Zs live Testing - does everyone do it?

[Spark123]

I'd suspect it is so that it is done that way to minimise danger arising from the testing, i.e. protective conductors in place before IR testing, polarity dead before energizing, polarity live ensuring correct connection before any live tests, efli and pfc before RCD.
Although it doesn't say you must do R1+R2 it does say you need to carry out the continuity test. This may be the R1+R2 or just the R2 (limited touch voltage).

 

[NotHimAgain]

None of the continuity test actually ask for a reading - just confirmation of continuity (bell & battery )

However, I am trying to extract the sequence and some detail of the test method.

Do you do your R1 + R2 test by putting a link between R1 and R2 at the DB or at various points along the circuit - where is you test instrument and where is your link..

 

[sparkyspike]

I always thought that Ze was a variable figure. So to measure R1+R2 will give you a figure with which to add a Ze reading by enquiry.

I still measure Zs and Ze independently as it is a good check that all is back in place at points of testing, plus loop testing obviously gives you the PEFC and PSSC values.

 

[Spark123]

The schedule of test results asks for it in ohms.
Me, usually pop the phase and earth wires out at the CU and connect them together. Measure L-E at furthest point.

 

[sparkyspike]

None of the continuity test actually ask for a reading - just confirmation of continuity (bell & battery )

However, I am trying to extract the sequence and some detail of the test method.

Do you do your R1 + R2 test by putting a link between R1 and R2 at the DB or at various points along the circuit - where is you test instrument and where is your link..

Link at the DB and tester at points of use.

 

[sparkyspike]

Measure L-E at furthest point.

Not at all points, and record the highest?

 

[NotHimAgain]

Do you do this before the insulation resistance tests or afterwards?

 

[sparkyspike]

Do you do this before the insulation resistance tests or afterwards?

Personally, it's the first test I do. It's easier to measure, say, ring continuity with each circuit one at a time as they go into the CU, before it gets too crowded. Then you can measure IR when all circuits are connected. Usually on a new install, you can measure all IRs in one go with the breakers all up.

 

[GaryMo]

Do you do this before the insulation resistance tests or afterwards?

Before otherwise you would end up repeating an IR test if you found a broken cpc whilst carrying out an R1+R2 or R2 test.

 

[Spark123]

Yeah, at points along the circuit to confirm connection but for the R1 +R2 take the furthest point in the circuit i.e. the last light fitting and the last switch and record the highest result.
Done before IR testing.

 

[NotHimAgain]

Oh it takes a long time to catch a fish on here .

Now draw yourself a little circuit (radial) with, say, three points. Put a neutral to earth short on the first point and reverse the polarity at the second - will your method find it if you just do it when testing protective conductor continuity i.e before you have checked for neutral to earth shorts.

 

[GaryMo]

Oh it takes a long time to catch a fish on here .

Now draw yourself a little circuit (radial) with, say, three points. Put a neutral to earth short on the first point and reverse the polarity at the second - will your method find it if you just do it when testing protective conductor continuity i.e before you have checked for neutral to earth shorts.

Your installs sound like a C&G2391 fault board

 

[Spark123]

You'd find that with the IR test and then repeat the continuity test so would it matter?
You'll hopefully find things like that at initial inspection stage - if you think about it a live and earth reversal is theoretically more likely to be missed during the actual testing on a radial.

 

[NotHimAgain]

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.

 

[GaryMo]

Which is more likely, a broken cpc at a terminal due to being over tightened or your two point fault?