have no problem including a trace colour.
So to produce cable with three brown cores with red, yellow, and blue trace should be no problem.
However the yellow artic cable is in the main used on split phase supplies i.e. no neutral so should have brown, black, and yellow/green cores and if the manufactures can’t get that right I think we have no chance to get them to change the colours used in twin and triple and earth cables.
There was a double red core twin an earth available but at an inflated price. And one of the main reasons cable is cheap is the quantity it is made in.
Before the 17th edition I always said how can there be a standard for colours which we should not use anyway when asked what colours should go to which terminal on a two way switch.
However I see that in 17th Edition it refers to using the tri-coloured cable and how it should be sleeved.
However I think they have missed the boat and if any standard was to be adopted then it should have been declared at the same time as we changed cable colour. Many firms have produced their own standard and declared what base colour should be used for neutral in their buildings. And any electrician in their employ either direct or contract is required to follow their rules.
Any standard declared now would be bound to conflict with company policy somewhere.
So personally I think we should leave it as is. And accept that we must check and take nothing for granted.
Appendix 7 tells us with DC systems the line conductors are Brown or Grey which means where there is no Blue core we only have Black we can use for mid point connection. To use a different colour on AC circuits could lead to mistakes and confusion so I will use Black for neutral.
However on the old cable colours where there were two lines and one neutral I can see why people would use brown for neutral and the two blacks for line. I think the move to new colours on cables from Europe has to be better than old system with three phase cable using a Brown and two Blacks. The introduction of Grey is great.
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Having read nozspark, ColJack, and ban-all-sheds comments on original post I would question the Voltage: 300/500v on 624Y Twin & Earth PVC Cable BS6004 A05VVH4-U as peak voltage on a 400v supply is 565v although it also says Standard: BS6004 Electric cables. PVC insulated, nonarmoured cables for voltages up to and including 450/750V, for electric power, lighting and internal wiring.

I can not recall using any for three phase either NYY Cable 600/1000V to VDE0271/0276 or SY Braided Cable (coloured cores) although I do note the latter has same rating as triple and earth. Although it is available as 4 and 5 core which seems a better option to feed any motors.

What I have questioned is the changing from Red, Yellow, Blue or Brown, Black, Grey to Red or Brown when supplying a single phase circuit. To me it would be better not to have a colour change but we are not given option.

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