Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This Question of the Day concerns the use of earth loop impedance (ELI) conduit as the circuit protective conductor (CPC), and the testing of it. It is answered by SELECT:
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| Steel conduit as the CPC - but how to test it? |
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Question: I am not an expert tester, but feel that perhaps I am missing something in a project that I am looking at. It concerns a 40-year old property of private flats, having wiring installations to common parts wired via steel conduit, which is used as the CPC.
A recent periodic inspection has returned earth loop impedance results in excess of 200 ohms, which is clearly a fail. However, the conduit installation looks good and I wonder if the test has been properly carried out. There are no records of previous tests to compare.
Could you please advise whether there are any 'unusual' procedures to follow when the CPC is via a conduit system?
Answer: There are no specific procedures other than when using conduit as CPC in new installations - the procedure is to inspect thoroughly, then test continuity using the long lead test (R2) method. When inspecting, ensure that earth tails are installed to the back of accessory boxes - from your description it sounds as though there may be no connection to the means of earthing (if any?). The main earth terminal at the consumer unit should be connected to the incoming earth conductor connected to the means of earthing - check whether means of earthing is provided by the distributor!
To see many more Q & A in Voltimum UK's Experts Area, please click on the link: http://www.voltimum.co.uk/consult.php?universe=consult.index.questions
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