Black cable for 110v site extension leads?

[KevDIY]

I'm proposing to make a flexible 110v 16A ceeform extension lead from 2.5mm H07RN-F - black rubberised cable. It'll be used for 110v portable power tools from centre-tapped site transformers. IMO its much superior to yellow arctic in terms of handling, and (I believe) also in terms of insulation in damp situations etc.

However, it is definitely not as visible, and potentially the softer insulation may not resist pointy things as well as the yellow stuff. So I'm not sure if it would be acceptable if I ever needed to use it on professional building sites, where I've only ever noticed yellow arctic for 110v extensions.

Does anyone know if this would be rejected, rightly or wrongly, due to not being 'normal' yellow arctic?

Cheers
Kev

 

[Risteard]

Obviously protection against abrasion is very important. However there is no requirement for a 110V reduced low voltage system to utilise yellow flexes throughout, although many may prefer it.

 

[KevDIY]

Great, thanks!

Its a pity they haven't managed to make this stuff in bright yellow and blue (or at least I've not seen it if they have). It seems to get used a great deal in temporary setups and extensions etc, where being more visible would often be useful.

Cheers
Kev

 

[ericmark]

I do agree with you but of course it's down to UV light black is best for outside use.

Be it supply to caravan or 110 volt supplies it would seem we often use the wrong cable HOSRN-F (BS 7919) or equivalent should be used for a caravan try buying it at a caravan shop. Since 110 volt is 55-0-55 the core colours should be Brown, Black and Green/Yellow yet nearly every cable I have wired are Brown and Blue with the exception of when working on the build of Sizewell where we used 3 phase 110 volt splitter boxes and the cable was Brown, Black, Black and green/yellow this was before the second Black was was replaced with grey.

Maybe this month is the time to correct it we do have a blue moon?

 

[KevDIY]

Ha, it would be nice

I'd not thought about the UV, good point, thanks! I'm happier with the black colour now I realise why.

I suppose I could put a black sheath over the blue conductor, but at least its no different to the yellow arctic in that respect so doesn't seem to count against H07RN-F.

I suppose brightly coloured plastic flex/cable is cheaper and more visible, but I much prefer the handling of more flexible leads. By comparison the flexibility of the 'Arctic' stuff is very poor IMO (unless I've always had second-rate stuff anyway), and some of the bog standard orange leads can be truly diabolical to wind up or lay out properly flat without making loops to trip over. If I was a caravanner and had the option of H05RN-F it would be a no-brainer for me!

Thanks for the help,

Cheers
Kev

 

[ekmdgrf]

Doesn't a black cable absorb, rather than reflect UV light?

 

[bernardgreen]

If you are making up the cables, ( ie putting the plugs on the ends, then you could put lengths of yellow heat shrink at intervals along the black cable.

Though that might make things worse if people avoided the yellow bits on the ground and stood instead ( accidently ) on the not so visible black sections of cable.

 

[ekmdgrf]

If you are making up the cables, ( ie putting the plugs on the ends, then you could put lengths of yellow heat shrink at intervals along the black cable.

Though that might make things worse if people avoided the yellow bits on the ground and stood instead ( accidently ) on the not so visible black sections of cable.

Also there is a risk of mistaking it for a stinging insect.

 

[Risteard]

Since 110 volt is 55-0-55 the core colours should be Brown, Black and Green/Yellow yet nearly every cable I have wired are Brown and Blue with the exception of when working on the build of Sizewell where we used 3 phase 110 volt splitter boxes and the cable was Brown, Black, Black and green/yellow this was before the second Black was was replaced with grey.

I disagree. Given that neither core represents phase L2 of a three-phase system I would suggest that the correct core colours are brown, brown and green/yellow.

 

[plugwash]

And I'd say that given one core is definately live, one core is definately earth and one core may or may not be neutral depending on the supply the cable is plugged into that brown/blue/green+yellow is fine.

 

[Risteard]

And I'd say that given one core is definately live, one core is definately earth and one core may or may not be neutral depending on the supply the cable is plugged into that brown/blue/green+yellow is fine.

In a reduced low voltage system neither of the live conductors can be a neutral conductor, only a line/phase conductor.

 

[JohnW2]

In a reduced low voltage system neither of the live conductors can be a neutral conductor, only a line/phase conductor.

Quite so. I think it's also important to remember that one of the main (safety-based) reasons for 'identifying' conductors as "L" and "N" in an installation having an earth-referenced supply is to distinguish between those conductors which normally are at an appreciable potential above earth and those which normally have a potential close to earth. Using blue to identify one 'end' of a 55-0-55 supply would undermine that concept.

Having said that, whether colour identification of conductors is of any appreciable importance within a made-up extension lead is perhaps a somewhat different question.

Kind Regards, John

 

[KevDIY]

Interesting thoughts, thanks everyone.

Yes, my intended application is a typical site supply of 55v-0-55v in which 0 and earth are connected these days, so that means two phase/line conductors at largely equal potential from earth

Though I also fully agree it is entirely down to assumptions about the supply, and I can't dictate 'any' of that in my extension lead (except hopefully the connectors would suggest use at 110v). So perhaps any attempt to colour the conductors appropriately could always be thwarted.

A 110v supply could in theory have one line/phase conductor referenced to earth, although I've never seen that myself. But I have seen fully floating supplies - IMO they made sense before RCDs were prevalent, or perhaps where RCDs may be considered unreliable (not that I'm certain they are reliable or necessary on a 55v-earth potential.). So overall I think probably leaving the conductors 'as is' seems the normal way, or sheathing the blue one in black may be technically more correct..

I find such things a bit annoying TBH; I'm not a qualified electrician but I try to be informed and do things properly, yet there are so many grey areas in the various standards that as a non-professional its hard sometimes, even on things that are common and should be straight forward.

Cheers
Kev

 

[Risteard]

A 110v supply could in theory have one line/phase conductor referenced to earth

It couldn't because were it referenced to Earth then it would not be a line conductor but a neutral conductor.

 

[KevDIY]

Yes, thats kind of what I meant. My 'assumption' is that the extension lead will always be used on a typical 55-0-55 site supply with 0 being referenced to earth. But if the exact same lead was used on a differently referenced 110v supply, one of the line/phase conductors (as I saw it) could actually be a neutral, and I have no control over that.

EDIT: though thats seems a little unlikely in practice; a fully floating supply would perhaps be a greater probability.

Cheers
Kev