R1 R2 - Explanation help

[Munders]

I'm just starting up and need to have a question cleared up as I've asked a few other sparks and can't get an answer. So if anyone can help me out I'd appreciate it. When doing an R1 R2 test I've seen a few videos where they connect the live into the earth bar and then carry out the test at the switch. My question is that doesn't the parallel paths of the other CPC's effect the result. Why are both live and CPC not isolated like on the R1 R2 for a ring test.

 

[buzzlightyear]

you need to get the book on inspection and testing GN NOTE 3.

 

[buzzlightyear]

I'm just starting up and need to have a question cleared up as I've asked a few other sparks and can't get an answer. So if anyone can help me out I'd appreciate it. When doing an R1 R2 test I've seen a few videos where they connect the live into the earth bar and then carry out the test at the switch. My question is that doesn't the parallel paths of the other CPC's effect the result. Why are both live and CPC not isolated like on the R1 R2 for a ring test.

may I ask in what capacity have you done any testing .

 

[Ian1981]

I'm just starting up and need to have a question cleared up as I've asked a few other sparks and can't get an answer. So if anyone can help me out I'd appreciate it. When doing an R1 R2 test I've seen a few videos where they connect the live into the earth bar and then carry out the test at the switch. My question is that doesn't the parallel paths of the other CPC's effect the result. Why are both live and CPC not isolated like on the R1 R2 for a ring test.

All parallel paths should be removed as far as reasonably practicable when testing for initial verification using the R1+R2 continuity of cpc testing method.
The method i use is to remove the cpc from the earth bar and remove the line conductor from its OCPD and temporary join together.

 

[buzzlightyear]

watch .

 

[cprfenom]

There is nothing wrong with linking a fly lead from the earth bar. When you think about it, this will give you a more accurate understanding of what your Zs will be.

 

[Ian1981]

There is nothing wrong with linking a fly lead from the earth bar. When you think about it, this will give you a more accurate understanding of what your Zs will be.

This does not remove parallel paths such as say a bonding conductor connecting to the gas pipe.
If you are testing say a boiler circuit then if you don’t remove parallel paths then you will most likely get a lower reading back through your bonding conductor which may mask the fact your cpc is discontinuous.
Zs testing is done with all parallel paths connected and the installation energised having confirmed that all cpc’s are continuous but we are talking about R1+R2 testing.
This is referenced in GN3.

 

[Flanders]

If its a new install R1 R2 testing would be done before final connection are made at the consumer unit , but durring an eicr it may not be practical to remove the circuit from the consumer unit so it will not be posible to avoid testing a circuit with parellel earth paths, in an ideal world you would have the original eic to cross referance the results , but in the real world you would have more chance off having next weeks lottery results , so you would have to use your experance to determine if the result is satisfactory

 

[Ian1981]

If its a new install R1 R2 testing would be done before final connection are made at the consumer unit , but durring an eicr it may not be practical to remove the circuit from the consumer unit so it will not be posible to avoid testing a circuit with parellel earth paths, in an ideal world you would have the original eic to cross referance the results , but in the real world you would have more chance off having next weeks lottery results , so you would have to use your experance to determine if the result is satisfactory

I wouldn’t bother to do R1+R2 testing on an eicr.
I’d just measure Zs of the circuit.
Use a R2 wander lead and a visual test to confirm exposed conductive parts are connected to the source of earthing

 

[buzzlightyear]

talking about R1+R2 testing.
This is referenced in GN3.

 

[Ian1981]

At ease space ranger

 

[sham]

The testing on a ring circuit is different from radial. There are books that show the live cable of the radial in with the cpc of the same circuit in the the earth bar. A ring main continuity R1 and R2 test requires crossing over 4 cables that is way you cant just stick all four in the earth bar. it will spoil the path of the ring. A live Zs test, on radial, might give an closer reading that matches the calculated R1 R2 reading added with the Ze, if it is connected to the earth bar because they both went through parallel earth paths.