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EICR TT installation coded C2 by electrician

Gomez Addams

Hi,


Anybody got any thoughts on this situation?

I have had an EICR done on a property. There were no issues reported apart from earthing. 

The electrician measured the rod resistance at 534 ohms. He insists it has to be less than 200, but his preference is less than a 100.
He said the 30ma RCD wouldn't trip at the measured value, so didn't bother to test it. Bizarrely, he said he pressed the test button which, of course, tripped, but he coded it C2 "unsatisfactory".

I had already tested it with my meter. I got 400ohms, a worst case trip time of 9ms, best 6ms and 28ma on the ramp test.

I pointed out the 200ohms is a recommendation not a requirement and asked him to justify his C2, he refused and stated he stands by his findings.

I haven't checked yet if there is an obvious reason for the rod to be high, but it seems to me the requirements of the regulations have been met.


  • 0

    In my world of work albeit a specialised area with its own technical guidance this is what we request no matter what BS7671 may indicate or other resistance values to get RCD tripping times.

    "Where earthing of the installation is provided by a local earth electrode arrangement (see section 9.8.2), the earth resistance of each earth rod, plate or tape has to be separately tested. The measurements are to be recorded for future comparison, together with a means of identifying the individual items. This test of earth electrode resistance is a pre-commissioning test which should be carried out using an earth electrode resistance test instrument prior to the installation being energised. An earth fault loop impedance test instrument, which requires a source of supply to be available to the installation, is not appropriate for this test. The earth electrode resistance of an individual earth rod, plate or tape at a filling station in the UK should normally not exceed 100 Ohms. If the value does exceed 100 Ohms it may be unstable. The cause of the high reading should be investigated and rectified (e.g. a better electrode may be required). In any event the product (multiple): RA x RCD rated residual (tripping) current, (I∆n), in amperes should not in any circumstances exceed 25, where RA is the aggregate earth electrode arrangement resistance. RA should not exceed 20 Ohms. (Note: Where lightning protection is installed, the value should not exceed 10 Ohms). A lower value may be required, depending on the rated residual (tripping) current of the RCD selected."

    Records also need to be kept for the life of the installation so that any sudden or gradual degredation can be monitored and acted upon, so if a Electrode reading has been say at 7 Ohms every year for ten years then suddenly goes to 98 Ohms then something has happened that needs further investigation especially if ground conditions wet/dry/frozen are also recorded, so a competant inspector would act upon that review of test results. Only having the one set of results may not show that degredation.

    So Gomez,

    You indicated the ttest electrician recorded 534 Ohms, what was the value recorded from the initial installation and testing of that electrode and each subsequent EICR value recorded? or do you just have that one reading?

    GTB 

  • 0 in reply to Gomez Addams
    Gomez Addams said:
    The IET wiring regulations have no force in law. They are not statutory.

    Agreed ... BUT:

    1. BS 7671 is mandated by legislation (Regulation 22 of ESQCR) for the whole installation, if you have generation operating in parallel with the public distribution network (e.g. Solar PV).
    2. BS 7671, as a British Standard, is used as evidence in court for relevant cases involving installations within its scope.
    Gomez Addams said:
    The requirement is it "safe". EICR is not a requirement. It is a possible method.

    OK, but if one uses another method, worth being prepared to defend that position. At the moment, the view that reliance on the RCD without an effective means of earthing is OK goes against all the published guidance  (including BPG4 which you quote - see below).

    Gomez Addams said:
    The question was if the resistance is in spec and the trip times are adequate, where is the potential danger?

    The guidance says there may well be, and I'm sorry if you don't like the fact that I've pointed out that the means of verification prescribed i n BS 7671 hasn't been met for this installation (and provided a credible reason why the electrician didn't carry out the RCD tests themselves).

    Gomez Addams said:
    Best practice guide 4 cites C2 for RCD not tripping. It says nothing about rod resistance above 200 ohms.

    BPG4 actually says C2 for: 'Absence of a reliable and effective means of earthing for the installation.'

    ... it's the first entry under C2

    As discussed, the technical guidance for inspection and testing, and BS 7671 itself, advises earth electrode resistance > 200 Ω may not be stable.

    Apologies if you're offended by my opinion on this topic, but it's sadly not going to change without seeing the installation in question for myself.

  • 0 in reply to Gomez Addams

    That second paragraph is just plain nonsense. In the private rented sector, at least in England, there is a statutory requirement that an installation comply with BS 7671. See here if you do not believe me: https://www.legislation.gov.uk/uksi/2020/312/regulation/3

    What is your evidence that the [earth rod] resistance is "in spec"? As far as I can see, it has not been measured properly.

  • 0 in reply to Chris Pearson

    Rubbish! Others have made far more helpful and useful critical comments.  The question was if the resistance is in spec and the trip times are adequate, where is the potential danger? Read what was written. He didn't do the tests by his own admission. Best practice guide 4 cites C2 for RCD not tripping. It says nothing about rod resistance above 200 ohms.

    Furthermore, have any of you read the government guidance on landlords safety inspections? It's quite clear. The requirement is it "safe". EICR is not a requirement. It is a possible method. Also, compliance with the latest regulations is not a requirement. The IET wiring regulations have no force in law. They are not statutory. The IET is not an arm of government and has no official sanction.

  • 0 in reply to GTB

    I suspect that Gomez wants "us" to validate his opinion. Afraid that isn't going to happen.

  • 0 in reply to Gomez Addams
    Gomez Addams said:
    Ze measured at 0.27. On the report the spark added the rod resistance to the Ze.

    Doesn't make sense if it's TT ... unless it's not TT ... or the "Ze" is to the Neutral, or only part of the installation is TT ?

    Reasoning ... in TT, the earth electrode resistance RA is part of the earth fault loop impedance path Ze ?

    But without seeing the whole report, it's not easy to tell ... the original post was just picking on ADS for TT and contradicted this "new" information.

  • 0 in reply to Gomez Addams

    Gomez,

    Im not really sure why you came onto the forum and asked for an opinion from other Forum members, many of whom are well known BS7671 Experts and have input into that standard as well as others. All you have done has discounted their advice and indicated in your post above that "I have no doubts they are safe"!! if that indeed is the case why not carry out the EICR's yourself and issue the reports and take the responsibility for what you are reporting? or If you feel that the EICR's have not been carried out correctly then raise a complaint with the local trading Standards Department over the quality of the inspectors EICR Report.

    I have tested thousands of TT earthing systems over my career albeit within a flammable atmosphere installation, where we certainly depend on the three or sometimes four levels of RCD current and time cascading to ensure protection and compliance.

    I would have raised an issue on any single electrode over 200 Ohms in value in fact in my specalised area of work we deliberatly state that any electrode giving a reading above 200 Ohms is likley to be unstable and actually indicate that no single electrode should be above 100 Ohms. So I agree C2 was likley a fair remark albeit FI would have been appropriate, was the ground conditions i.e wet, dry, cold, frozen mentioned when the test was carried out as if this reading was obtained when damp/wet then readings will only get worse as soil drys out.

    Why ask for opinions then disregard and criticise those trying to assist on this forum.

    GTB

  • 0 in reply to Gomez Addams
    Gomez Addams said:
    You picked out it trips on the button.

    Because that makes no odds to testing for BS 7671 conformity, which requires two steps as I said:

    1. Earth electrode test; and
    2. Then, if safe to do so, RCD test.
    Gomez Addams said:
    I also said it trips on RCD tests too, all of them, and in less than half the limit.

    I also said it may be considered unsafe to do that test, if the earth electrode test  (or a loop impedance test) is not satisfactory. The electrician has to abide by the Electricity at Work Regulations whilst at work ... that may or ,may not apply to yourself, and I'm not questioning that.

    As far as BS 7671 is concerned, the electrician may have considered the verification for ADS failed at "step 1" and stopped there (which as I have said, may be difficult to argue with if one has no other knowledge of the installation, as is the situation for myself and other posters here).

    I'm not sure why going round in circles will change anything ... BS 7671 has criteria in Regulation 643.7.1 b), which the electrician obviously considered are not met, and just pointing at "step 2" of the verification in Regulation 643.7.1 b) doesn't change the status of "step 1" of that Regulation (at least in the eyes of the original electrician).

    Gomez Addams said:
    I have no doubts they are safe.

    Whilst I wouldn't want to contradict you, as you have knowledge of the installation, I am discussing the criteria in the Standard we are supposed to be inspecting and testing against?

    Gomez Addams said:
    I didn't know until later when I spoke to my tenant that he had told her "he didn't have the right equipment with him to do all the tests". So what didn't he have? RCD tester?

    Also, the reports say 25% of accessories sampled. Another of my tenants told me, he didn't see the electrician remove any fitting whilst he was there.

    I have zero confidence in anything he has said or reported.

    I'm not sure there's enough to go on here for me to comment further, and of course you'd need to make your own decision on each of these things.

    However, in your original post, you only questioned the RCD test ... you said you believed the criteria are met, but I think on that particular point, the electrician may have been following the criteria as stated in Regulation 643.7.1 for TT systems?

  • 0 in reply to Gomez Addams

    Yes but it is exactly that, a guide. It isn't electrics for dummies. You still need to use judgement and common sense. You said you have 3 other properties in the area with spikes where the readings are acceptable. That to me indicates there may be a problem with the spike.  I would FI it with local knowledge. 

  • 0 in reply to gkenyon

    You picked out it trips on the button. I also said it trips on RCD tests too, all of them, and in less than half the limit.

    I didn't know until later when I spoke to my tenant that he had told her "he didn't have the right equipment with him to do all the tests". So what didn't he have? RCD tester?

    Also, the reports say 25% of accessories sampled. Another of my tenants told me, he didn't see the electrician remove any fitting whilst he was there.

    I have zero confidence in anything he has said or reported. I have been through these properties myself in minute detail. I have no doubts they are safe.

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