Commissioning a ring circuit

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On Mon, 03 Nov 2003 15:55:44 +0000 (GMT), Dave Plowman

Agreed. But then those earlier situations did not take account of increased stupidity in government.
PoP
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Seconded. Working on your own time, not rushing things, and knowing you have your and your family's welfare at stake, you're more likely to do a good job than many electricians doing "small works". (As I understand it, commercial work usually pays a lot better than small domestic jobs, so it's that much harder to get a competent, pride-in-work person to do small domestic jobs. Far from impossible, but a pain.) A little trip along the new ring (before it's powered up!) with a Long Long extension cable plugged into the first socket on the ring (leave the two ends at the CU unconnected), working in sequence and checking for continuity between the terminals at your sockets and those at the end of the extension, will indepedently confirm you have the right connections made; and if you have a low-ohms reading meter, you should be able to see the resistance rise steadily as you work your way further along the ring. That, on top of the FAQ procedure (which is lifted from the On-Site Guide), will be plenty.
There's an affordable piece of "quick-check" gear on the market these days which I find worth having: it's an update of the old "three neons wired between the three pins" jobbie, which includes a basic earth-loop-impedance check. RS sell them at the usual "full-RRP-plus" price as stocknum 436-3456 for 50 quid, so you can probably find them at your friendly electrical trade counter for about 35 quid. (Sparkies will instantly recognise the sound as "the first Martindale of spring" ;-) They'll give a within-10% indication of the earth loop impedance being in one of 6 bands: 0-1.7, 1.7-5, 5-10, 10-100, 100-200, 200-500 ohms; anything over the first two bands is, like, Wrong (even a value over 1.7ohms is cause for some concern). This is not a precision earth impedance checker, but to check your own wiring or that of a house you've just moved in to it's not a bad bit of kit. Obviously, it works on sockets which are powered up, so you do your own multimeter and visual checks on new wiring *first*!
HTH, Stefek
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On Mon, 3 Nov 2003 20:24:16 UTC, snipped-for-privacy@hp.com wrote:

For insulation/continuity, what do people think about this, at 89 quid from TLC?
http://tinyurl.com/ti8t
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Bob Eager
rde at tavi.co.uk
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wrote:

or this one (Stefek mentioned it) http://www.martindale-electric.co.uk/EZE150.pdf
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On Mon, 3 Nov 2003 22:19:37 UTC, "Chris Oates" <none> wrote:

I know he did (I did quote him!). But that's not the same thing....he was showing an inexpensive way to check earth loop impedance. The item I mentioned is complementary, not a replacement - the other major part of the equation.
I've not seen anything else at this price, so opinions are welcome.
--
Bob Eager
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For insulation, it's useful, I s'pose; but the more significant problems on domestic circuits are likely to need low-ohms metering rather than hi-ohms (you want to tell the difference between a solid and a partial screw connection; to tell the difference between the two legs of a ring; and so on). The kit you mention doesn't seem to do that - though the much pricier 255-quid-plus-VAT thing below does. All-in-one meters with low-ohms ranges are a bit thin on the ground, but Fluke do a mid-price one (same sort of price as the insulation tester you mention) which does a reasonable 20-ohms-full-scale, 0.01 nominal resolution, as do Wavetek (T120B - or at least they did ;-) For Regs-conformant-final-testing a 200mA test current is needed; I don't think these multis do that, but they're cheaper than the Robins/Seaward and so on things.
(Pauses to flick through RS catalogue) Hmm, not many cheaper "low ohms" meters to be found here, in fact a dearth. For those with a bit of electrickal skill, making up a Wheatstone bridge with a decade or binary box of low-value reference resistors might be a more affordable way of doing Low Ohmage, as might the more direct route of creating a 200mA constant-current source (hey, may as well use the current the Regs tell us to!) capable of developing, say, 10V, then use the "normal" low-voltage sensitivity of even a cheapie multimeter (2V full scale, nominal 1mV sensitivity) to measure the voltage dropped: each 200mV means 1 ohm, thus allowing quite reasonable sensitivity. Absolute accuracy will be poor, granted; but you'd certainly be able to do the ring-resistance tests with such a rig, and you can calibrate with a decent 0.5ohm wirewound or similar...
Stefek, rambling on.
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On Mon, 3 Nov 2003 22:55:51 UTC, snipped-for-privacy@hp.com wrote:

I agree. The spec sheet (downloadable via link in corner) says there are four ranges, the fourth being:
OHMS: Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 Ohms Resolution . . . . . . . . . . . . . . . . . . . . . . . . . .0.01 Ohms (1%) Max open circuit voltage . . . . . . . . . . . . . . . . . . . . . . . .4.2V Short circuit current . . . . . . . . . . . . . . . .> 0mA @ 2 Ohms
(or am I misunderstanding this spec)
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Bob Eager
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wrote:

No - I think Stefak missed that bit
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D'oh! I certainly did miss that - I'd say you've hit on an excellent cheapie; not a day-in day-out commissioning tool, but a non-ludicrously priced conscientious DIY'ers tool. Nice!
Stefek
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Trouble is, don't such things have to have a calibration certificate to pass regs? And getting a one off checked would likely cost more than buying a commercial version. Unless self certification is allowed...
--
He who laughs last, thinks slowest.

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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I expect they do. It's all about why we're wanting to "pass regs". If it's to get a bit of paper to keep the H&S mafia or the buyer's solicitor off our backs, a test cert for the whole installation from someone who does the job for a living and has paid the right baksheesh, I mean trade association membership fee, is what you need.
If, however, you're wanting to be regs-conformant so that the work you perform is safe to your own satisfaction and so that you can with a clear conscience assert that your d-i-y work is at least as competent as that normally done by a practising professional, while still keeping your spend on use-once-a-year test gear down to sensible proportions, then knocking up something with which to confirm you didn't fall victim to a short bout of narcolepsy while thinking you'd tightened up one of the screws in your new sockets is an eminently reasonabubble use of resources...
Stefek
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Agreed. In The Good Old Days, Maplin would have had a kit for one. I've got a few bits of Maplin kit test gear I still use.
An alternative, of course, is secondhand from Ebay.
--
*Dance like nobody's watching.

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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On Mon, 3 Nov 2003 15:01:24 -0000, "David W.E. Roberts"

The new regs to come into force from April advise that any work undertaken in either a kitchen or bathroom is subject to the regs, and thus a certificate should be issued after testing has taken place.

You most likely won't have much choice in the matter. The problem is going to be be finding a qualified sparky after next April. They look to me as though their diaries are going to be brimming, and an inescapable consequence of this is that their rates will be high.
This all feeds through on dear old Gordons inflation index in due course, but why should he care? By the time the crap hits the fan he'll be out of the chancellors job and some other wally will have to pick it up.
PoP
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Hello Dave,
I recently added a new ring crircuit for my kitchen and tested it with one of these:
http://www.screwfix.com/app/sfd/cat/pro.jsp?id 350
I am quite staisfied with this minimal testing and sleep easy at nights. When I come to sell my house I plan to deny doing any work on it at all.
John

my
new
a
the
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That looks scarily like my trusty rusty multimeter.
More sophisticated than a wet thumb and a nose for the smell of burning insulation :-)
Cheers Dave R
P.S. there is a scary lack of demand for the lynching of top posters - has the newsgroup gone soft?
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On Tue, 4 Nov 2003 21:59:02 UTC, "David W.E. Roberts"
I've got one of those!
But I've also ordered the insulation/continuity tester from TLC - let's see what it's like.

No, we just send the hitmen round these days...!
--
Bob Eager
rde at tavi.co.uk
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