Do i need to rewire or upgrade consumer unit for EICR??

[ebee]

Can I just mention? - I have actually witnessed a bathroom fan timed overun perm L taken from a socket circuit “fused” on the ring final via a 32A MCB no local isolator of any kind of you working on the fan. Therefore I considered it was probably originally a fan that worked only along with the light (fair enough - would not worry me) but then when changed to timed overun it needed a perm L so the nearest handy socket was used. Ahhhh. Thing is it had only recently had “PIR” as we used to call them back then (and it was a residential home so the LA wanted the PIR) this feature was never mentioned on the PIR but a few non faults were coded LOL . The mind boggles

 

[JohnW2]

Can I just mention? - I have actually witnessed a bathroom fan timed overun perm L taken from a socket circuit “fused” on the ring final via a 32A MCB no local isolator of any kind of you working on the fan. Therefore I considered it was probably originally a fan that worked only along with the light ...

OK, that's another way in which there could be a 'borrow' from another circuit.

However, I'm not sure that Simon's/flameport's 'IR measurement' method would detect such a situation, would it? - since, with thee circuits (hence timer's electronics) de-energised (for the test), there probably wouldn't be a path between the L's of the two circuits,would there?

...and, anyway, of course, now that plugwash and yourself have introduced the possibility of 'borrowing' from circuits other than lighting ones, any attempts at using the 'IR measurement' approaches would have to look at IR between the lighting circuit and all other possibly 'involved' circuits.

Kind Regards, John

 

[Murdochcat]

A borrowed neutral can be from any other circuit ...............

 

[JohnW2]

A borrowed neutral can be from any other circuit ...............

It can, indeed, as can 'borrowed lines'.

However, as I was taught many decades ago, "common things are common" - and, in the great majority of cases, borrowed neutrals (or lines) involve two lighting circuits.

If one took "can bee from any other circuit" to heart, then to 'test for borrowed neutrals/lines' (usually prior to installing RCDs for the first time) would involve disconnecting every circuit at the CU, which would be a tedious and time-consuming pain. If it were me, I would probably just look at the lighting circuits and then install thee RCD(s), delaying any further investigation unless/until I found that there were RCD trips.

 

[ebee]

No John, I check them all if doing a conversion whether from no RCD or Dual RCD to Dual RCDs or RCBOs or just on an EICR, I have found them a few times and they can lurk ready to bite someone

 

[JohnW2]

No John, I check them all if doing a conversion whether from no RCD or Dual RCD to Dual RCDs or RCBOs or just on an EICR, I have found them a few times and they can lurk ready to bite someone

Interesting, but do you really routinely 'check' (I presume you probably mean by IR measurement?) for possible 'borrowing between any two circuits? To check between every pair of circuits in a CU of, say, 8 circuits, would be 28 IR tests

Although almost nothing is 'impossible',I would imagine it extremely unusual that there would be a 'borrowed neutral (or line')' from, say, shower,cooker or immersion circuits, wouldn't it?

Kind Regards, John

 

[ebee]

Well no I cannot claim that I have always done it but experience has taught me it does happen and more to the point when I see some things it start to gives me a feeling that some things are more likely to actually have happened. |Some folk think it`s ESP or something but no, it`s just experience telling you to think "Hmm, I wonder if ...." and sometimes you find a yes. Comes in all walks of life in all ways, experience can help with that (not quite as good as hindsight though).
And you do not always need to do the IR test to find out about borrowed Lives (including N) but a few switches on/off combos can be a bit revealing sometimes before you get to IRs and Continuity - Disconnect a L by flicking a breaker/removing a fuse against breaking a N connection on a circuit and sometimes something stops working in both cases and you think "Hah!" .

I did one in a large factory, the offices, several circuits over two consumer unit boards, a certain circuit powered down when either "Main Switch" was off, dead giveaway a L from one CU and an N from the other.

 

[Murdochcat]

Another thread completely ruined ............

 

[ebee]

Another thread completely ruined ............

I think that most comments are related to the OPs original question, so how ruined?

 

[JohnW2]

Well no I cannot claim that I have always done it but experience has taught me it does happen and more to the point when I see some things it start to gives me a feeling that some things are more likely to actually have happened.

That's fair enough, an where 'experience' is of considerable value. I imagine you will probably agree that 'borrowing' is far more likely to occur between two lighting circuits than involving a non-lighting circuit, but if your experience/'bone feelings'/'ESP' tells you that in a particular situation, it's reasonably possible that some non-lighting circuit may be involved, then it makes sense to investigate that specific possibility.

And you do not always need to do the IR test to find out about borrowed Lives (including N) but a few switches on/off combos can be a bit revealing sometimes before you get to IRs and Continuity -

Indeed - as I said, I think it always can be done without any 'measuring' - by flicking off switches' (for 'borrowed L's) or by disconnecting N's at CU (for borrowed N's) - and then seeing what 'stops working'.

My personal inclination would probably be to test for 'linkages' to the probable (other lighting circuits), and also any other circuits which I suspected (in the situation involved) might "reasonably possibly" be involved, but to wait and see if there were any RCD trips before 'routinely'investigating any other circuits.

Kind Regards, John

 

[JohnW2]

Another thread completely ruined ............

Quite so - and, ironically, there are some people who seem to have nothing better to do than to post countless messages which say nothing other than moans about that chatting. .... It's probably at its worst when, as here, the moaning is very largely directed at one person. In forums where I have 'powers', someone who persisted (after warnings) with such 'bullying'/'victimisation' would be thrown out

 

[Risteard]

OK, that's another way in which there could be a 'borrow' from another circuit.

However, I'm not sure that Simon's/flameport's 'IR measurement' method would detect such a situation, would it? - since, with thee circuits (hence timer's electronics) de-energised (for the test), there probably wouldn't be a path between the L's of the two circuits,would there?

...and, anyway, of course, now that plugwash and yourself have introduced the possibility of 'borrowing' from circuits other than lighting ones, any attempts at using the 'IR measurement' approaches would have to look at IR between the lighting circuit and all other possibly 'involved' circuits.

Kind Regards, John

The south of Ireland has an additional test to the IEC ones - "erroneous connections between phase conductors".

 

[ebee]

We were taught on the courses the testing of IR between phases and Ph to N & Ph to E . I always did the "longhand way". P1 to all of the others individually, then P2 to them all individually, then P3 blah blah, then N to E last all with E conductor linked to system E if possible but if not then repeat the tests to that E this time.
There is a "short cut" way that does P1 to all of the rest, then P2 to everything else (but not P1) etc etc etc.

I could list all of the tests indivually but that would make me out to be more boring than I am already . I don`t want Murder Chat on my back.

 

[JohnW2]

The south of Ireland has an additional test to the IEC ones - "erroneous connections between phase conductors".

Interesting, but what exactly does that mean ? Particularly given that the great majority of domestic installations will be single-phase, Does it mean testing between the line conductor or one circuit and the line conductor of all other circuits, or what?

However, in line with what I wrote i the post you have quoted, I'm not sure what test would be able to detect a 'permanent live' for a timer fan that had been 'borrowed' from some other circuit. Am I missing something?

 

[SimonH2]

The electronics in a timer fan would conduct when you apply an IR test voltage - you'd need to use 250V rather than 500V. Between L&N would attempt to power up the timer, between SL and N would create a path through the electronics, as would SL to L.
It's worth testing with both polarities in case there's any diodes/half wave rectifiers in the circuit.
On that last bit, the RCBOs in my rentals test open one polarity, and 65k the other - testing L+N to E. So if I do a whole installation IR test, it fails one polarity and passes (apart from when the outside light was full if water) the other. I have to use my old Megger so I can hold the button down, as the MFT doesn't allow time for the capacitance in the system to charge.