Earth rod 'probably' buried under conservatory, which code?

[Risteard]

but he 's done the FI already, can't find the rod. can't investigate further without a kango.

He mightn't be able to investigate further without a kango, but that doesn't change the fact that without further investigation we don't know for certain whether it's OK or not.

So as I say it's an FI for me - but I would have no issue with someone else putting it as C2 if they prefer. You could put accessibility of the connection as a C2 and the condition of the electrode as an FI if you liked, I suppose.

 

[pc1966]

I wasn't aware an RCD needed a connection to earth to operate correctly.

The RCD might not need an earth rod as such, but it only trips if there is a low enough path to earth. If they are all 30mA instant RCD/RCBO then if it is you form that path then you should not die, but if some are on a 100mA delay incomer then its a different game. But there ought to be a path so if a fault occurs it trips before you tocuh the offending circuit.

Also the system is designed to have an earth. In fact the ESQCR (I think) make a means of earthing mandatory, so the absence of a reliable earth is at least a C2 even with RCD being present.

 

[FatAlan]

See if the DNO will give a PME connection? Appreciate that doesn’t code the existing set up but may be easier that trying to fit a new rod.

 

[GBDamo]

I have just carried out an EICR.

Earthing is TT. A 4mm green/yellow conductor leaves the CU and disappears under the conservatory, I get 158Ω when I do a Ze test.

There is a 10mm that goes to both gas and water. ZS tests are around 40Ω 's on sockets/lights.

I started a similar thread some time ago Unable to find earth rod when doing EICR - https://www.electriciansforums.net/threads/unable-to-find-earth-rod-when-doing-eicr.169576/page-6 which caused lots of discussion and most people erred towards a C3, although NV, LIM and FI were all mentioned, showing that it is a difficult one to code.

I just can't get my head around giving it a C3. It could be classed as the single most important conductor of the whole installation and I can't even get to the termination on the 'possible' earth rod to check it's ok. The termination could be appalling, I could have got 158Ω even if the 4mm conductor was just resting on the earth rod. I was going to say this is highly unlikely, but I have seen some pretty terrible terminations. Also, if the builders didn't have the knowledge to leave it accessible then I doubt they took much care when building around it. Also, builders tend to think earthing/bonding cables are not important and often just chop them off, so again, they could have done anything to it.

When I had to code serious incidents in another profession we looked at 2 influences to get a 'danger' rating.

Likelihood of occurrence and severity if it does occur.

In this case the likelihood is low (i.e termination becomes poor, may not even be an earth rod there, etc etc) but the severity is high (i.e RCD does not operate and therefore possible death under fault conditions)

I think this has to be a C2.

Putting it as an operational LIM is just ignoring the problem. NV is again ignoring the problem. FI..... possibly, but I've already investigated and the rod cannot be found.

I just need to put a new rod in, but with a C3 this may well not happen.

Would you guys still think C3??

You've rationalised it very well, hazard, liklihood and consequence.

The 158Ohms Ze hints at a poor connection, corroded rod, poor ground conditions but ultimately the quality of this rod cannot be verified.

FI will not show anything without invasive works.

NV is a cop out.

C3 will record your findings and coupled with a short retest date may force the owners hand but may likely be ignored.

C2 forces the owner to rectify, and it needs rectifying.

I'd go C2 but its very grey.

My very first earth rod was for the same situation and similar iffy Ze, not absolutely mandated but absolutely necessary.

 

[pc1966]

C2 forces the owner to rectify, and it needs rectifying.

I'd go C2 but its very grey.

Agreed, it should be fixed and adding a new rod should not be too expensive either.

 

[richy3333]

C2 for me.