Who gives a monkeys about RECI? As you said yourself, they recommend this for new build. Existing installations have far too many variabes for this to be good practice.
Rerouting Not Rewiring Cables - Need To Be Signed Off?
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Who gives a monkeys about RECI? As you said yourself, they recommend this for new build. Existing installations have far too many variabes for this to be good practice.
Risteard
Senior Member
How is it a shortcut? It tests everything and is the technically correct way of doing the test, unless you are going to subsequently calculate (1/Rt = 1/R1 + 1/R2 + 1/R3 etc.) - without calculating this you haven't actually established whether the insulation resistance meets the requirements of the Regulations.
I do. I have to keep both RECI and the NICEIC happy. A huge percentage of my work requires RECI membership.
because it's quicker and easier than testing individual ccts if it works. I have used global testing in the past, but I really don't feel it tells you what is really going on with the individual ccts, for example, everything may test out at > 200 M Ohm bar 1 cct which is say 50M Ohm. This would suggest to me that that 1 cct needs closer attention if all the cabling is the same age and maybe developing a fault of some sort / has suffered cable damage from when it was installed such as a back box screw nicking the insualtion.
Global tetsing is a bit like speed limits. A modern car with modern brakes and suspension doing 70 mph on the motorway is a lot safer than an old Morris Minor doing the same speed in the same conditions yet for the purposes of the law both are considered to be driving safely...
BUt goingback to my prevoius point, if we were really expected to calculate global values there would be a box to fill on the test certs - lord knows we have hundreds of boxes to tick and fill in these days!
Global tetsing is a bit like speed limits. A modern car with modern brakes and suspension doing 70 mph on the motorway is a lot safer than an old Morris Minor doing the same speed in the same conditions yet for the purposes of the law both are considered to be driving safely...
BUt goingback to my prevoius point, if we were really expected to calculate global values there would be a box to fill on the test certs - lord knows we have hundreds of boxes to tick and fill in these days!
I was taught at college that the global must be calculated on my L2/L3 & on my 2391, when I did the stint as a 2391 examiner we required the candidates to calculate, but not record, just to confirm the individual readings tied up with the global that they were supposed to do.
W didn't fail them if they did individuals and calculated the global, or if they did individuals and measured the global, both was good, as it taught them the value of doing it.
W didn't fail them if they did individuals and calculated the global, or if they did individuals and measured the global, both was good, as it taught them the value of doing it.
Attached are some screen grabs from 7671 & GN3 (18th).
7671
GN3
IMHO these reinforce Risteards point.
7671
GN3
IMHO these reinforce Risteards point.
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whre did the 20 MOhm figure come from?
Guidance note 3, initial verification, testing.
The 4 screen grabs from GN3 follow on from each other.
but who decided the abstract figure and on what basis? It's a bit like saying any earth rod over 500 Ohms is not good enough or is that 200 Ohms now - I've forgotten!
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You need to work the figures backwards..
AND.. remember the extracts quoted above are from the "INITIAL INSPECTION AND TESTING" of a NEW installation part of GN3...
(e.g. NOT periodic inspection on an old existing installation section..)
so if a new installation Global =20meg.. and you have:-
6 circuits this equals average 120Meg per circuit, Or one low around 30Meg + rest high
8 circuits this equals average 160Meg per circuit, Or one low around 30Meg + rest high
10 circuits this equals average 200Meg per circuit, Or one low around 30Meg + rest high
12 circuits this equals average 240Meg per circuit, Or one low around 30Meg + rest high
14 circuits this equals average 280Meg per circuit, Or one low around 30Meg + rest high
etc..
etc..
etc..
Which..
For a brand new installation IMHO would suggest some dodgy installation work somewhere.?
AFAIK
the 20Meg Global is another rule-of-thumb to indicate if you need to stop and do further investigations.
However...
Personally I still like to know the exact individual circuit figures as well so I can calc OR measure Global!
Guinness
as you said before Specs, given the amount of LED drivers and the like on ccts these days getting good test results is rather difficult even when using LN-E for IR at 250V. I also think we should be doing N-E loop tests.
Anyway, Risteard is clearly correct, although I can't think of a single electrician that does the global calc, apart from Risteard that is :^O . I certainly don't remember ever being taughtt this requirement, but then my training was quite afew years ago. As such, then IMHO a box should be added to test certs reflecting this requirement. It will also alter my Inspection testing going forward - I've always regarded global IR as a short cut, but if that is the ultimate goal, then I shall be using it more going forward.
Anyway, Risteard is clearly correct, although I can't think of a single electrician that does the global calc, apart from Risteard that is :^O . I certainly don't remember ever being taughtt this requirement, but then my training was quite afew years ago. As such, then IMHO a box should be added to test certs reflecting this requirement. It will also alter my Inspection testing going forward - I've always regarded global IR as a short cut, but if that is the ultimate goal, then I shall be using it more going forward.
You mean you don't?
Anyone who works with me does, how else can we confirm the L-N circuit is sound?
My site test sheets have always had this on them.
The global, I always estimate "on paper", because as Specs says it is better to have the individual values.
Also, remember that my quoted abstracts are for IV, not periodic.
For a periodic a global live:earth is fine, that is all lives together to earth, so single phase link L&N then IR to earth, as long as you don't have surge, any filters or similar L or N to earth connections, you'll get a valid reading.
If you get a low value then it's time to break down the circuits & do individual.
I'll mention to the guys on JPEL64 @ Elex Ally Pally if you want a global IR box on the certs...
I would guess that it might be a bit late now for Amd1, but Amd2 will be looked after 1 is out in a couple of years, so it might be able to go in.
I do N-E loops, but many don't as it's not taught or on the test certs
I laughed when I saw this.
Do the JPEL/64 clowns actually think about the ridiculous monster they care continuing to create?
As far as I can tell the 18th edition is scrapping the bottle for changes and some of those included have nothing but "revenue" and "profit" written all over them ..................................
I'm assuming you mean dead tests?
I do the same on all work I do with builders involved!
Yep, dead tests. Nothing more annoying than a neutral fault.
Totally agree
I also do this on existing installations too confirm neutral continuity too ...
Many don't and don't understand the importance of this test
I remember the fist time I encountered a neutral fault, which turned out to be a fault with the DNO supply in the road. I spent hours trying to work out why the hell I was getting the odd readings my test gear was showing me on a small flat I had re-wired completely. I also always do PSCC test, which although it is taught at college, again, many don't do it cos' it's not of the cert.
I know Murdoch, it's crazy. They do have to keep up with IEC 60364, and they have to comply with BS0, it's a shame that they do one and not the other.
When you speak to BSI they insist on impartiality, when you look at the make up of JPEL64... Hmmm...
I have heard rumours that there are documents floating around as to how much the market for AFDD's & surge is going to generate for the suppliers, and these came out before the 18th...
I do the dead tests on R1 & R2 & R1 & Rn, but I also do a ZL-N as well as a Zs test on circuits after they are energised, for the few seconds it takes IMHO it is worthwhile, on both initial verification and periodic testing.
Likewise, whether it be a EICR, a CU change or a new circuit ......... always do it
How can it be impartial when the committees and sub committees have manufacturers on them ..............
I know Murdoch, this is one thing that we won't disagree over!
There are people in the industry who are trying to make a difference but when you are up against a cartel, and big business that goes on behind closed doors it is very difficult to infiltrate and keep your integrity, which is essential if things are to change for the better.
Yup ........... they don't care about anything except keeping themselves busy and in a job ................. now am I referring to JPEL / 64 or Brussels? lol
With the type of business I do the 18th is almost irrelevant ............ so do I need CPS membership and a piece of paper ? and its not as if anyone holds anyone to account for not following the regs ...........
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