Minor works R1+R2 measurement

[gazdkw82]

I think I may have asked this question a while ago but not sure on what the answer was and it's come up again at our monthly tool box talk.

When doing a Minor works for an additional spurred socket or extra light fitting on a circuit, should the R1+R2 measurement be taken from the protective device or the socket/fitting you have spurred from?

 

[happysteve]

Don't you need to take the board cover off anyway to measure insulation resistance of the altered circuit? Or are you using double pole protective devices?

 

[gazdkw82]

I think it's a necessary part of what we do sometimes. As long as you are working within your RAMS. Sometimes it's necessary to work on or around live parts. Fault finding is a good example.

Nowadays most CU are all IP2X internally so there is practically zero chance of electric shock

 

[Midwest]

There is an element of risk to everything we do I suppose, just ask Prince Philip. It’s how you negate those risks; like he should have someone else drive him to places.

In a normal situation, there is no reason to work live. You would to ask why then, in other circumstances, you are required to work live.

For example, in a domestic environment, I can think of very few examples (if any) requiring working inside an unisolated CU.

 

[telectrix]

agree. it's no use confirming that your new has a correctly installed cpc if it is not continuous back to the CU and hence the MET.

 

[gazdkw82]

Some instances it's completely unavoidable. For example, opening trunking to that enclose numerous circuit wiring. You may isolate the circuit your working on but all the other circuit wiring is live.

I've opened trunking before to be greeted with bare copper ends.

 

[ruston]

Some instances it's completely unavoidable. For example, opening trunking to that enclose numerous circuit wiring. You may isolate the circuit your working on but all the other circuit wiring is live.

I've opened trunking before to be greeted with bare copper ends.

That is very worrying.
I can see that there are going to be many revelations in that workplace that are going to bother your conscience.

 

[johnduffell]

just because it's been mentioned a few times and not corrected - a Zs test does not confirm that the CPC is earthed correctly and can not be relied on.
The simple reason is that the apparent earth may be provided via bonding for example an under sink water heater through a metallic pipe.
Any alterations to the plumbing system can render that useless straight away.

 

[gazdkw82]

I spoke with guardian today. They informed me that R1+R2 must be taken from the point of circuit origin.

I have emailed all higher management/technicians and informed them that this is the standard requirement for testing.

 

[gazdkw82]

Well this is just getting confusing now. It really is a grey area.

Our electrical technician has said the contractors we use onsite have said they have spoken with NICEIC and they have said all they need to do is test the leg they have just installed.

I phoned the NICEIC myself and they said it depends on what work has been done. If we are spurring off the load side of a spur then we just test that little section and make a note on the test sheet.

IV just had an email response from a email I sent to guardian over a week ago.

Below is the response. Contradicts what they told me on the phone.

 

[Deleted member 26818]

Welcome to the world of Electrical Regulations.

 

[gazdkw82]

Welcome to the world of Electrical Regulations.

Yes. It's highly frustrating. There must be some literature that settles this somewhere.

I don't see how you can be sure the cpc goes back to the MET without an R1+R2 of the entire circuit

 

[Nigel]

Yes. It's highly frustrating. There must be some literature that settles this somewhere.

I don't see how you can be sure the cpc goes back to the MET without an R1+R2 of the entire circuit

It is clear and if it is not a cpc or a R2 unless it is connected to the MET. If it is not it is just a bit of copper in a cable.

 

[gazdkw82]

Yeh. Getting a clear/precise and consistent view from the powers that be is near on impossible.

 

[johnduffell]

I personally think that you basically have to be satisfied that the r1+r2+ze complies with ADS requirements. Enough to sign your name to it on the certificate. in an installation that is well controlled you could demonstrate compliance by using the documentation available from previous dead testing plus your new partial testing using notes on the certificate to explain your route to compliance so that the documentation as a whole represents the situation.
If the installation has had evidence of unprofessional modifications etc then it would not be professional to alter it without a full test.
As with everything in life you have to follow the rules unless there's a reasoned/risk assessed justification not to. If you can do the risk assessment then you can defend it in court

 

[brianmoooore]

How about measuring R2, with a wander lead , between the furthest part of the new circuit and the earth terminal of a socket that is close to the consumer, but definitely on another circuit? R2 value will be high, by the R2 of the socket circuit, but will at least confirm the continuity of the cpc.