Discuss best practice continuity in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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The thing is with the 2391, they are so pedantic, both with the written and the practical, it is better not to deviate in any way if you want to pass.

@ To the OP, so did they fail you because of this ?, if you don't mind me asking.
 
Nah no fail, not sure if you can fail it? The bloke walked off and left me to it!

It was only when he was looking over the write up and questioned the no R1R2 etc etc

I asked the question for real life purposes not the exam, I know you have to do what they want to see unfortunately, but the assessor was leading me to believe it should be done on site as well, and that R1,Rn and R2 was somehow inferior, which is why I posted originally.
 
Just to clarify, which course are you doing ?, because they can and do fail candidates on the 2391.

I asked the question for real life purposes not the exam


I don't really see the need to do the R1+R2 as seperate measurements in real life either for all of the reasons already said, mainly because you cover 3 items with one test, and quicker is better, as well as more convenient.
But I don't actually see what is wrong with measuring them seperately and adding the results together either, other than you will have more testing steps to do.

In fact GN3 states other testing methods are not precluded, so long as the same end results are obtained.

However on courses it is better to just do it by the book as we have already said, and not 'rock the boat' so to speak.
 
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Its the EAL diploma testing and inspection, equivalent to C&G 2391 so I was led to believe, they just use EAL as the certification body. Got my written test paper on the 26th.

Yeah don't get me wrong I wasn't sat there arguing my point with him, I saved that for here lol I just questioned the logic as I was more interested in making sure I hadn't missed something obvious regarding the benefit of R1R2.

As i've said, in a real world scenario where the cable length was longer than my test leads, i'd combine as it makes sense, just effectively using the line conductor as a wander lead whilst also checking polarity and R1 continuity at the same time, but if it were a situation like the board where you could reach with the leads end to end, I don't see why you would want to disconnect conductors etc when it could be carried out without having too.
 
I think testing r1+r2 is by far the more efficient method than testing separately, as has already been stated. However you appear to have an excellent understanding of the requirement for the test so I'd be very surprised if on this practical the assessor would mark you down for this.
In real life the benefits of the combined test would provide more results in one step, although the specific test result would be the same
 
Another query I have is whats a calculated r1 r2 reading?

Are you measuring the length of the circuit then using the values given in regs for the resistance of said cable to achieve this?

You could calculate the r1+r2 in this way for checking purposes. Rarely used though as it's hard to know exactly how long your circuit is unless measured out during installation.
 
Actually the table for resistance of copper conductors can give a reasonably accurate measurement of length of Cable and r1+r2, but not the first choice method as per previous posts
 
So if you pass this exam i hope that you would get a City & guilds 2391 certificate,would the eal have 2391 written on it,only saying this as agency donks for instance only know certain quals i.e 2391,2382 etc.
 
I'm relatively new to inspection and testing but not to installation. Its a hard road but an interesting one and the forum does help. I'm confident with my inspection and testing procedures and know the tester inside out as it were. I often get perplexed by results even when they are well within tolerance/guidelines/tables etc, particularly when the measured values don't mirror the calculated/expected values. Some would say why care but I'm a bugger for needing to understand why. Most dwellings I have 'I & T'd' during installation and upon completion give Ze readings in the region of 0.12 to 0.17. On my last lighting install the highest measured R1+R2 was 1.79 (landing light fitting) however the Zs taken at this lighting point was 1.09. This gives me a calculated value of 1.91 versus a measured value of 1.09. This is not the first time and I doubt it will be the last but I would be obliged for some theoretical, experienced based explanations to help me understand. Cheers, Rob.
 
Hi Rob
The Zs of any circuit is a combination of the external earth loop impedance and internal earth loop impedance, given by
Zs =Ze+(R1+R2). In a perfect world this calculated Zs should equate to the measured Zs. However in an existing installation there are parallel earth paths which reduce the measured impedance on a live test. These parallel earth paths are not included on a R1+R2 dead test and so result in a slightly higher impedance and therefore an increased overall Zs.
whichever method is used the important point is that the overall Zs is appropriate to the required disconnection times.
Hope this helps
 

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