Cable rating re: Wiring Matters Ask questions and find answers to many subjects relating to electrics and electrical work

[ericmark]

After reading the article to clarify in “Wiring Matters” I am confused.
BS 7919, BS 6500, HO7RN-F, CENELEC HD22.4 S4, and 3183YAG all refer to flex often referred to as Arctic cable.
The voltage rating is either 300/500 volt or 450/750 volt and the article rightly pointed out that the peak voltage of a 230/400 volt RMS supply is 325/565 peak so the 300/500 volt rated cable should only be used on reduced low voltage supplies. And also the temperature varies with some cable only rated at 5 deg C where some manufactures state -20 to -30 degrees C.
However when one tries to work out which is which a very different problem arises with Eland Cables saying their BS7919, CENELEC HD22.4 S4, HO7RNF cable is rated 450/750V and Batt Cables saying their BS 6500 cable is rated 300/500V.
The Wiring Matters article gives a table on page 15 where BS 7919 Table 44 is for 110v and BS 6500 is for up to 300Vac single phase or 500Vac three phase.
Both cables are available in blue and yellow and both are found around caravan sites, and marinas where the proprietor is responsible for site safety but rarely responsible for providing the cable and between this and the way the BS7671:2008 asked for 2.5mm² cable at 25 meters long yet 1.5mm² cable is rated at 16A.
This means the guy has to decide if he is going to challenge his tenants over the suitability of the flex.
If it was ones own responsibility for all then one could use SY cable and have done with it but a little different when one has to condemn cable, which may be OK.
I would like to hear opinions on this?

[ericmark]

After making enquiries else where it was pointed out twin and earth cable is also rated 300/500Vac so if blue flex is not allowed neither is twin and earth we would need to use Ali-tube which is rated 600/1000Vac?

[sparx]

hi Eric,
read same artical plus another on subject elsewhere,
Surely if the BS ratings quote for Root Mean Square values they must be suitable for the Peak to peak values by default? .....or maybe not, however domestic twin with CPC are to BS 6004 table 4D5, which quotes 450/750v, not 300/500v,
BS6500 is for 'flexible cords ..for use with appliances & equipment intended for domestic, office and similar environments', not sure outdoor 'artic cables come in that catagory anyway,
BS 7919 covers 'flexible cablesrated up to 450/750v for use with appliances & equipment intended for industrial & similar environments, so don't see a problem myself..
regards as ever Sparx

[ericmark]

I was surprise when the rating of twin and earth was pointed out and I went to Batt and Eland cable web sites to check and yes rated 300v. However I could not find any reference as to if voltage referred to RMS or Peak valves and in view of so many cables which we use on 230v being rated at 300v I am now thinking 300v refers to RMS.

Question remains should we worry about using cable rated 300v on a 230vac RMS supply.

I would never use a capacitor rated 300v on a 230vac supply so why should I use cable rated 300v? But only option would be Ali-tube cable and good as it seems getting any with out placing a huge order is not easy.

I am sure the British Standard would give the answer but at the price charged I have no intention of buying a copy.

Personally I think most Electricians no longer take any notice of Mark Coles after the last article in wiring matters and look at it and say to themselves "Oh it's him again".

However he could be right? And can you imagine the cost if it was decided that houses should not be wired in 300v twin & earth cable and electrician were instructed to correct it? Somehow I think the insurance would also be unlikely to cover and we would be looking at the biggest rise in bankruptcy ever seen.

I did check to see if 220vac would come within the 300v limit but no it would need to be 212vac.

He has potential stood on a hornets nest. I am sure in Spring he will be publishing some get out and will have to back track. But of course it is not the only item which the new 17th Edition has highlighted where we may have been getting it wrong for years.

In 1962 I did not need to earth lights. Mind you I was only 11 so not really into electrics then. But things do change and in the main for better. Not seen an open knife switch on LV since 1972 and even then it was not in daily use. And good job. OK as battery isolator but not on low voltage.

73 Eric