Replacing ailing electric installation

[Gerd Busker]

We knew our installation was bad when we moved in, but then I really started looking and found:

2 Illegal drop lines from ring mains, one of which melted when I touched it (without blowing a fuse).

All original cabling (rubber/cloth covered?) falls apart when touched One circuit had melted into its metal piping A blowout in the fusebox because some crud fell from the top onto the power rail. All these issues have been secured, I have experience (and qualifications) with electrics in the netherlands (very different domestic installation philosophy using only 16A radial circuits) and studied the IEE onsite guide.

I have replaced all the cable runs in metal with appropriate 1.5/2.5/6.0 mm2 PVC packaged or separate runs + ground. I no longer want to rely on the rusty metal piping to provide a good earth. I can't find any reference to using metal trunking as earth in the IEE on-site guide, so I guess this is no longer allowed? The connections had mostly rusted off in our house in any case...

The electricity company man has already moved the meter for me, so there now is space to install a modern distributor board instead of the old crap.

There are 6 circuits, 3 of which (2x kitchen + 1 near bathroom) I would like to protect with an RCD. Is the best approach to get a consumer unit with an RCD protected rail, or just get 3 RCDO type fuses for these circuits? Where should I buy these things in the UK? B&Q have started stocking, but I'd be a bit happier checking what good makes are. MK?

Any advice/discussion etc. appreciated.

BTW, any ideas on how to clear a particularly badly blocked bit of metal truncking (in concrete)? I got the cables out, but there is molten rubber/cloth in the way, about 3 feet from the socket.

Gerd.

ps. This house use to be let. I'm surprised nobody died during that time. pps. Replacing cabling I found: loose live wires where no attempt made to connect to socket. "Twist together and pray" type connections. "Forgot to tighten one of the screws" type connections (which miraculously passed a standard socket test!)

[Andy Hall]

Well, Meneer, it sounds as though you have a lot of work on your hands....

One thing is that if you prefer, there is nothing to stop you wiring your power circuits with 16A radial connection in either a daisy chain or other topology.

However, it is much more common to use the BS1363 30 or 32A ring circuit.

There is nothing to prevent you using metal conduit although it is normally used with single conductors and not PVC twin/earth cable.

If it's really bad, I would rip it out or leave it and use T&E. You could replace with plastic conduit if you like but again that is normally used with singles.

You can do either. A split load consumer unit is popular but of course anything causing a trip downstream of the RCD takes everything on any downstream circuit. You need to have any circuit with outlets that could be used for portable equipment outside protected by an RCD. RCBOs do give a more flexible arrangement for sure but are more expensive. As a general rule, go for a consumer unit with some spare ways. You are sure to need them eventually and the boxes are cheap.

MK is probably the best make on the market, and I tend to use their products exclusively. B&Q is not a good source though because they are quite expensive. Try on line tlc-direct.co.uk or better still find an electrical wholesaler like WF or Newey and Eyre and go along with your shopping list. If you buy a lot of product, they will give you a good discounted project price.

Don't bother. Bypass using it if you can.

.andy

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[Lurch]

On Wed, 26 May 2004 15:28:10 +0100, Gerd Busker strung together this:

That's where it starts!

It is allowed, but for a domestic property is unneccessary. As long as there is continuity, to satisfactory levels as described in BS7671, then it can be used, obviiously where it has alll worn\corroded away this would be difficult! In your case it is easier to install new cabling with twin and earth than attempting to repair\replace the conduits.

The most common method is a split load consumer unit, where half the circuits are protected by RCD and the other other half aren't. A better way of doing it is using a non-RCD unit and providing RCBOs for individual circuits, but this is a more expensive way of doing the job.

I'd go and find a local electrical wholesaler, they're more than likely going to have a better range and helpful staff. As for makes it all depends what you're after, if money is no object then I would fit MK throughout. As a cheaper alternative Crabtree are also a good quality make but are considerably cheaper than MK.

Probably not worth re-using it, it'll be easier to re-run the cable down the wall to the socket and bypass the conduits altogether.

[Christian McArdle]

I'd replace the whole lot with twin & earth cable. It is no longer current practice to install cables in conduit . Although some still use them when buried in wall plaster, this is not required, provided you follow the guidance about where in the wall to bury the cable.

When rewiring, don't reuse any cable or component from the old system. Buy new cable, socket outlets, switches, junction boxes and light fittings. The old ones are well past their use by date and replacements are cheap, especially in bulk.

RCBOs are best. Split load consumer unit with RCD is much cheaper. Non-split consumer unit with RCD is no longer permitted. Your lights shouldn't be RCD protected, unless you have a TT system, where they must be protected by a

100mA time delay RCD. You should protect all your socket outlets with an RCD, except the one used by the fridge/freezer. This isn't a requirement of the regulations, but is best practice.

16A Radial circuits like those you are used to are permitted. Indeed, with suitable cable, you may run similar circuits at 20A or 32A, too, as the appliance plugs have fuses in them. However, ring circuits are more common in this country and have certain (occassionally controversial) safety benefits, such as having the earth provided via 2 paths.

You might as well rewire using the full British style methods, as the British fixed wiring standards are the best in the world. (US is about the worst...)

Christian.

[Lurch]

On Wed, 26 May 2004 17:55:06 +0100, "Christian McArdle" strung together this:

Yes they are, in the instance of a TT system where the whole CU is covered by a 100mA RCD and the outdoor sockets are RCD protected, or scenarios closely matching that.

[N. Thornton]

Its bad, but compared to places like India, Kuala Lumpur, Thailand etc, lousy American standards are positively reassuring. I saw a pitcure once of an Indian hotel install where it was simply impossible to work out what cable went to where. It was a jumbled tangle of maybe

100+ cables, all sorts of diffrent kinds of wire, and when I say jumbled I mean literally jumbled, lots of slack all interwoven into a big loose hairdo of wires a couple of feet across. Fun.

Regards, NT

[Mike Tomlinson]

In article , Christian McArdle writes

There's a rogue's photo gallery at

on the Photo/Violations forums.) Some real lulus there.

[Christian McArdle]

I touched on this earlier in the piece. Basically, on a TT system, the choices are the same as a TN system, but the isolator incomer should be replaced by a time delay 100mA RCD.

This could lead to a non-split consumer unit with an RCD and no RCBOs, but only if you didn't have any outsides (i.e. upstairs flat) and no requirement to RCD anything in a bathroom. However, it would be much safer in such circumstances to install a split load/RCBO arrangement for all socket circuits (except fridge/freezer), as you do not want a socket circuit earth fault (quite likely event) to take out the lights. By having an immediate action 30mA on socket circuits, the 100mA time delay won't blow and remove lighting.

Christian.

[Lurch]

On Thu, 27 May 2004 09:55:34 +0100, "Christian McArdle" strung together this:

That's not quite what I was saying, I was meaning with outdoor sockets having their own 30mA RCD built in, so that would be tripped first before the 100mA. Pretty much the same as RCBOs but doesn't take out any additional sockets. Anyway, we're straying a bit from the path here! I was just pointing out that it is allowed, under the right circumstances, it's just not very common.

[Jim Michaels]

On Wed, 26 May 2004 17:55:06 +0100, "Christian McArdle" Snip...

In what respect are U.S. wiring standards vastly inferior?

Several accepted U.K. practices fall below U.S. minimums.

U.S. standards with few exceptions appear to meet U.K. minimums. "Wirenut" splices and the configuration of outlets/plugs seem to be the items that would not pass U.K. inspection. Remove SPAMX from email address

[N. Thornton]

Yes a few good ones there, but unfortunately most of it I couldnt make head nor tail of. All American, with endless moaning about people not following some American wiring code or other.

I guess this would be the all time classic:

NT

[Mike Tomlinson]

In article , N. Thornton writes

well, yes, that was kind of the point - Christian was commenting on the crap standard of American domestic wiring. To be honest, you don't have to read the comments, just look at the photos in the URL I gave - have you seen the one of some bloke working on wiring while standing on a metal ladder erected in a swimming pool!? Suicidal.

[Christian McArdle]

Well, at the end of the day, the statistics tell the story. Compared to the US, there are practically no injuries from fixed wiring installations in comparison. If you would like to argue about a particular practice, please get the ball rolling, as I'm always one for a good argument, particularly when it provides new viewpoints and perspectives.

Christian.

[Jim Michaels]

'There are three kinds of lies: Lies, damned lies and statistics.'

I have spent some time trying to find relevant statistics and I have had no success finding comparable statistics. If anyone has sources please respond either to the group or via email.

In the US there are no federal regulations regarding wiring (and building codes in general) it is left to local regulation. In urban areas the NEC model code, or a local variant, has been enforced for many decades. Until recently the enforcement in rural areas has been poor to non-existant.

Generally US regulations only apply to new work or renovations and existing installations that once met code are allowed to continue without updating.

From my perspective our practices seem safe. Is there anything specific that seems unsafe from an outside perspective?

In the Chicago Metro area local codes exceed the NEC and generally require all residential work to conform to commercial standards. For example, all wiring must be in metallic conduit. It is hard to imagine fixed wiring installed to this code resulting in loss of life.

In any situation, Cowboy work that does not meet any standard can result in grave danger.

Footnote 1: In his autobiography, Twain wrote: "Figures often beguile me, particularly when I have the arranging of them myself; in which case the remark attributed to Disraeli would often apply with justice and force: 'There are three kinds of lies: Lies, damned lies and statistics.'" However, no one has been able to find evidence that the British Prime Minister ever made such a remark. As noted in Ralph Keyes's Nice Guys Finish Seventh, Harper Collins, 1992, investigators have discovered the following comment by a member of the (British) Royal Statistical Society: "We may quote to one another with a chuckle the words of the Wise Statesman, lies, damned lies, statistics..." (Journal of the Royal Statistical Society, 1896). The similarity between the comments is unmistakable, but any connection to Twain or Disraeli is unknown.

Footnote 2: The National Electric Code (NEC) has been sponsored by the National Fire Protection Association (NFPA) since 1911.

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