Bit confused here, IR testing.

[Thommo]

Hi all, this is probably a daft question to most of you.
At training centre I have started dead testing. When I get to the 3 point IR test on a single circuit should I switch off the breaker for that circuit .Hopefully I am correct in removing any lamps on a lighting circuit and turned switches on with all points closed. On a radial or final ring I have closed all points turned sockets on.
I think the procedure may be different when doing a global test, not sure.
Just a bit confused about the circuit breaker as I know it is switched on for continuity of cpc test.
Thanks in advance for any input

 

[telectrix]

Hi all, this is probably a daft question to most of you.
At training centre I have started dead testing. When I get to the 3 point IR test on a single circuit should I switch off the breaker for that circuit .Hopefully I am correct in removing any lamps on a lighting circuit and turned switches on with all points closed. On a radial or final ring I have closed all points turned sockets on.
I think the procedure may be different when doing a global test, not sure.
Just a bit confused about the circuit breaker as I know it is switched on for continuity of cpc test.
Thanks in advance for any input

dead testing is what it says. all dead tests (continuity,polarity, and IR) are carried oit with the circuit/s isolated from supply. on new installations, these tests are done even before the circuits are connected or the CU powered up. don't confuse continuity with loop impedance. the latter is a "live" test.

 

[Thommo]

dead testing is what it says. all dead tests (continuity,polarity, and IR) are carried oit with the circuit/s isolated from supply. on new installations, these tests are done even before the circuits are connected or the CU powered up. don't confuse continuity with loop impedance. the latter is a "live" test.

Thanks telectrix,
Here’s why I am a bit confused.
Here’s a page from my notes I have been given. I have underlined the reason I am confused.

 

[ipf]

You can test circuits for IR individually, or globally. Globally with the breakers on, in order to link them together......more than one circuit, one test, as in many EICR's. Whichever, supply to the breakers must be isolated. It's a dead test.

 

[Thommo]

You can test circuits for IR individually, or globally. Globally with the breakers on, linking them together......all one test, as in many EICR's. Whichever, supply to the breakers must be isolated. It's a dead test.

So the answer contradicts my notes. And confirms the way I have been doing it this week, with circuit breaker in the off position

 

[ipf]

No, either way. With IR you're checking for clearance. If everything is 'clear' from each other with a global test, it's OK. If not, you have to split the circuits and test individually to find which is faulty.
With continuity, you can link the breakers, switched on, to earth. Then test at the end of circuit for continuity. If RFC's are involved, each circuit has to be done individually.
Whichever ways, the power is OFF.

 

[Thommo]

No, either way. With IR you're checking for clearance. If everything is 'clear' from each other with a global test, it's OK. If not, you have to split the circuits and test individually to find which is faulty.
With continuity, you can link the breakers, switched on, to earth. Then test at the end of circuit for continuity. If RFC's are involved, each circuit has to be done individually.
Whichever ways, the power is OFF.

Thanks ipf clarity . So I haven’t been doing it wrong then.

 

[ipf]

Thanks ipf clarity . So I haven’t been doing it wrong then.

It's the same IR test, one circuit or multiple at once. Just think about it.

 

[Thommo]

It's the same IR test, one circuit or multiple at once. Just think about it.

I have thought about it mate, probably too much. Just got a bit confused when I read that note.

 

[Strima]

Thanks telectrix,
Here’s why I am a bit confused.
Here’s a page from my notes I have been given. I have underlined the reason I am confused.

You might want to challenge your tutor on that as it potentially dangerous to carry out IR testing on live circuits.

 

[radiohead]

Hi all, this is probably a daft question to most of you.
At training centre I have started dead testing. When I get to the 3 point IR test on a single circuit should I switch off the breaker for that circuit .Hopefully I am correct in removing any lamps on a lighting circuit and turned switches on with all points closed. On a radial or final ring I have closed all points turned sockets on.
I think the procedure may be different when doing a global test, not sure.
Just a bit confused about the circuit breaker as I know it is switched on for continuity of cpc test.
Thanks in advance for any input

I think the fact that you have stated you are testing a single circuit changes things somewhat from your notes. If you are carrying out a global test (as per the notes) then all conductors will be connected and protective devices on, with the DB main switch OFF! Your test will clearly be carried out on the dead part of the DB.
But you have stated you are carrying out a test on a single circuit, which is not what your notes are describing. This should be carried out with the line and neutral conductors of the circuit disconnected from the DB but with the cpc still connected to the earthing system.

 

[ipf]

I have thought about it mate, probably too much. Just got a bit confused when I read that note.

Global. By switching on CB's you're linking all the outgoing lives. All neutrals and earths are already linked. Just test once between all. Test between any L-N-E. If all clear....done, all at once.

 

[Thommo]

You might want to challenge your tutor on that as it potentially dangerous to carry out IR testing on live circuits.

Sorry I may not have explained myself clearly. I am not testing on live circuits.
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I think the fact that you have stated you are testing a single circuit changes things somewhat from your notes. If you are carrying out a global test (as per the notes) then all conductors will be connected and protective devices on, with the DB main switch OFF! Your test will clearly be carried out on the dead part of the DB.
But you have stated you are carrying out a test on a single circuit, which is not what your notes are describing. This should be carried out with the line and neutral conductors of the circuit disconnected from the DB but with the cpc still connected to the earthing system.

Thank you Radiohead, that now makes sense . Obviously you have read my notes more thoroughly than me.

 

[davesparks]

Just a bit confused about the circuit breaker as I know it is switched on for continuity of cpc test.

It isn't always, it depends entirely on how you are doing the test as there are multiple ways to do it.
Assuming you are working on an isolated board then if you are testing continuity of the cpc by the R2 method the circuit breaker has nothing to do with it, also if you are doing R1+R2 with a link at the far end of the circuit the circuit breaker has nothing to do with it.

Obviously if you are testing just one circuit in a live board then you will have the circuit breaker in the open position.

The point is that there is not one fixed way that the test must always be carried out, you need to understand the process, what you are actually measuring and what affects the reading.

 

[Lister1987]

It's one of those how things are taken when instructions aren't (no offense here Thommo) idiot-proof, that is to say a few more words paint a better picture; 'switched off' could mean in any number of places; main isolator (tails), main switch (board), RCD (split load) or MCB. 'Switched off at main switch (to isolate board) with MCB turned ON (to allow for test to run through entirety of circuit); that paints a much better and clearer picture

I can be a right ----hat (yes @telectrix I'm sure you'll quote this as many times as possible, on and out of context?) when it comes to clear instruction, if I complete task and it's not to the unspoken standard whoever set the task then i make sure they know that, am sure I'm not the only one ?