First eicr and low iR readings

[Baddegg]

Being new to this game I’ve been waiting a while for the right job to come along and I have now done my first eicr today, small Chinese takeaway 2 circuits (lights and 1 rfc) most cooking appliances are gas, found some interesting stuff like sockets wired from lighting circuit,main bond buried in concrete floor amongst other things...anyway place is not trading at moment and this is due to sale of the business so I managed (I think) to unplug everything it is oldish and I was expecting some low ir results but,...L-N 0.537 N-E 0.076 L-E 0.2....tested my tester on a piece of 10mm cable before and after and they are fine, so other than something being connected I can’t understand why they are so low, rcd tests fine (newish board). Not fussed at filling the report out and stating the findings just my curious nature needs to understand if it’s normal to be that low and suffer no side affects.....
Ps lighting circuit tests at 1.135 L&N to E due to being unable to remove most of the lamps..

 

[Wilko]

and the cpcs on the older (pre 2005) wiring are all blackened/carbonised

Hi - this visual info could explain the low IR and would suggest those cables need to be replaced.

 

[Baddegg]

Blackened?! Any pics? Not familar with that at all. Is the whole place full of oily soot from wok fires or what? That could be a significant factor in low insulation.

Hi - this visual info could explain the low IR and would suggest those cables need to be replaced.

Sorry for the delay chaps.....

You can make out the blackened cpc, it’s the length of what exposed/visible but only on the older cable

 

[westward10]

Looks like it has oxidized. What's it like with the sleeving off.

 

[Baddegg]

Looks like it has oxidized. What's it like with the sleeving off.

Same @westward10, I’m starting to think sections have been removed in the past

 

[westward10]

The terminal screws are the same. This is normally caused by atmospheric conditions. Are the line and neutrals the same.

 

[Baddegg]

Didn’t check them all but the ones in that picture certainly are...

 

[westward10]

Oxidation to copper is like steel rusting, get the right conditions and it will happen.

 

[ruston]

What kind of state is the extractor system and gas interlock in . They are always a bit gungy, and often burned from lack of cleaning.
Ceramic food heaters are another culprit as wrong cables replaced ones that caused the previous problem. That is usually in chippies though.

 

[davesparks]

I'm sure you know that such a low reading is a definite C2, therefore an unsatisfactory outcome on the EICR. Best way to find it is to split ring into sections, and narrow down the location. I recently had a similar result caused by damp affecting several newish sockets and fcus on one particular wall.

Why do you say a low IR is a C2?

 

[bigspark17]

The L-E and N-E readings are quite different which suggests everything could be unplugged. I'd now be looking for damaged wiring or waterlogged sockets etc. Splitting the ring in the middle will help narrow things down.

your there to do an eicr not put right unless instructed to do so.

 

[freddo]

I assumed the OP was at the repair stage.

 

[JBW175]

Why do you say a low IR is a C2?

It says in GN3 that IR readings under 1M Ohm are to be reported as a C2 mate.

 

[JBW175]

I am not your mate, we have never met, please do not refer to me as such

I don’t mind you disagreeing with my post, but here it is in GN3, They also hammer that fact home on the 2391-52.

No ne

 

[westward10]

It is up to the inspector to decide upon a Code and this can involve many factors hence BS7671 does not suggest Code designation. Unless the Guidance Note cites a Regulation it is just that, guidance and not a Regulation.

 

[JBW175]

It is up to the inspector to decide upon a Code and this can involve many factors hence BS7671 does not suggest Code designation. Unless the Guidance Note cites a Regulation it is just that, guidance and not a Regulation.

Fair enough and thanks for the clarification. I was just going off what’s currently being taught and tested on the 2391, as GN3 is the bible on that course; and if we’d have coded a low IR reading as anything other than a C2, we’d have been pulled up massively for it.