Talk:Electrical wiring in the United Kingdom

The ring

We have a Part P'er living up the road from us, and a neighbour into DIY mentioned that there had been talk of ditching the ring method, as it inherently relies on the ring being complete / fault free for the T&E to carry the loads the sockets are rated at. If the ring were to become faulty, one side of it could then potentially end up being overloaded for the standard diameters. Has anyone with their Part P heard about that or know if it's worth mentioning in the section on rings in the article? —Preceding unsigned comment added by 86.166.135.245 (talk) 02:50, 14 November 2010 (UTC)

Its a false argument for 2 reasons.

1. One side of the cable only is able to carry the load
2. A poor connection in a ring circuit is perfectly safe, a poor connection in a radial is liable to result in a fire.

There are a lot of criticisms of rings without comparing the effects in radials, which are in almost all cases far worse. Just hows how illogical people are. Tabby (talk) 07:58, 27 January 2011 (UTC)

- "A poor connection in a ring circuit is perfectly safe, a poor connection in a radial is liable to result in a fire."

Not true at all. A poor connection in a ring is NOT perfectly safe - At least not for the standard U.K. ring. The cable used is not rated to carry the full 30 or 32A of the protective device; in fact the Wiring Regs. require only that with appropriate deratings applied (for grouping, thermal insulation etc.) it is capable of carrying 20A. A poor connection on a ring can thus result in a cable rated at only 20A being left to carry up to 30A. Even without the problems of a poor connection, it's entirely possible for part of the ring to be overloaded by connecting heavy loads close to the distribution board on one side of the ring. 91.125.155.122 (talk) 23:33, 2 August 2011 (UTC)

Another advantage of a radial is that if a live or neutral connection fails, the circuit will not work, whereas a ring with the same fault will probably go unnoticed and thus create electro-magnetic fields and risk over-load. On the plus side, there is a 'spare' earth cable should one fail on a ring main. Lighting circuits are always radial circuits, so there is no reason to suggest that a properly designed radial circuit is inherently dangerous. 87.113.198.19 (talk) 17:37, 13 December 2013 (UTC)

Supply voltage

This section of the article is vague and out of date. It reads, in part, Since 1960, the supply voltage in UK domestic premises has been 240 V AC (RMS) at 50 Hz. Okay, that's fine…what was it before 1960? It also says electricity suppliers can work with an asymmetric voltage tolerance of 230 V+10%-6% (216.2-253 V). This was supposed to be widened to 230 V ±10% (207-253 V), but the time of this change has been put back repeatedly and currently sits in 2008 (BS 7697). It's now 2009…what's the status of this? —Scheinwerfermann ^T·_C07:07, 23 January 2009 (UTC) A random measurement on my rural village supply on a Sunday evening at 9.40pm local time (21 March 2010) showed 247V. G1MFG (talk)G1MFG —Preceding undated comment added 21:45, 21 March 2010 (UTC).

http://wiki.diyfaq.org.uk/index.php?title=Electricity_Basics#230v_or_240v explains the situation from 1960 to now.

Before 1960 there were multiple standards in use. Most places were anything from 200v to 250v 50Hz, but some were 110v. Its common to see transformer tappings for 200,220,230,240,250v on 1950s & 60s equipment. Tabby (talk) 00:33, 26 January 2011 (UTC)

"Since 1960, the supply voltage in UK domestic premises has been 240 V AC (RMS) at 50 Hz."

This statement is not merely vague, it's wrong. Standardization at 240V across the whole country wasn't achieved until the early 1970's, so there were still some areas with supplies of nominal voltages other than 240V well after 1960, with corresponding 3-wire 1-phase and 3-phase voltages. Although they gradually became less common, D.C. supplies also existed into the 1960's in some places. PBC1966 (talk) 18:04, 8 February 2011 (UTC)

You know what to do. Write it and cite it. --Wtshymanski (talk) 18:41, 8 February 2011 (UTC)

The available transformer tappings and their disappearance from subsequent were little to do with the range of supply voltages then available. In spite of many people's beliefs to the contrary, non 240 volt systems still persist in the UK. Many suburbs of large cities were installed at 250 volts and despite a reluctance of supply companies to admit it, they still are 250 volt (the reluctance is primarily due to the non availability of 250 volt light bulbs). A part of West London really is 230 volt (but distributed as 115 - 0 - 115, an experimental system). This is allowable because even 250 volt systems fall within the permitted tolerance band of the nominally 230 volt supply (but only by a couple of volts). I am not aware of any other variations.

The transformer tappings (and not always transformer - some were taps on a resistor) were solely provided for thermionic valve (vacuum tube) equipment where the heater circuits were very particular about the voltage from which they were run. Nearly everything else (including the thermionic valve HT circuits) were much less fussy and would operate from any supply betwenn 200 and 250 volts.

DC systems survived in the UK longer than you may have believed. Fleet Street in London had a DC supply (generated by Bankside Power Station) right up until it was decommisioned in 1981, and then subsequently provided by locally installed transformer/recitifier units). This was to power the antique (1920's era) hot metal type machines that the unions insisted that the newspapers had to use (because they were very labour intensive). It was the inevitable migration to the docklands areas and the adoption of desktop publishing systems that ended that particular requirement. I am not aware of any large area DC mains distribution system in use today, though local systems are still common (colleges and universities; laboratories etc. etc.) 86.180.161.250 (talk) 13:23, 5 February 2013 (UTC)

Colour Harmonisation dates and table

87.113.116.186 (talk) 11:50, 1 December 2009 (UTC)KO If the colours were harmonised in 2004, why does the table show the colours changing Pre-2004 ????? from memory the colour changes came into force jan 2005, so the table should read Pre-2005

---

That table also omits all mention of earlier standards, such as the use of white instead of yellow up until 1964. The history of flex color coding is also rather more convoluted than suggested, with white continuing in use for some years after it had been replaced by yellow in fixed cabling, and green/yellow being introduced as an alternative to plain green several years before the adoption of brown/blue in place of red/back.

The section about D.C. color coding could also use some clarification. For 3-wire systems mentioned, the old standard was red for positive outer, white (or yellow) for negative outer, and black for middle wire (usually earthed). The negative outer was changed to blue in 1966. But for a 2-wire system derived from a 3-wire distribution network, as in the case of a normal residential supply, the 2-wire installation standard specified red and black, with black for the earthed side of the supply and red for the "live" side, regardless of whether the house was fed from the positive or negative side of the 3-wire system. So yes, there was potential for confusion, but in houses fed from the negative side of the 3-wire system, the coding was actually red for negative and black for positive, with the positive side being earthed. PBC1966 (talk) 18:55, 8 February 2011 (UTC)

Earth conductor insulation, in Circuit Design section

"The earthing conductor is supplied uninsulated for a number of reasons, primarily because it may be considered safer that way. If the insulation of the live/neutral wire becomes damaged due to intrusion by a foreign object (such as a nail/screw) or by fire or heat (caused by short circuit or poor installation), then the wire is more likely to earth itself and in doing so either trip the RCD or burn the fuse out by drawing too much current. "

This is not true. If the CPC (earth wire) were insulated, the distance from the copper to the top outer surface of the cable would be exactly the same as it is now, hence there is no difference in penetration performance.

"Some may argue that insulating the earth conductor would unnecessarily increase the cost, weight, size and rigidity of the cable"

Insulating it would necessarily result in a wider cable, thus more total pvc is used, and one extra moulding process is used to insulate the CPC. I dont see any justification for the phrase 'some may argue that.'

"There is some confusion as to why the third earthing conductor is supplied uninsulated, however the general consensus is for ease of terminating."

I find this an odd view. In a capitalist world, an insulated CPC would cost more due to

• the increased cable size and thus pvc use
• the extra moulding step
• the increased carriage costs due to larger cable dimensions

Now, why would anyone pay a higher price for a cable with no significant advantage? Selling it would be a death blow for any business.

L&N need to be double insulated to avoid risk of shock & fire. There is no reason to add such insulation to earthed metal. Tabby (talk) 00:28, 26 January 2011 (UTC)

Article currently says: "Some may argue that insulating the earth conductor would unnecessarily increase the cost, weight, size and rigidity of the cable.[citation needed]"

So... is there anyone that claims that adding pvc insulation to the cpc would NOT increase cost, size and weight? Tabby (talk) 13:57, 8 May 2011 (UTC)

Additional info in search of a definitive solution

The CPC does not carry current under normal, non-fault, conditions (apart from a tiny functional earth current from filters and switched-mode power supplies in IT equipment) whereas L & N carry the full load current. The CPC is there to provide a reference earth potential (effectively zero volts) so unless the earth continuity is compromised (or there is a fault to earth), it is hard to get a shock from it. Indeed, it is connected to all exposed conductive parts of any equipment it protects to keep them at (safely near to) earth potential. Since it is "safe" for the CPC to have reduced insulation, economic arguments are allowed to come into play. (Note that the CPC has to be insulated with earth sleeving at terminations to prevent it shorting on other conductors before it enters the earth terminal.)

The IEE Wiring Regulations (BS 7671:2008) have an appendix giving references for all other British standards used in it. It would be worthwhile looking up the standard for twin-and-earth cable because in this case, the Wiring Regs defer to it whereas they would ordinarily not condone the practice of leaving off the insulation. Sorry I haven't got an up-to-date copy at the moment or I might be able to find specific regulations and give a better reference.
Peter Riches (talk) 23:12, 6 February 2011 (UTC)

Part P & 12v

"One of the many quirks of Part P is that in some cases the installation of 12V downlighters is notifiable where as the installation of 240V mains downlighters isn't. This appears strange but it's because 12V downlighters draw high currents and that combined with the wrong choice of wire could lead to a fire."

Illogical... both 12v and mains downlighters can and do cause fires, so this is not the reason for the discrimination between them. Tabby (talk) 14:00, 8 May 2011 (UTC)

The official rules about what's notifiable versus what's not notifiable are full of inconsistencies and illogicalities. Typical committee-inspired nonsense which makes absolutely no sense whatsoever. 87.114.73.16 (talk) 22:25, 24 August 2013 (UTC)

Plug fuse confusion

Article now says: "In the case of non-permanently connected domestic equipment, a socket rated at 13 A is attached to the ring circuit, into which a fused plug may be inserted. The fuse protects the contacts (including any switch contacts) and the equipment flex. There are two benefits to this arrangement. Firstly with low power equipment a flex with a low current rating (and therefore small diameter) can be used. Secondly, if the equipment is moved to a different socket, it will remain protected by the same (hopefully correct) fuse. The disadvantage is that despite warnings to the contrary people often use a fuse rated at too high a current, or even wrap a blown fuse in aluminium foil, meaning that under fault conditions the contacts and flex will be subjected to anything up to the maximum ring circuit current. This is likely to cause a fire."

This is confused.

1. 13A sockets are never fitted to ring mains, they're used on ring circuits - I've corrected that. A ring main is something else.
2. All appliances are required to be safe with a BS1362 13A mains fuse. Only some historic equipment may be non-compliant
3. The advantage of keeping an individual fuse with its associated appliance was originally to do with fuse rating, but no longer is. The current advantage is that if a faulty appliance blows its fuse, the user won't get exposed to the risk situation a 2nd/3rd time by plugging it in elsewhere.
4. There is no such a thing in Britain as a mains plug fuse rated at too high a current for an appliance
5. The above passage fails to define or clarify 'maximum ring circuit current', and most readers will think that means either 13A or 30/32A. In practice its usually over a thousand amps, and upto 6000A.
6. A dead short fault carrying this maximum current isn't a significant fire risk, installations are designed to handle this if necessary. Fuse or MCB operate so fast under these conditions that the i^2t isn't sufficient to set things alight. And in case of total MCB failure, The BS88 fuse acts to disconnect the whole installation. Fire is a problem with much lower overcurrents, where disconnect times are greatly prolonged, and total energy dissipation much greater.

Tabby (talk) 15:16, 8 May 2011 (UTC)

Now I'm confused. I thought a 'ring main' was the informal term for a ring final circuit. Ie a circuit into which you connect your BS1363 plugs, so what IS a ring main then?87.113.198.19 (talk) 17:47, 13 December 2013 (UTC)

User:Tabby does much to muddy the waters as far as electrical things work, especially, electrical protection. If someone uses a foil covered fuse at an appliance plug, the circuit protection will operate, as it is supposed to, on short circuit or thermal overload. The idea of a ring circuit is what is installed in most domestic places in the UK, although, places like this are slowly moving towards radial circuits, because of better circuit design and protection available (ie, CB's vs Fuses). Also, what Tabby is talking about is Prospective Short Circuit Current, which depending upon how close you are to your supply transformer, this current could be as little as 3000A, could be as large as 15,000A. A ring main is what the supply authority in your area uses to supply electricity to each block of houses, it is fused at each "take-off", to your and everyones houses down the road, each house is spread in sets of 3 over three phases. Trumpy (talk) 05:29, 28 February 2016 (UTC)

Trumpy (talk) wrote: The idea of a ring circuit is what is installed in most domestic places in the UK, although, places like this are slowly moving towards radial circuits, because of better circuit design and protection available (ie, CB's vs Fuses). It is not the "idea" that is installed! Both ring and radial final circuits are in use in the UK, they are selected according to what is appropriate in any given situation. There is no difference in the protection methods used, only the rating of the protection, 20A for radial with sockets connected, 32A for the ring. FF-UK (talk) 22:54, 28 February 2016 (UTC)

Merge

I propose that the contents of Consumer mains wiring be merged into this article, since that article is almost entirely about wiring in the UK. After the merge, however, that article should be redirected to Electrical wiring since the title is too generic to redirect here.--Srleffler (talk) 04:34, 13 July 2012 (UTC)

• Support since the suggested merge source is strictly about UK practice and somewhat overlaps the contents of this article anyway. --Wtshymanski (talk) 18:58, 14 July 2012 (UTC)

Merge complete.--Srleffler (talk) 04:39, 25 August 2012 (UTC)

Historical D.C. systems

The article says

Direct current mains are now of historical interest in the UK but the colour-coding is red for positive and black for negative.

I believe someone may have assumed this from that fact that non mains wired DC uses this colour coding (example: the colours of test leads for test meters and battery connectors in portable systems). In reality, it was certainly not the case for mains distribution. DC used to be distributed as a three wire system from the generating station (i.e. -200V - 0 - +200V the centre conductor being earthed at the source). Where a building was supplied with a single pole supply, the colours used were RED for the LIVE wire and BLACK for the earthed wire, regardless of the polarity of the live wire. It was not considered necessary to identify the polarity of the live wire because virtually all the loads available at this time would operate correctly regardless of the polarity of the supply (being confined to incandescent lamps; electric heating systems and series D.C. motors). Someone wishing to charge batteries from DC mains (for example) would have to ascertain the polarity before installing the charging system. A 1920 electrical book tells me that this was fairly easy to do by simply dipping the two wires in a mild salt solution (no health and safety here!). The wire with the most number of bubbles was connected to the negative pole.

By contrast, early US systems had no specified standard, but generally used Red for the positive wire and Black for the negative regardless of which was actually earthed. This arrangement made it impossible to identify which was the live wire by mere inspection alone (though the live wire was usually the one routed through the metering system). Later the US settled on White for the earthed wire and Red for a positive live wire or black for a negative live wire.

Where all three wires were available in an installation, the colours were Red (+200V), Black (0) and Grey (-200V) in the UK. The US merely extended the two wire scheme into Red (+ve), White (0) and Black (-ve). 86.180.161.250 (talk) 12:46, 5 February 2013 (UTC)

The I.E.E. recommended standard for 3-wire d.c. in the U.K. back in the 1950s was red positive, black middle wire, white negative. In 1964 the white was changed to yellow, mirroring the similar change for the second phase in a.c. systems. Then in 1966, it was changed to red positive, black middle wire, blue negative. Then when the European flex colours were introduced circa 1970 is became even more complicated. 87.114.73.16 (talk) 22:22, 24 August 2013 (UTC)

Now edited to reflect the above and remove the incorrect grey reference. Also removed the specific reference to +/-200V, since the I.E.E. colour code applied to 3-wire d.c. systems of any voltage level (although most public supplies were from 200/400 to 250/500V). 87.114.73.16 (talk) 13:00, 25 August 2013 (UTC)

Selection of conductors and circuit breakers

For a non-electrical person - but someone who wants to find out more - I felt there was a bit of 'assumed knowledge' required to read certain parts of this article. In particular I found it hard to understand a table where, within an electrical context, there is "Capacity" as a column heading but it has Amps "(A)" as its units rather than Farads ...and then the contents of the column is in Watts, square metres or tonnes! This would benefit from some clearer narrative. — Preceding unsigned comment added by 213.152.245.252 (talk) 11:47, 16 September 2013 (UTC)

Farads are a measure of capacitance. Probably the units in the table are mixed or muddly because they are based on BS 7671 which is probably even more confusing.87.113.198.19 (talk) 17:52, 13 December 2013 (UTC)

Capacity in the table heading is short for current carrying capacity. GrahamN-UK (talk) 20:20, 12 February 2014 (UTC)

Article needs cleanup and improvement

While the article is quite detailed, the detail covers up a lack of organisation and patchy coverage. The main issues for me:

• Title is "Electrical wiring in the UK", but focuses almost exclusively on just two areas of it: regulatory + domestic / low voltage. Non-domestic and industrial? 3 phase? High voltage? Ultra low voltage? All types of electrical wiring that are not for power transmission (data wiring for example)? Other?

• There is pretty much no history section (even if brief), cross references to older standards or other background. I'd expect an article like this to have some way to read the background or history. We have a good-ish article on this at AC power plugs and sockets - British and related types but the historical information there isn't hinted at here, even though it's relevant.

• The regulatory section is very large (compared to other sections) which seems a bit disproportionate, and is somewhat artificially split from "legal" even though they overlap greatly in focus and content. Ideally I think "legal" and "regulatory" should probably go together to make one main section of the article, but the length of this section, compared to length given to other aspects of the topic, feels a bit excessive.

I'm not sure how best to fix/improve these, as "UK electrical wiring" is a very broad topic area, and has quite distinct sub-topics. Perhaps make this into an umbrella article which briefly covers key points and then links to sub-articles for more detailed coverage of topics such as "electrical voltages and cables in the UK", "history of electrical wiring in the UK", "domestic and single-phase wiring in the UK", "industrial and commercial wiring in the UK", and "legal and regulatory framework of electrical wiring in the UK"? Each of those could cover an article easily, and perhaps some of these already exist.

Thoughts on how best to improve our coverage of the topic? FT2 ^{(Talk | email)} 20:09, 1 May 2015 (UTC)

The way to go on this is to make it definitely known that it is building wiring at low voltage, as per the electrical wiring page. Note that the navbox has been edited to enable this focus, which was dipping into HV and distribution. Dougsim (talk)