What do you consider a sample to mean during an EICR

We can again discuss this forever, but as Lyle says the important bit for assessing general condition is inspection. I see no reason to do sampling at all in a domestic, but this is where a proviso comes, if any significant problems are found I do 100% inspection of every accessible connection. Usually, the CU has numerous connections I consider to be loose when checking all the tightness, and this says one thing, the installer was not careful to tighten properly so every screw is suspect. Almost always they are all looser than the current torques suggested by manufacturers, and the reason is easy to see. The screws on modern accessories are larger than older types, and many of the screws were tightened with a 3mm screwdriver, which has a small handle and cannot be turned very hard, often the ubiquitous "neon". Modern tools have bigger handles and so the screws, which may have suffered some creep or always been loose, can be tightened more. I remove accessory fixing screws with an electric screwdriver which makes the job quite quick so looking in 20 or 30 sockets takes an hour or so unless they are very old patress types that are always loaded with very short wire ends! The light switches and ceiling roses are also done and then while dismantled can have wander lead tests and inspection for lack of CPCs.

At this point, the general condition is fairly obvious, and a realistic set of tests may be applied easily, but there is little point in doing everything as if a new installation. I like to loop test every socket and light (My old 2391 tutor, Tom, loved this), and usually, an insulation value for the whole installation is adequate (only L&N to Earth). Any problems can then be noted, and remember this is not a fault-finding job, it is I&T to decide if continued use is satisfactory.

I will now have a lot of comments of the "what if" kind but think a bit, you have tested the Earthing, fixed any loose connections, seen any install problems that can be accessed, noted any broken accessories, and seen any likely high-temperature bits. You have seen the quality of the installer and got the condition. You may want full ring tests if you have seen modifications or new work, and you will have done RCD tests if any present when you did the loops (perhaps by accident!).

I consider excessive dismantling a serious problem as it is likely to induce faults, and these will probably not show unless you do all the testing again. I find very few installs that are fully satisfactory, I do use a 3 neon test plug to check polarity and neutral at every socket (surprising how many are wired backward) and an MFT with wander lead. My worst hate is undoing painted ceiling roses! I rarely even think about the design in a domestic, they are too small to have Zs troubles, and the loop tester gives a warning anyway.

Thanks to all those who sent poor EICRs to me, the matter is now under serious consideration by the IET, all data gained is anonymous.

David Stone said:

I remove accessory fixing screws with an electric screwdriver which makes the job quite quick so looking in 20 or 30 sockets takes an hour or so

That's fine until you come across the screws with chambled heads; rusted in; or stripped threads, either of the screws themselves or the back boxes.

I agree with all of that. Are you me?

Z.

Not Exactly you zoom, probably old school though!Chris the stuck ones get the full impact driver treatment (either loose or broken) then a tap or a new box. Adequate violence is good. If it won't come apart it fails!

David Stone said:

Usually, the CU has numerous connections I consider to be loose when checking all the tightness, and this says one thing, the installer was not careful to tighten properly so every screw is suspect.

Or it says that terminals with single screws can and do become loose over time for various very valid mechanical reasons - but isn't that a further argument for 100 % inspection?

Other than that pedantic point, I think you have given a very good precis of an approach that is likely to pick up most issues.

David Stone said:

Usually, the CU has numerous connections I consider to be loose when checking all the tightness, and this says one thing, the installer was not careful to tighten properly so every screw is suspect.

Or it says that terminals with single screws can and do become loose over time for various very valid mechanical reasons - but isn't that a further argument for 100 % inspection?

Other than that pedantic point, I think you have given a very good precis of an approach that is likely to pick up most issues.