Continuity of CPC

[Bright_Spark]

Hi all

can someone please explain to me why it is essential to verify the continuity og the cpc (R2) before carrying out an impedance test on a socket outlet install.

Many thanks

 

[Mark.W]

Hi all

can someone please explain to me why it is essential to verify the continuity og the cpc (R2) before carrying out an impedance test on a socket outlet install.

Many thanks

Do you know what an impedance test is? Max Earth fault loop impedance is Zs=Ze+R1+R2
You are testing your R1 + R2, if there is no continuity of your CPC you will have an open circuit.

 

[pevvers]

Or the loop tester will try to find something metal to shove it's 25A down....

 

[Mr Mark Sparks]

a loop test will also "jump" a loose connection r1r2 will show this
i did a job that had an r1r2 of 1200ohms but the zs was normal .50 loose cpc at light

 

[zupos40]

Hi all

can someone please explain to me why it is essential to verify the continuity og the cpc (R2) before carrying out an impedance test on a socket outlet install.

Many thanks

As some else has stated the test sends 25A down the CPC (R2) if this is a high resistance or has bad connection 25A is sufficient to cause overheating and arcing damage to cable, GN.3 also state the could be shock potential if the current can not flow through the cpc it may find another path.

Long before Zs testing and EatW etc I was working with a sparks who was asked to test a spiral stair case in a hospital for earth continuity, he used a 50A clair tester (high current low impendance tester) the result was that the current passed down the stair through the support and blow a large piece of plaster off the wall, I myself have since used the clair tester to find intermitt fault in an old metal conduit system and it fixed the problem (but the cable needed wiring) this test is not allowed anymore, more the pity, no fun.

The aim of testing is not to make it worse is it.

 

[ajelec10]

It may have been mentioned but i think that another reason of the r2 test is to confirm the continuity of the cpc because if you only do a loop (ZS)this will also take into account parell earth paths even the fabric of the building can introduce a parell earth path so as said you may get a good reading but the resistance of the cpc may be high
Hope this helps
AJ