Testing question EIC/minir works

[gazdkw82]

Posted this in the wrong section:

We had our electrical engineer talk to us all later week regarding testing. It was agreed that if you were to install a spur socket for example then you only test the leg you have installed. This strikes me as not correct. I would have thought the entire circuit from the protective device would need to be tested?

Secondly I asked the question about Ze. In most cases we would be on a board way down the chain of boards. How do we obtain a Ze. First answer was that we can get the Ze from previous legends (however most are not available) then I got told we could access the gardian portal, however that's not available to me yet. Then the electrical engineer said the Ze can be measured at the board I'm working on.

I said that is not a Ze but a Zdb. He disagreed and said it was the boards Ze.

I was under the impression a Ze was the supply's earthing resistance. A "ze" on a board down the chain of boards will have numerous parralel paths that are not part of the supply's earthing?

 

[telectrix]

you are correct. a Zs reading at a sub-board is a Zs or a Zdb, it's not a Ze. that is the reading at the origin.

 

[Pete999]

Posted this in the wrong section:

We had our electrical engineer talk to us all later week regarding testing. It was agreed that if you were to install a spur socket for example then you only test the leg you have installed. This strikes me as not correct. I would have thought the entire circuit from the protective device would need to be tested?

Secondly I asked the question about Ze. In most cases we would be on a board way down the chain of boards. How do we obtain a Ze. First answer was that we can get the Ze from previous legends (however most are not available) then I got told we could access the gardian portal, however that's not available to me yet. Then the electrical engineer said the Ze can be measured at the board I'm working on.

I said that is not a Ze but a Zdb. He disagreed and said it was the boards Ze.

I was under the impression a Ze was the supply's earthing resistance. A "ze" on a board down the chain of boards will have numerous parralel paths that are not part of the supply's earthing?

T add a spur, in your case you will need to ensure the circuit you are spurring from, has been wired correctly and is in a safe condition to extend, so in theory you would need to test and inspect that particular circuit.
Some say Zdb would be sufficient, not got my regs book so cannot give you a definitive answer on this one.

 

[gazdkw82]

T add a spur, in your case you will need to ensure the circuit you are spurring from, has been wired correctly and is in a safe condition to extend, so in theory you would need to test and inspect that particular circuit.
Some say Zdb would be sufficient, not got my regs book so cannot give you a definitive answer on this one.[/QUOTE

There must be a definitive description of the testing needed on a spur/alteration etc

 

[Ian1981]

If I’m adding a spur to an existing ring final circuit, then I tend to do the end to end resistance tests between the conductors, an insulation resistance test between all live conductors and earth.
Assuming all test results are satisfactory,
I then would do my figure of 8 testing and include my new added spur in the R1+R2 testing and that is the reading I would put down on my minor works certificate.

 

[gazdkw82]

If I’m adding a spur to an existing ring final circuit, then I tend to do the end to end resistance tests between the conductors, an insulation resistance test between all live conductors and earth.
Assuming all test results are satisfactory,
I then would do my figure of 8 testing and include my new added spur in the R1+R2 testing and that is the reading I would put down on my minor works certificate.

What about if your adding a new light to the end of a circuit?

 

[Ian1981]

What about if your adding a new light to the end of a circuit?

If installing new cables and adding/altering the circuit then,
Check there’s a suitable earth to the circuit, carry out a zs test and insulation resistance tests to make sure the circuit is safe and in a satisfactory condition to add to

 

[gazdkw82]

If installing new cables and adding/altering the circuit then,
Check there’s a suitable earth to the circuit, carry out a zs test and insulation resistance tests to make sure the circuit is safe and in a satisfactory condition to add to

But for the R1+R2, is that the section you have installed or the entire circuit?

 

[Pete999]

But for the R1+R2, is that the section you have installed or the entire circuit?

Deleted wrong info given

 

[gazdkw82]

What's been deleted Pete?

 

[Pete999]

What's been deleted Pete?

I just wasn't sure of the answer that's all. Or to be exact I wasn't sure the answer I gave was the right one.

 

[Ian1981]

But for the R1+R2, is that the section you have installed or the entire circuit?

Well you have said your adding to the end of the circuit so I would test the full circuit and not just the piece of wiring you have installed.
By that I mean take an R1+R2 from your final point you’ve have installed and not testing every single point on the circuit.
By virtue of say taking a zs at the final light to ensure you can add from it , you will have tested it in some form anyway

 

[Richard Burns]

Operationally it is often very hard to obtain a true Ze reading i.e. the EXTERNAL earth fault loop impedance at origin, however in the case of a minor works then only Zs is needed. If you were doing work that required an EIC then Ze would be required to complete the certificate as a possible work around you could state that the DNOs stipulate a maximum value and so you can thereby have obtained a default Ze by enquiry (0.35Ω or 0.8Ω); if the circuit is compliant at those levels then it is OK.
For adding to a circuit you need to ensure the existing installation is suitable for the addition, possibly you can assume that if the circuit is working and your measurements on the finalised circuit are OK then the rest is OK (a bit borderline), however in terms of the test results you are recording that your work is compliant, this may include measurements of parts of the existing circuit (RCD, etc.) but in general you are recording your new work only.

 

[Zdb]

Spurring off of a RFC requires only a minor works certificate. A Ze is not required for this. Your electrician could just test the sub board's Zdb to make sure the earth is sufficient before starting.

As for testing just the newly installed leg, that's a bit of a grey area. I've been told my an NICEIC assessor that you only need to IR test the cable that you've installed. However, I personally test the whole circuit for peace of mind.

 

[gazdkw82]

Spurring off of a RFC requires only a minor works certificate. A Ze is not required for this. Your electrician could just test the sub board's Zdb to make sure the earth is sufficient before starting.

As for testing just the newly installed leg, that's a bit of a grey area. I've been told my an NICEIC assessor that you only need to IR test the cable that you've installed. However, I personally test the whole circuit for peace of mind.

Yeh I understand that, however is this just a preference?

I need something to back me up if I'm to argue the R1+R2 needs to be taken from the protective device and not just the leg you've installed.