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

[HappyHippyDad]

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??

 

[littlespark]

FI.... even if it mean digging the floor up. It’s the only way to be 100% sure.

Other than that, belt in a new rod in an easier place.

 

[Wilko]

Hmmm, if I can’t see it then FI for me.

I have a job underway to add a circuit and the rod results in about 70 Ohms, but it’s been covered by an extension and flooring, I think... Long story short, I have now quoted to add another rod. After confirming the new one works I’ll likely leave both connected at the MET as the invisible one is clearly working as present.

 

[DefyG]

Probably C3 on the basis that there is a acceptable measurement so some sort of electrode!, but improvement recommended (ie a new cable/rod as required for compliance) as currently it cant be visually verified. Personally, I don't see it as 'requiring urgent remedial works'.
C2 if higher than 200ohms
Highlight it and recommend a short interval between next inspection(s) so it can be monitored more frequently! Its probably been like it for years so another 6-12months probably wont make much difference.

 

[HappyHippyDad]

FI.... even if it mean digging the floor up. It’s the only way to be 100% sure.

Other than that, belt in a new rod in an easier place.

Hmmm, if I can’t see it then FI for me.

I have a job underway to add a circuit and the rod results in about 70 Ohms, but it’s been covered by an extension and flooring, I think... Long story short, I have now quoted to add another rod. After confirming the new one works I’ll likely leave both connected at the MET as the invisible one is clearly working as present.

So even though you both disagree on the exact code, you still think it is potentially dangerous. A FI implies that you think it may be a C1 or C2, as if you think it's a C3 you wouldn't FI. Also, if you are going to put in another earth rod (for a customer) you must think it's potentially dangerous as it is, otherwise it could just stay as it is.

It's difficult isn't it!

 

[HappyHippyDad]

Probably C3 on the basis that there is a acceptable measurement so some sort of electrode!, but improvement recommended (ie a new cable/rod as required for compliance) as currently it cant be visually verified. Personally, I don't see it as 'requiring urgent remedial works'.
C2 if higher than 200ohms
Highlight it and recommend a short interval between next inspection(s) so it can be monitored more frequently! Its probably been like it for years so another 6-12months probably wont make much difference.

It may be <200 now, but it could be incredibly unstable as I can't access it to see the termination. Regular checks would be a good idea, but no customer is going to pay you to come out every 6-12 months.

I still think it has to have a new rod, but this can only be guaranteed by giving it a C2.

Again, this is such an important conductor that I don't think we can use terminology like 'probably', it needs to be 'incredibly likely' or 'definitely'. Even though you're probably right ?

 

[Zerax]

As you say... you've already investigated it and can't find it. So FI would seem inappropriate. I'd go with C2 and recommend that, as already mentioned, another rod is put in. Unless of course the owners/builders can dig out whatever is covering it.

 

[loz2754]

FI has in this case proved impracticable, without causing damage to property.
Best practice guide 4 recommends C2 for absence of a reliable and effective means of connection to earth.
The way I see it in this case:
1. You can't prove that it's not absent
2. You can't prove it is reliable and effective from just one measurement, and it's a bit on the high side.
Therefore you don't have a reliable and effective means of earthing, therefore it's a C2.
Therefore install a new earth electrode.

 

[telectrix]

C2 in my mind also. make the buggers pay for stupidity.

 

[loz2754]

severity is high (i.e RCD does not operate and therefore possible death under fault conditions)

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

 

[telectrix]

think he means because the rCD is used for fault protection due to the high Ze/Zs values being too high to trip OCPD.

 

[Risteard]

FI for me is the most appropriate conclusion. New Earth electrode is the most realistic course of action for remediation.

 

[telectrix]

FI for me is the most appropriate conclusion. New Earth electrode is the most realistic course of action for remediation.

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

 

[7029 dave]

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

Oops just kangoed the floor up there's a mat/nest electrode.

 

[telectrix]

wasps nest?