Discuss Why Are Incoming Live/Neutral 16mm and Tails From Consumer Unit 25mm in the UK Electrical Forum area at ElectriciansForums.net
When we have NICEIC inspection
It is so over kill with 25mm, just think of the normal length between the cutout and the meter, 300/400 average, hardly a long run. Also now a days, with LED lamps and down lights and how much more efficient appliances are, loads in peoples house are being reduced compared to 15 years ago,
I feel that people are more comfortable installing 25mm2 tails if the primary ocpd is known to be 100amp as a play it safe concept.
You’re probably right Dave.I feel that those people are lacking in the technical knowledge they are supposed to have.
It's not strange at all really Dave. It can be different assessor each time and they all have there little pet hates and ideas of what is right and wrong. My last assessor stated it needs to be 25mm tails whereas the Stroma tech line said use your knowledge as an electrician to determine the size.That's weird, our NICEIC assessor this year was happy with 16mm tails straight from a 200A supply to a switchfuse. I can't see any real difference.
To be fair to the 25mm² people, there is a certain logic in using the largest reasonable cable size in a situation where it's slightly more of a pain to alter for future upgrades (due to being (theoretically) sealed in the meter) than if they were entirely within the customer's equipment.
It's not strange at all really Dave. It can be different assessor each time and they all have there little pet hates and ideas of what is right and wrong. My last assessor stated it needs to be 25mm tails whereas the Stroma tech line said use your knowledge as an electrician to determine the size.
a) This may be foresight for the future without Petrol/Diesel !comments of previous posts that there seems to be this wish to upgrade to 25mm tails regardless.
3 circuits, 32A cooker, 32A ring and 6A lighting. The main cut-out fuse is 60A. New meter been fitted within the past year or two and the tails from the meter to fuse board were obviously replaced at the same time. They are 16mm tails. Personally I see no reason to replace them - Am I wrong?!
The bit that gets me is that within the OSG under 2.2.3.1 Consumer Tails it states on para 2 "Polarity should be indicated by the colour of the insulation and the minimum cable size should be 25mm." The reg no it refers to is 514.3.1 - however this doesn't mention anything about cable size.
I am currently in the process of replacing a customers old re-wireable fuse board. The main cut-out fuse is 60A. They are 16mm tails. Personally I see no reason to replace them - Am I wrong?!
People have already picked several holes in that napit book, it's got several things in like thatIf anyone has a copy of the napit EICR codebreaker book, in there under section 1.4 there is a point about the cross sectional area of the tail between the meter and cu having to be more than the minimum allowed of 25mm2, citing a FI code against a breach of the ESQCR.
Now, this is admittedly only a napit book, but is generally considered to be in line with the 'rules'.
In saying that, I cannot find any reference whatsoever to this in the ESQCR!
Yeah, spotted a few others myself, or bits I disagree with, but just thought I'd mention it as there is lots of documentation out there which imply there is a rule somewhere leaning towards a minimum of 25mm2.People have already picked several holes in that napit book, it's got several things in like that
Mostly the current rating you will see for 16A is part of a multi-cable assembly, even then if you look at 4D2A table method E 'free air' you see 16mm down as 94A and with two separate wires the rating is a bit more.maybe I'm being completely stupid but how are consumer tails sized? alot of people saying 16mm is fine also in the past/years it was acceptable 16mm and 100A fuse ? and just briefly flicked through current carrying capacity tables and 16mm is quite below 100A - what am I missing or doing wrong?
A perfectly good point, and if you are not sure (see @Mark Wright post) then simply fitting 25mm is the easy solution.I don't disagree with any of the points made on 16mm tails, However I would say that most people don't probably want the confrontation with their inspector during the annual assessment and so just choose to install 25mm tails to get the boxes ticked and save themselves all the hassle.
I would get a new assessor, I take it you said ok, then promptly fitted 70mms?That's weird, our NICEIC assessor this year was happy with 16mm tails straight from a 200A supply to a switchfuse. I can't see any real difference.
Not about forgetting or ignoring it is a thing that just doesn't need thinking about, doesn't need remembering and doesn't need calculating doesn't need over complicating.Older installations had 16mm tails fitted because that all they need.
In recent years it has become the norm for people working in the domestic sector to fit 25mm tails regardless of what size is actually required.
This has been fuelled by the IETs picture book which shows diagrams of typical supply and CU setups where 25mm tails are fitted.
So now we have a lot of installations with shiny new CUs and 25mm tails, fed via 16mm tails from the cutout which in turn is fed via a 100 year old paper insulated lead sheathed cables of an imperial size a bit smaller than 16mm.
Why electricians these days seem to forget/ignore the theory, science and regulations and choose to follow the herd like a bunch of sheep I don't know.
Its not a great argument though.There is an argument that using 25mm where 16mm would do is a safety issue in itself. Given the near universal acceptance of 6181Y, IMO there's an argument for saying that many installations are "a bit iffy" due to the strain such stiff cable puts on the terminations and component mountings. With 6381Y, different matter - but then you get into "discussions" with wholesalers who ask "what's wrong with 6181Y - everyone uses it"
Use the now widely available 19 strand stuff, much more flexible. Even the meter fitters have now started using it!There is an argument that using 25mm where 16mm would do is a safety issue in itself. Given the near universal acceptance of 6181Y, IMO there's an argument for saying that many installations are "a bit iffy" due to the strain such stiff cable puts on the terminations and component mountings. With 6381Y, different matter - but then you get into "discussions" with wholesalers who ask "what's wrong with 6181Y - everyone uses it"
I would get a new assessor, I take it you said ok, then promptly fitted 70mms?
Not quite sure on what you base some of your facts and why you choose to make the final comment you doOlder installations had 16mm tails fitted because that all they need.
In recent years it has become the norm for people working in the domestic sector to fit 25mm tails regardless of what size is actually required.
This has been fuelled by the IETs picture book which shows diagrams of typical supply and CU setups where 25mm tails are fitted.
So now we have a lot of installations with shiny new CUs and 25mm tails, fed via 16mm tails from the cutout which in turn is fed via a 100 year old paper insulated lead sheathed cables of an imperial size a bit smaller than 16mm.
Why electricians these days seem to forget/ignore the theory, science and regulations and choose to follow the herd like a bunch of sheep I don't know.
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