2core swa, not earth load end.. TT

Discuss 2core swa, not earth load end.. TT in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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robo83

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Hi,

Been to a job with a 2core swa supplying the garage.. The swa has been glanded inside house to CU. But the other end in the Garage has had the swa run in plastic conduit with no gland on the swa so unable to test r1/r2.

However the garage has its own earth rod. So technically the swa is earthed from the house end, with the garage having its own earth rod.

The garage earthing TT is 37.0ohms, would I note this down as the garage r1/r2 circuit. Accepted with the 1667ohms as rcd?
 
Midwest said:
Did you mean to quote the OP Pete :(
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Not sure what you are getting at Middy, just trying to say to the OP that r1 and r2 are readings for r1 Live and r2 Earth as a single conductors, I thought he was meaning R1+R2 or am I getting tangled up somewhere?
 
Robo83, can you not get a croc clip on the armouring at all at the garage end? Then you could measure r1 + r2 this way? Midwest and pete, if that was possible, is that allowed?
 
jaydub said:
I dont follow...
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You are trying to measure the loop of the L and E conductors correct? Which will give you a resistance reading noted as R1+R2 not r1+r2 a small thing but end to end reading r1 r2 and rn are recorded as RFC readings only, and are end to end readings of the L.N and cpc, get the basics wrong and other things will be wrong as well. Of course if you are insulating the armoring from the garage end why would you try and trying to measure the R1+R2 of the distribution cable.
 
Last edited:
jaydub said:
Robo83, can you not get a croc clip on the armouring at all at the garage end? Then you could measure r1 + r2 this way? Midwest and pete, if that was possible, is that allowed?
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Hum.... Not sure what that would achieve.... Think about what you are testing
 
Vortigern said:
the swa earth is not part of the garge earth so R1/R2 is gonna be between L and the Rod E. If I read you right?
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My thought is the garage supply is a circuit off the main db (house CU) and this would have its own loop impedance from the SWA armour, which is its CPC. Then the sub board (garage CU) and the final circuits are the TT bit (?) .
 
He is trying to verify earth continuity to the armour of the cable which is not accessible as it is contained within pvc conduit to isolate it from the TT, this earth continuity is applicable to the circuit from the house and nothing to do with the TT.
 
Vortigern said:
yeh but is it a circuit or just a piece of cable? Where is the loop hah!
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Well if it ain't a circuit how does current / fault current flow in it? Being creative, I'm thinking it's a >32A distribution circuit with a 5 or 1 sec disc time from 411.3.2.3 or .4 - at least it would be if I'd done it in 10mm :)
 
To the op I don't know the task you are undertaking but the EFLI or R1+R2 for the circuit from the house will be between the line conductor and armour of the cable which has been rendered inaccessible. This is the fault path for said circuit and has nothing to do with the TT arrangement. Whatever you are doing you will have to note the reading as Not Verified with the reasons.
 
westward10 said:
He is trying to verify earth continuity to the armour of the cable which is not accessible as it is contained within pvc conduit to isolate it from the TT, this earth continuity is applicable to the circuit from the house and nothing to do with the TT.
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Spot on.

Appoligise to everyone else for confusion.

Pete, duly noted.

The swa has been stripped back and the 2 cores run inside pvc conduit.

I did a board change after the customer had an EICR report conducted. This wasn't highlighted and only became apparent when I begun testing after the new consumer unit was installed.
 
Thanks,

I have put LIM in the box and noted on the EIC.

They also pulled 2 strands from the other swa (another circuit) and connector blocked it and used as the cpc :/ no idea why they never glanded properly.
 
jaydub said:
Wilko has interpreted what I was getting at lol
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Exactly as Wilko said ,don't know regarding the position of the RCD however you will need loop reading /Ze +(R1+R2) to determine that the protective device for the sub-distribution circuit will operate within the maximum time for example if someone should accidently put a spade into the cable.
 
westward10 said:
To the op I don't know the task you are undertaking but the EFLI or R1+R2 for the circuit from the house will be between the line conductor and armour of the cable which has been rendered inaccessible. This is the fault path for said circuit and has nothing to do with the TT arrangement. Whatever you are doing you will have to note the reading as Not Verified with the reasons.
Click to expand...
Will it have any reference to the choice of OCPD? cant see how as it's not being used as a cpc?
 
Jesus this is over complicated. He cannot verify continuity of the armour because it has been rendered inaccessible.
 
Not that I'm into testing.....Could not the OP measure the TN Zs at incoming SWA cable at garage consumer-unit? Note reading and subject that reading from the Ze reading obtained at the house consumer unit giving R1-R2.
Another way...use Method 2 wandering lead, assuming connection can be made onto the end of the SWA armouring using a probe.
 

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