Zs live Testing - does everyone do it?

[NotHimAgain]

The sequence of testing is there for a reason - the R1 + R2 test, carried out in the way some of you have described is flawed.

 

[securespark]

Can I put the cat among the pigeons & comment that if you do EFLI test at all points on a circuit you are automatically testing Zs and verifying R1+R2 (if not measuring it) & polarity, all in one test?

[waits for backlash.... ]

 

[sparkyspike]

Can I put the cat among the pigeons & comment that if you do EFLI test at all points on a circuit you are automatically testing Zs and verifying R1+R2 (if not measuring it) & polarity, all in one test?

[waits for backlash.... ]

With the power on, obviously. Which takes you back to continuity testing!

 

[NotHimAgain]

I don't have a problem with that .

 

[sparkyspike]

I suppose it depends whether you are doing a PIR or an EIC.

 

[ban-all-sheds]

Well gentlemen the R1 + R2 test was an NICEIC invention - it was supposed to provide a continuity test and a dead circuit polarity test all in one - but using your test method it has a fatal flaw.

How did it end up in BS 7671 then?

 

[NotHimAgain]

Is it in BS 7671?

It is in an 'informative' appendix as an alternative to th R2 test for continuity.

The sequence of testing that should be used for initial verification was carefully thought out.

Continuity is before insulation resistance to ensure that all (switched on) parts of the installation receive an insulation resistance test. Insulation resistance is before polarity to ensure that any 'shorts' between conductors are revealed - before any test that relies on circuit conductors to prove circuit arrangement.

The regulations proper do not actually call for a resistance measurement.

Now if you use a bell & battery located at the distribution board and go round with a link - in small installations you can hear the bell toll .

 

[david_uk]

I prefer to do the Zs as well. Using this, I've found several faults recently on rewires due to the crappy design of the cheap roses being specified that I don't believe would have been uncovered by R1+R2 alone.

 

[dingbat]

Sounds like most of you need to go on a course!

 

[ban-all-sheds]

Is it in BS 7671?

It is in an 'informative' appendix as an alternative to th R2 test for continuity.

It's on the schedule of test results.

So yes - it is in there.

It may well be a non-mandatory alternative, but it is in there.

 

[DESL]

To prove BAS point and to clear up any confusion it's all quoted on the reverse of Form 4


NOTES ON SCHEDULE OF TEST RESULTS
*1 Type of supply is ascertained from the distributor or by inspection.
*2 Ze at origin. When the maximum value declared by the distributor is used, the effectiveness of the earth must be confirmed by a test. If measured the main bonding will need to be disconnected for the duration of the test.
*3 Prospective fault current (PFC). The value recorded is the greater of either the short-circuit current or the earth fault current. Preferably determined by enquiry of the distributor.
*4 Short-circuit capacity of the device is noted, see Table 7.2A of the On-Site Guide or Table 2.4 of GN3
The following tests, where relevant, shall be carried out in the following sequence:
Continuity of protective conductors, including main and supplementary bonding Every protective conductor, including main and supplementary bonding conductors, should be tested to verify that it is continuous and correctly connected.
*6 Continuity Where Test Method 1 is used, enter the measured resistance of the line conductor plus the circuit protective conductor (R1+ R2). See 10.3.1 of the On-Site Guide or 2.7.5 of GN3. During the continuity testing (Test Method 1) the following polarity checks are to be carried out: (a) every fuse and single-pole control and protective device is connected in the line conductor only (b) centre-contact bayonet and Edison screw lampholders have outer contact connected to the neutral conductor (c) wiring is correctly connected to socket-outlets and similar accessories. Compliance is to be indicated by a tick in polarity column 11.
(R1 + R2) need not be recorded if R2 is recorded in column 7.
*7 Where Test Method 2 is used, the maximum value of R2 is recorded in column 7. See 10.3.1 of the On-Site Guide or 2.7.5 of GN3.
*8 Continuity of ring final circuit conductors A test shall be made to verify the continuity of each conductor including the protective conductor of every ring final circuit. See 10.3.2 of the On-Site Guide or 2.7.6 of GN3.
*9, *10 Insulation Resistance All voltage sensitive devices to be disconnected or test between live conductors (line and neutral) connected together and earth. The insulation resistance between live conductors is to be inserted in column 9. The minimum insulation resistance values are given in Table 10.1 of the On-Site Guide or Table 2.2 of GN3. See 10.3.3(iv) of the On-Site Guide or 2.7.7 of GN3.
All the preceding tests should be carried out before the installation is energised.
*11 Polarity A satisfactory polarity test may be indicated by a tick in column 11. Only in a Schedule of Test Results associated with a Periodic Inspection Report is it acceptable to record incorrect polarity.
*12 Earth fault loop impedance Zs This may be determined either by direct measurement at the furthest point of a live circuit or by adding (R1 + R2) of column 6 to Ze. Ze is determined by measurement at the origin of the installation or preferably the value declared by the supply company used. Zs = Ze + (R1 + R2). Zs should be less than the values given in Appendix 2 of the On-Site Guide or Appx 2 of GN3.
*13 Functional testing The operation of RCDs (including RCBOs) shall be tested by simulating a fault condition, independent of any test facility in the device. Record operating time in column 13. Effectiveness of the test button must be confirmed. See Section 11 of the On-Site Guide or 2.7.15 and 2.7.18 of GN3.
*14 All switchgear and controlgear assemblies, drives, control and interlocks, etc must be operated to ensure that they are properly mounted, adjusted, and installed. Satisfactory operation is indicated by a tick in column 14.
Earth electrode resistance The earth electrode resistance of TT installations must be measured, and normally an RCD is required. For reliability in service the resistance of any earth electrode should be below 200 Ω. Record the value on Form 1, 2 or 6, as appropriate. See 10.3.5 of the On-Site Guide or 2.7.12 of GN3.

 

[NotHimAgain]

How does that "prove BAS point and to clear up any confusion it's all quoted on the reverse of Form 4 "

That text is not in my copy of BS 7671

All that BS 7671 has is a column for R1 + R2 test results on page 341

The text you quote is from GN3 I believe, is it not. Now what is the status of GN 3.

You see this test started life as a continuity check and someone happened to say it could provide an indication of polarity - NOT an absolute confirmation.

The test could be done with a bell & battery - with the bell at the distribution board. This method removes the flaw.

Now some bright idiot decided that a simple continuity test should really be a low resistance measurement, that MUST be done with a calibrated test instrument or its results would not be valid. This has led to the myth surrounding this test and the flawed method of testing.

Still take no notice of me, I haven't done the 2391 so I can't know what I am talking about can I .

 

[Spark123]

The column in the schedule of test results form asks for R1+R2 and has the ohm sign therefore as far as I can see indication with a tick isn't allowed - it is after the ohmic value.

 

[NotHimAgain]

Appendix 6 is 'informative' rather than 'normative' and as such is not required, it is just guidance. See the note on page 227 of BS 7671 for confirmation.

That said, most would want to follow the guidance.

BS 7671 proper only requires a continuity test, it does not give a test method. It does however, mention a voltage range and short circuit current for the test equipment. Note that it does not specify any requirement to obtain a reading, or to use calibrated instruments. See 612.2.1. So don't throw your bell & battery away just yet .

In fact earlier versions of the test forms used to have a tick box for continuity.

There is a rather cheeky reference to GN 3 at the bottom of page 157, but IMO that should be struck out.

Now I could start a debate on the merits of R1 + R2 testing but it would probably end as an argument so I won't bother.

 

[GaryMo]

Now I could start a debate on the merits of R1 + R2 testing but it would probably end as an argument so I won't bother.

Why not start a new topic? I'd be interested.