Arriving to find the earthing has been cut: what you can and cannot certify
An electrician attends a 1970s weatherboard house to install a new 20 A circuit for a heat pump. Before starting, they do a quick check at the main switchboard and find the main earthing conductor has been disconnected and taped back, the MEN link is present, and the earth electrode at the board is not connected to anything. An earth fault loop impedance test on an existing socket circuit reads 2.9 Ω. The installation has a 30 mA RCD which does not trip when its test button is pressed. The homeowner says the previous owner 'had a mate do the wiring', and there are no certificates among the property documents. The homeowner wants the heat pump installed today and is not interested in 'extra work'.
1. What is the status of this installation, and what must happen before any of the new heat pump work proceeds?
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Status: immediately dangerous.
- With the main earthing conductor disconnected, exposed conductive parts of Class I equipment are no longer connected to the earthing system. A phase-to-frame fault will not operate the protective device; touch voltage on the appliance case will sit near phase potential.
- The 2.9 Ω loop impedance reading on a final socket circuit confirms there is no effective earth return path.
- The RCD failing its test button means the one device that could have provided backup protection is also not functioning.
Actions, in order
- Do not start the new work. Do not energise anything new.
- Make the installation safe: either restore and verify the earthing system and the RCD, or isolate the affected circuits - and if the fault cannot be rectified, the supply should be left isolated and tagged.
- Inform the homeowner verbally and then in writing of the defect, the danger, and what is required.
- Record the test results taken.
Judgement point: this is not a 'note it on the certificate' item. A disconnected main earth on an MEN installation is a danger to life, and the electrician who works around it and energises a new circuit has accepted responsibility for it.
2. Assuming the earthing is repaired and the new circuit is installed correctly, what does your Certificate of Compliance cover, and what must it record about the pre-existing defects?
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Scope of the certificate
- A CoC certifies that the work described on it has been done in accordance with the relevant standards (AS/NZS 3000 and the cited standards), has been tested, and is safe to connect.
- It does not certify the whole installation. The electrician is not signing off the previous owner's mate's work.
But the new circuit depends on the installation earthing system for fault protection. You cannot certify new work as compliant when the protective measure it relies on is defective - so the earthing repair must be completed and tested before the new circuit can be certified.
What must be recorded
- The work actually done, including the remedial earthing work (it is now part of the certified work).
- Test results for the parts of the installation affected by the work, including the main earthing conductor continuity, EFLI, and RCD trip times.
- Any departures from AS/NZS 3000 and why they exist.
- The pre-existing defects found and when the customer was told.
Judgement point: the certificate's scope is limited, but the electrician's liability is not limited to the cable they pulled in. Anything the new work relies on for safety must be verified.
3. The homeowner refuses the earthing repair and wants only the heat pump circuit. What is your position, and how do you protect yourself professionally?
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Position
- The electrician cannot install and energise the new circuit. To do so would be to connect a load to an installation with no effective earth return and no working RCD.
- Decline the work in the form offered; offer it again once the earthing and RCD are rectified.
Steps
- Leave the installation in a safe state - repaired, or isolated and tagged.
- Confirm the advice in writing: defect, test results, risk, required remedy, and that you have declined to proceed.
- Keep copies of test results and correspondence.
- Do not accept a written instruction from the customer that purports to waive the safety requirement - a contract term cannot override the statutory safety obligation.
- If the customer intends to re-energise or have someone else energise the installation in that state, make that clear in your records; consider whether the situation needs to be escalated.
Judgement point: the commercial pressure to 'just do the job' is exactly what the exam is testing. The correct answer is a documented refusal, not a conditional certificate and not an unrecorded verbal warning.