Running 6mm cable along outside of house?

[ARWadsworth]

I have done that. I suspect that the gravel boards will outlive the wooden shed that the cable supplied.

[AL_n]

John Rumm wrote in news: [e-mail]:

Thanks for the input/suggestions. When I buried that 22mm water pipe, there is a section where a vehicle could concievably cross. I lined the base of that section of trench with pea gravel and laid concrete blocks over the top. I'll ease up the concrete blocks and now lay the SWA underneath too.

The alternative possibility was to run the came overhead from the house to the garage. But that looks ugly.

Al

[Spamlet]

It depends on the alignment of house and garage, but our supply comes from the first floor of the house straight through conduit to a high corner of the garage - which is only about 6ft away - so the cable is all out of the way above where anyone is likely to kick it.

On the other hand our gas pipes (not put in by us) are just tacked along the house wall and could easily be kicked off, though they haven't been in 20 odd years.

S

[george [dicegeorge]]

Is it OK to use red and black, I thought it all has to be blue and brown these days?

[g]

[Andy Burns]

No, but ...

[Andy Wade]

The cable you have there is almost certainly 2.5 mm^2, not 4 mm^2. 2.5 is the largest size where you'll normally find single solid cores (of diameter 1.78 mm not 2 mm). '4 mil' SWA would have 7-strand conductors (7/0.85).

BS 6346 is the standard for PVC insulated SWA which does tend to be a little larger than for the same CSA with XLPE insulation (BS 5467) which is what is normally used nowadays (and for the last ~20 years, in fact).

The current rating for a single-phase circuit in 2.5 PVC SWA is 28 amps clipped direct, or 29 amps where buried. As others have said it's voltage drop that may be the size-determining factor.

But you still need 30 mA RCD protection for the sockets in the shed.

[AL_n]

Andy Wade wrote in news: [e-mail]:

I think you are right. I examined the cores under a magnifying glass and they are under 2mm in diameter.

OK - thanks. When were RCD consumer units introduced? The reason I ask is that the unit in my house is probably a early 1980s vintage and orginally had wire fuses. I fitted MCBs when I bought the house six months ago. I think someone once suggested I should swap the box for a RCD one, but warned me that I'd experience a lot more trippings of the circuit breakers when there was no actual fault to speak of, so I left it as it was to avoid the hassle. My logic was, that I couldn't remember hearing of anyone having a life threatening accident due to the failure of a fuse or circuit breaker prior to the introduction of RCD boxes, so why change it end experience more nuisance MCB trippings.

I can put a small RCD box in the garage no problem. Should I be worried that the house has no RCD?

Al

[John Rumm]

Might be worth sticking a vernier or micrometer on the actual wire core to make an accurate measurement to be sure....

Yup, well spotted - I did not see the BS 6346 bit at the time...

Odd thing is the overall diameters on the smaller sizes of two core don't seem as different as one might expect if table 7 in BS 6346 is to be believed:

CSA PVC Diameter XLPE Diameter

1.5 12.3 12.1 2.5 13.6 13.6 4 15.1 14.7 6 16.5 15.9 10 20.1 18.0 16 21.9 20.4

Needless to say 2.5 and 4 mil being the hardest to differentiate!

(PVC diameter from BS 6346 Table 7, XLPE Diameter from BS 5467 Table 6)

[John Rumm]

They started to be common from about the mid 80's IIRC (during the time of the 15th edition of the wiring regs)

You may have been getting a mixed message there. Swapping from fuses to MCBs can raise the nuisance trip level on things like lighting circuits, due to the high (but brief) current surge that can occur when a filament lamp fails. Nuisance tripping of a MCB on a socket circuit is going to be pretty rare unless you are starting up large induction motors or transformers!

Nuisance tripping of a RCD (assuming the basic installation design is sound, and there are not too many circuits protected by the same device) is usually indicative of a deeper problem. So basically it ought not happen if everything is working ok.

Having a RCD will not effect the trip rate of a MCB at all (no way it can). It will introduce a separate and different trip mechanism. However it is one that is particularly well suited to preventing serious injury.

RCDs are particularly valuable for protecting supplies used for power tools in the garden etc, where the risk of exposure to a hazardous voltage is greater in the first place (e.g. mowed, & hedge trimmed flexes etc), and the risks from shock are far greater (e.g. in a damp environment with a very good personal connection to earth). Here RCDs have resulted in notable reduction in serious injuries.

(due to the generally high standards that we apply to domestic electrical installations in this country, fatalities resulting from electrocution are typically very low (usually less than 20/year), most of which come from accidents with appliances. However it is a fairly safe bet that the presence of a working RCD would prevent most of those)

That is a deeper question ;-)

Start by having a read of:

get the background.

Let's start from the assumption that you have a RCD protected plug-in extension lead or similar, so that you can safely take power outside. This is the first place RCD protection is a no brainer. If you don't have at least this, then get something. Its up there with smoke alarms as a cheap, worthwhile common sense thing to do.

Now you need to look at the particular risks in your household:

How likely are you or other people in the house to get a shock in the first place?

A reasonably modern wiring install with decent earthing provision[1], with not too many extension leads or stacked socket adaptors floating about the place, and no kids that might decide to play with a socket, probably means relatively little risk while inside (assuming the equipotential bonding is up to scratch in the bathrooms etc).

Various things can increase the risks; if you do plenty of DIY for example, or have a wiring install of questionable integrity and age, or young kids romping about the risks go up. Having a garden or a workshop where you may use power tools raises the risks a bit. If you live out in the sticks and find rodents frequently noshing your cables, or have a thatched roof, then risks increase again. Most of these are not large in themselves (you are statistically far more likely to trip over and break your neck or slip with a carving knife, than go out in a shower of sparks!), but they help form a overall picture.

[1] If you have a TT install, then RCDs become essential.

[Frank Erskine]

It's entirely up to you - it's nobody else's business on your own premises, is it?

[tony sayer]

I'd trade any day a few nuisance trips for hanging across the mains which from personal experience is EXTREMELY PAINFUL let alone somewhat life threatening..

I would. We make it a condition that any plant we work on anywhere and some is located in remote places, has RCD protection and is tested periodically..

As to spurious tripping usually only when there is reason to trip. Electrical leakage in heating elements, Neutral to Earth shorts, and occasional odd trips in thunderstorms and such like.

Some times a lot of Capactive leakage if you have a LOT of IT like equipment around..

Here around one nuisance trip every three years on average;!.

Just fit it, one day you might be rather grateful..,...

[AL_n]

tony sayer wrote in news: [e-mail]:

Thanks. What is the cheapest way to do it (in the house)? Do I need to buy an entire new distribution box with new MCB's - of is there a RCD device that I can install between the Electric meter and the distribution box?

If the former, can anyon recommend a cheap online supplier?

Al

[David Robinson]

Are people here too "polite" to mention Part P to the OP?

New circuit. No RCD. Wrong colour cable.

Just asking...!

Cheers, David.

[Fredxx]

Didn't the OP say he was going to make it a spur off an existing circuit?

[John Rumm]

Probably, yes...

You may be able to get RCBOs for your particular box, in which cas you could protect the socket circuits with one.

You can, but you don't want to. Firstly it does not meet the current requirements for containing a fault by isolating close to the source and leaving other circuits unaffected (i.e. a trip loses power to everything). Secondly, that is a good way to make nuisance trips far more likely.

TLC are pretty good:

[js.b1]

Hmmm....

"The installation of prefabricated, "modular" systems (for example... armoured garden cabling) linked by plug and socket connectors is not notifiable, provided that products are CE-marked and that any final connections in kitchens and special locations are made to existing connection units or points (possibly a 13A socket outlet)". SI2006, p9, part "k.".

So he could legitimately have a Pre-Fab run of Double-Socket glanded off to Flex for thro wall (sleeved), Jn-Box, CW SWA-Gland, SWA, CW SWA- Gland, Jn-Box, Flex for thro wall (sleeved), RCD-plug and plug into a socket.

Indeed I recall such systems being available with armoured and flex attached - not many, but they are out there. More commonly available are outdoor sockets with flex for poking through a wall and connecting to an RCD plug on the inside.

It does not define "prefabricated", which could mean a bloke down the pub, john prescott, yuang dong province of china on a friday etc.

The OP should add RCD protection to the house as soon as possible. For a garage it does without saying. Another note is does the garage have incoming services etc re export of house earth. Nothing to stop the OP putting the Red Black 2-core SWA on Ebay, plenty of people will buy it if and only if he puts postage on it. Just coil it up, band-tie with serial cable ties, tape over the sharp ends, put in a "rubble sack", ship via

or for about =A35.95 to =A36.99 + VAT, so charge the buyer =A35.99 to make things attractive.

[AL_n]

John Rumm wrote in news:w- adndhJ [e-mail]:

another, yes?

Funnily enough, it appear my garage already has some primitive RCD box with big old-fasioned black circuit breakers, but it's rusty and has no cover, so I'll prolly buy a new plastic one to replace it.

Al

[John Rumm]

I would guess that most don't actually give a toss.

I don't recall anyone recommending not using an RCD, and there is nothing wrong with using a new circuit for this application.

As to the "wrong" colour cable its hardly a big issue in this context (i.e. self use rather than supplying to a customer etc). It will have no negative effect on the safety of the installation. It hardly seems like an environmentally sound idea to dispose of cable and then buy it all over again just to get it in a different colour.

Why?

The OP has had the good sense to ask for advice on the best way of doing this, and has received a number of sensible replies with good advice. I (rightly or wrongly) get the impression you seem to be advocating a nanny knows best response consisting of finger waving and a sharp intake of breath.

[js.b1]

Is the OP sure it is single strand, I thought it was always class-2?

1985 1982 PVC SWA 2c was 7-strand even on 1.5mm. If the cable is older than that, check for white slimey deposits on the zinc armour, because it means the ends have been wet and water has tracked into it by thermal cycling.

[John Rumm]

They will all be of an adequate quality certainly - none are going to be unsafe. What varies is the range of accessori1es that will fit, the ease of wiring, the long term availability of parts, aesthetic appearance etc.

MK tend to be very nice in most of these respects, but you pay for the brand. Contactum are not as swish but very much cheaper. Hager and Wylex are somewhere between them etc. There is also a fair bit of badge engineering that goes on, with one maker producing parts badged for another etc.