EICR - C2 - circuits 1 and 2 low insulation resistance reading

[flameport]

what we're saying is that it's a right old rigmarole to do any fault-finding

Fault finding can take a long time, however in this case - what faults? Test results do not indicate any faults.

 

[JohnW2]

Fault finding can take a long time, however in this case - what faults? Test results do not indicate any faults.

To be fair, we don't know that for sure - it could just be stupid recording on the form of something which really is a fault - i.e,. "<1,000" might actually mean 0.5 MΩ.

As I've just written, and most other's have implied, we need to know the actual result of the measurements - I cannot believe that any meter gave a result of "<1,000"

Kind Regards, John

 

[dpm_dpmartin]

I am going to ask him.

There appears to be a HUGE disconnect here, but it might be my layman understanding. My Electrician appears to have marked some circuits with C2 because they measured at something less than 1,000MΩ... we don't know what yet... obviously there's a range of 0MΩ up to 999MΩ I guess.

But the comment from JohnW2 says they could be OK as "low as 1 MΩ without necessarily attracting any code, let alone a C2"... if they were, for example, 150MΩ and 666MΩ I guess we could say the C2s are marked incorrectly on this EICR?

But if they're <1MΩ then it's a problem and I do need to find out if he (or anyone) will take on the remedial work if I don't want to have the Tenant leave the property?

 

[dpm_dpmartin]

If that is the case it makes me wonder why he marked <1,000MΩ... as though it was some kind of boundary measurement that was important to the C2 rating. Why not <1MΩ?

 

[JohnW2]

There appears to be a HUGE disconnect here, but it might be my layman understanding. My Electrician appears to have marked some circuits with C2 because they measured at something less than 1,000MΩ... we don't know what yet... obviously there's a range of 0MΩ up to 999MΩ I guess. .... But the comment from JohnW2 says they could be OK as "low as 1 MΩ without necessarily attracting any code, let alone a C2"... if they were, for example, 150MΩ and 666MΩ I guess we could say the C2s are marked incorrectly on this EICR?

Quite so.

If that is the case it makes me wonder why he marked <1,000MΩ... as though it was some kind of boundary measurement that was important to the C2 rating. Why not <1MΩ?

Again, quite so - that's a question that only he could answer.

Kind Regards, John

 

[JohnW2]

Arrggghhh - this daft forum software at work, again! ...

 

[flameport]

There appears to be a HUGE disconnect here, but it might be my layman understanding.

Insulation resistance tests the quality of the insulation on the cables/wires, and will often detect other problems such as moisture, dirt or grease at terminals of sockets, switches and other items.

Insulation resistance testing devices measure in megohms.
0 would be a short circuit and an immediate fail. RCDs / MCBs would probably be tripping often if that was the result.
Anything over 1 is theoretically acceptable, but would not normally be acceptable for a single circuit. It might be acceptable for the installation as a whole, with all of the circuits tested together.
For an older installation, values of 10s to low 100s for each circuit would be typical, and entirely acceptable.
For a completely new, just installed, never used installation, values of many 100s would be expected, and in most cases would exceed the range of the test device which is often 500 or 1000. Hence values such as >499 or >999 which indicate the value was greater than the device could measure.

It's also worth mentioning that if the test leads were not connected to anything, you would also get values like >499 as it would just be 'testing' the air between the test leads.

In most situations, the actual values don't make any real difference to anything - results of 20, 50, 100, 400, 800 would all be acceptable. There are other factors such as the length of circuits and the type of wiring installed which can affect the results, but those are not relevant to a domestic EICR.

There are only a few options for your EICR
1 - The test results are correct, but the comments about low IR are wrong, possibly confused with another installation / EICR
2 - The test results are wrong, and there really is low IR - in which case the actual IR test results are needed
3 - The test results and the comments are wrong.

 

[ericmark]

There seems to no way to answer the question as to if it needs a rewire.

If there is a problem with a circuit there are many ways to get around it, one can be simply to disconnect the circuit.

This can be to disconnect part of the circuit.

I had similar problem with my dad, he dug in heels and said I am not living in a building site, you can do what you want when I am gone.

I did a full rewire after his death, but before this I tried, I looked for ways to improve the installation, I felt if I could install RCD protection then I would have reduced the risk.

However fitting a RCD it tripped far too many times, and I knew likely due to rubber insulated cables where rubber was failing. Since it was dads house, I could not over rule what he said.

So you have to get your options, and as it stands the electrician is the only person who can tell you the options as he has given no clues with the paperwork.

However it seems it is all three socket circuits. So clearly all sockets can't be disconnected. But it may be possible to just rewire sockets.

Although to rewire flush causes disruption and would be better to have a cleared house, surface mount could also be done and orignal sockets replaced with blanks, and disconnected at the consumer unit.

I am suspicious that all sockets have a C2, and wonder if some thing fitted to sockets or the sockets them selves, I.e. USB or filtered sockets not been disconnected. Personally I look at 250 volt as well as 500 volt test, as if a surge protection device then the two voltages will give very diffrent reading.

 

[JohnW2]

There seems to no way to answer the question as to if it needs a rewire.

I really think it's very premature to even consider that question. The IR measurements and associated comments currently make no real sense, such that there may well be no problem at all, let alone a need for a 're-wire'.

Kind Regards, John

 

[dpm_dpmartin]

I did ask the Electrician yesterday for a bit more info. and - most importantly - about how I might go about having him hopefully perform non-intrusive remediation if I could not get the property empty... nothing back from him as yet. I know it's only half a day... but prior to this question he was always responding to me within minutes. I am not, yet, worried... I am a little nervous.

So, I took a look at one of the other EICRs he did for me - one that passed with flying colours (well, a single C3) and it looks like <1000 and >1000 is how he records these numbers.... obviously as someone commissioning the EICR all I really care about is the 'Management Summary' he gives you - "pass mate" or "work to do here bud". Is the general consensus here that the EICRs should, ideally, have figures - and especially in a C2 noted situation?

P.S. - all the others are like this, I just scanned one to demonstrate.

 

[BS3036]

I think the point is that if the Resistance exceeds the range of the meter then an exact number is not possible (or needed). I think he is copying what it says on his meter. It is only when there is a real reading that this practice becomes incorrect.

 

[dpm_dpmartin]

Fair comment. I think (without verification from him yet) that it potentially betrays the Electrician thinking something is special about 1000MΩ though... marking results as <1000MΩ and C2 and saying there is a insulation resistance issue that leads to the need for a re-wire... might be all OK (and inarguable)... but the documentation simply doesn't back that up, yes? There should be a number there... a number expected to be <1MΩ?

Please do bear with me if I'm repeating myself. It's hard to discuss something with an authority / expert when you have none yourself.

 

[ericmark]

0.0077 MΩ is 30 mA so clearly not that low or it would be tripping the RCD, and at one point 0.5 MΩ was permitted. So in the main we look at what the likely result is, and what the actually result is and how far one is to the other, so a home with a circuit which we know should be around 50 MΩ is reading 5 MΩ we know there is a fault.

But really we should be looking at where the fault is, and it could well be we have missed some that had been left plugged it.

 

[EFLImpudence]

Fair comment. I think (without verification from him yet) that it potentially betrays the Electrician thinking something is special about 1000MΩ though... marking results as <1000MΩ and C2 and saying there is a insulation resistance issue that leads to the need for a re-wire... might be all OK (and inarguable)... but the documentation simply doesn't back that up, yes? There should be a number there... a number expected to be <1MΩ?

Please do bear with me if I'm repeating myself. It's hard to discuss something with an authority / expert when you have none yourself.

Yes, think of it like a two-digit thermometer in Fahrenheit.

Were the temperature higher than 99° then the device might show >99 (I don't think it would show >100), but any temperature below 99° would show the actual temperature (e.g. 68°). It would never show <99, so he must think that for anything between 0° and 99°, just saying <100 would be all that were required - although of no help whatsoever.

 

[dpm_dpmartin]

I do so hate difficult conversations like this... I feel beholden to him because he did the EICR and many other people are telling me something is not quite right with it, that will be a threat to him (especially coming from a mere customer!) and it doesn't bode well. I understand that, it's Human nature. But his only recommendation is for me to get the property empty and re-wire it... hardly realistic and certainly not desirable for the person living there (I can handle the temporary loss of rent and I can spin it to look at it as being an opportunity to refresh the place, but that doesn't mean I'm wholly supportive - I'm not in the business of making people homeless)... I do not have the option on the table of remedial work at the moment (whether cheap or expensive)... otherwise I'd jump at it (for an easy life).