Testing - ring circuit in metal conduit ???????

[Djjeff99]

Hi all

I am trying to find out the correct way to fully test a ring circuit installed in metal conduit , which uses the conduit as the CPC (earth) .

I do know how to test a 2 core and earth ring circuit correctly , but i am unsure how to carry out the required tests , and what boxes to fill in on the test sheet , when the ring circuit relys on the conduit for its earth .

How do i measure the r2 reading and how do i measure the R1+R2 reading ????

Can anyone please help ?

 

[ColJack]

don't think it's possible to do R1+R2 without disconnecting the conduit from the CU so that both ends are available otherwise it would just read continuity across the box...

you could just use a wandering lead to the furthest point to measure R2

 

[GaryMo]

It's either measure R1+R2 or just R2, in this case, R2 would be the better option.
I would then carry out an earth fault loop impedance test where you find the highest reading for R2.

 

[ColJack]

don't you need a high current tester to test the continuity of conduit? something in the 20A range...
I'm sure one of our lecturers mentioned it..

 

[Adam_151]

don't you need a high current tester to test the continuity of conduit? something in the 20A range...
I'm sure one of our lecturers mentioned it..

I think the old clair test was removed some years ago, probably something to do with the possibly of starting fires if there was a bad joint out of sight and near combustable matterials.... of course a fault could still do that!

And yeah, agree with the others, your end to end on the CPC and your cross connect of phase and CPC is not applicable in this situation, so mark your end to end CPC box "N/A" and for R1+R2, remove both phase wires, but them in the earth bar and go round and record highest resistance you measure between phase and earth at the socket outlets, do Zs in the normal way; take it at every point and record highest

 

[Djjeff99]

Thanks for the responses , and cheers Adam for explaining exactly how to do the tests .