Jason Humphries asks about whether not being able to find a TT system earth rod means that he cannot issue a Minor Works Certificate. His question has been answered by the NICEIC (Theme – Regulations & Legislation):
Question: I can't locate the earth rod for a TT system. The property concerned has had an extension built four years ago and it may be buried with no evidence of the earth cable entering the ground. There is a 16mm earthing conductor in the distribution board (not traceable) along with a traceable 10mm bonding to water and oil.
The earth loop impedence at the MET (with bonding and rod conductor) is 2.4 ohms and Ze is 34 ohms to what I believe is the main earthing conductor when disconnected from the MET.
The work carried out was lighting point changes. Zs, IR and RCD tests have all been carried out with all results being acceptable.
Can I issue a Minor Works Certificate with a relevant code?
Answer: Regulation 131.8 requires that before carrying out any addition or alteration, it is ascertained that the existing installation - including the earthing and bonding arrangements - are adequate for the alteration. At that point you have to confirm why they are adequate. Because the rod is not accessible in this case, this requirement cannot be fully complied with and, therefore, may be an issue.
If in any doubt as to the integrity of the earthing arrangement, it would be advisable to put a new one in that is labelled and accessible for future test, inspection and maintenance.
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