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

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.

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.

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.

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): R_A x RCD rated residual (tripping) current, (I∆n), in amperes should not in any circumstances exceed 25, where R_A is the aggregate earth electrode arrangement resistance. R_A 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