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Topic Title: senseless results
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Created On: 28 June 2012 10:02 PM
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 28 June 2012 10:02 PM
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jcm256

Posts: 1606
Joined: 01 April 2006

Guidance note 3, provides detailed information in a descriptive way, and it is recognised recommendations based on BS7671 can be most difficult to write.
But, (after that butter up) the following notes to column numbers in the form 4 (Three-Phase) column 1 (for example) for the 5th circuit, the designation 5L1 5L2 5L3, does it mean insert the 3P circuit on one line or over three lines. Note all three- phase circuits are to a motor or immersion heater etc, and can have variant readings. Why not give an example on form 4 for part of a three-phase installation, of the way it be done. Does it matter No. but it would be nice to follow published guidance.

Column 5, still have not got it, adjustable circuit breakers are more and more used in panels, you could put of course 15/30 but then another line is needed for the adjusted setting.

Column 7, Reference method, is this necessary, who wants to know, could be various methods in a large installation, no space to insert several methods. Tables of tables in BS7671, Table 42A not listed

Column 13, 14, the cell may be ticked if senseless results are recorded. Petty grievance, but what a word to use in technical guidance: meaning:
Not sensible or reasonable: unreasonable, wrong, extreme, absurd, childish, irrational, irresponsible,perverse, hysterical, ridiculous...
or Asleep and unconscious: asleep, unconscious, comatose, out, under, sound asleep, fast asleep,semi-conscious, out cold, out for the count..

Anyone can nit -pick holes in any document, but in general, the guide is delivered with the air of authority, which lends status to some meaningless sentence. As Humpty Dumpty, remarked to Alice.

Regards
jcm
 29 June 2012 08:22 AM
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davezawadi

Posts: 2421
Joined: 26 June 2002

I don't have a copy of the latest GN3 yet (sorry Zs), however you are being a bit difficult.
You seem to be describing a 3 phase circuit with single phase items connected so that the test results vary wildly between phases. (They should be very similar on proper 3 phase circuits otherwise investigation is required as this is not OK). So we do the same as normal put in the worst case figure, and code it as requires improvement unless it needs a 3 phase breaker such as 3 phase lighting with common neutral. You can cite reg 341.1 as a single phase fault on an otherwise 3 phase circuit is unexpected and inconvenient.Settings for adjustable MCCBs are best recorded in a separate sheet in the installation documentation, including why the setting is as it is set (often not obvious!).

-------------------------
David
CEng etc, don't ask, its a result not a question!
 29 June 2012 07:41 PM
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jcm256

Posts: 1606
Joined: 01 April 2006

Yes thanks for the reply. But you can still get (quite common) in Garages, schools etc, the three phase supply derived from three separate fuses or breakers in a distribution board ,Big sub-distribution boards even today are like that. In such a case, I think in this case, the 3P circuits need reported on three separate lines instead of one line as suggested (to pick up maybe one inappropriate fuse for example). The example of the way they would like a 3P circuit reported on, is one line. Example given 5L1, 5L2 and 5L3, assuming that 1,2,3 is the way now to describe the three phases and could only be done if it was 100% test and the tester was supplying a new circuit chart in a Polly-pocket inserted in the distribution board, most time the method of numbering would be site specification. However, of course GN3 is only for guidance and not a mothering document for electricians

Regards
jcm
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