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Good evening

I am currently a training to become an electrician. I do hold both initial verification and periodic testing qualifications however this is an issue I have never personally had to deal with and was never mentioned on any of my courses as often seems to be the case.

Basically I am wondering how you would hypothetically go about testing either a ring or radial circuit if you didn't have a seperate cpc but the conduit itself acted as this.

Look forward to hopefully getting a response and some clarity

Regards Harry
 
For a radial circuit you can calculate R2. If you measure the continuity of the line and neutral then divide in half this will give you R1 assuming the line and neutral are of the same length. Then measure R1 + R2 and deduct your first reading which should give you an approximate R2. For a ring final circuit you cannot do an r2 for the cpc as you have no end to end as such but you can use the same principle to to calculate R2 from the farthest point.
 
R2 being the CPC I don't think you should be calculating it.
There is nothing wrong with my suggestion, you are using various measurements and using some calculations to extract R2. Using a wander lead and subtracting the leads resistance is no different as this is also a calculation.
 
There is nothing wrong with my suggestion, you are using various measurements and using some calculations to extract R2. Using a wander lead and subtracting the leads resistance is no different as this is also a calculation.
You should never calculate R1 +R2. Or R2 But you can calculate your ZS. This is what the NIC have told me is acceptable
 
You should never calculate R1 +R2. Or R2 But you can calculate your ZS. This is what the NIC have told me is acceptable
How do you measure R2 with no calculation. Your own method not how the NIC think it should be done.
 
During the design stage it is very much acceptable to calculate R1+R2 and necessary in most of, if not all cases
I’m not talking about the design stage. I’m talking about testing on site. We should be avoiding live testing whenever possible. And doing an R1+R2 test. Then calculate the ZS. Not always possible I know but the NIC I believe are trying to get this pushed forward because people are working live on steps trying to do a ZS and having accidents
 
How do you measure R2 with no calculation. Your own method not how the NIC think it should be done.
What calculation would you need to do to perform an R2 test? You need to Null the wandering lead first if that’s what your referring to?
During the design stage it is very much acceptable to calculate R1+R2 and necessary in most of, if not all cases
also I personally think that a measured R1 +R2 test gives a more true reading than a ZS because a Zs is influenced by potential parallel paths that will lower the reading. And as we know parallel paths can be removed. If this occurred the ZS could potentially raise above the acceptable level for the circuit/ protective Device.
 
What calculation would you need to do to perform an R2 test? You need to Null the wandering lead first if that’s what your referring to?

also I personally think that a measured R1 +R2 test gives a more true reading than a ZS because a Zs is influenced by potential parallel paths that will lower the reading. And as we know parallel paths can be removed. If this occurred the ZS could potentially raise above the acceptable level for the circuit/ protective Device.
Parallel paths will in most cases result in a lower result of zs than the calculation of zs=ze+(R1+R2) rather than a higher value
 

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