2391 Odds and sods

[gap30]

yes mate i was trying to highlight the r1 + r2 part, i got the shock of my life when i read the examiners comments!

 

[gap30]

good luck

 

[La Poste]

Referring back to SWA again there is no mention of special IR tests but GN3 page 34 states:

"Installation incorporating SWA will introduce parallel paths to protective conductors.
In such situations the R1+R2 test will need to be done prior to final fixing"

So there you go, there is no mention of special IR test procedures but R1+R2 is specifically mentioned so I guess you would have to remove the CPC from the board to test R1+R2 if the SWA had been already installed and the armour had been earthed.
It would be easier doing this way than trying to remove the armour earthing if you had a metal clad board.

 

[Deleted member 26818]

Really only applies when the armour is being used as the CPC, same with metal conduit and trunking.

 

[VMan]

Referring back to SWA again there is no mention of special IR tests but GN3 page 34 states:

"Installation incorporating SWA will introduce parallel paths to protective conductors.
In such situations the R1+R2 test will need to be done prior to final fixing"

So there you go, there is no mention of special IR test procedures but R1+R2 is specifically mentioned so I guess you would have to remove the CPC from the board to test R1+R2 if the SWA had been already installed and the armour had been earthed.
It would be easier doing this way than trying to remove the armour earthing if you had a metal clad board.

did you do another test paper?

it will only introduce parallel paths if used a a cpc, if it has separate cpc then it wont introduce parallel path the the separate cpc.

think if the swa is cpc and its connected to metal conduit via gland, then when u measure the armour as cpc its adding the parallel paths, where if its a 3 core cpc, the cpc is not connected to the metal conduit!

i will try draw a pic

 

[gap30]

Referring back to SWA again there is no mention of special IR tests but GN3 page 34 states:

"Installation incorporating SWA will introduce parallel paths to protective conductors.
In such situations the R1+R2 test will need to be done prior to final fixing"

So there you go, there is no mention of special IR test procedures but R1+R2 is specifically mentioned so I guess you would have to remove the CPC from the board to test R1+R2 if the SWA had been already installed and the armour had been earthed.
It would be easier doing this way than trying to remove the armour earthing if you had a metal clad board.

well done mate i was reading up on that last night as well, gn3 giving reference to testing at various stages of the installation to avoid this exact situation

 

[La Poste]

Maybe a special mention in the answer that the armour is not being used as CPC so need to disconnect it.

I mean in reality the armour is separated from the line conductor within by two sets of insulation, one covering the line cable and one covering the line neutral and cpc.
With all that insulation between the armour and the line I can't see how it would affect the results of an IR test and if it did you would want to know about it.
You would want to know if you had bad insulation between the armour and the line.
So it would be best to leave it earthed in my opinion.
But City and Guilds might see it different.
Do you see what i am getting at though, leakage from line inside cable to armour is kind of a parallel path because the armour is also earthed at the DB same as the CPC

 

[Deleted member 26818]

You wouldn't disconnect if it wasn't being used as a CPC.

 

[VMan]

sorry its small and crap it was rushed, (and colours are wrong)
so the top image uses armour as cpc, you see when you do r1+r2 it will include the bonding to my fabulous pipe and back to the met, a parallel path.

the bottom image you can do the r1+r2 with the cores it will not include the armour just the cpc core and line core

make sense? hopefully there wont be a question on this!

 

[gap30]

i have only ever once tested well insulation on armour and that was a fault on an underground swa in a duct for street lighting - turns out the brown was damaged so i used black and grey for line and neutral (identification of conductors of course) and the armour as earth, made brown safe - lovely thought i was gonna be there all day lol