Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This one, about a periodic inspection and test on a large food factory installation, and earth fault loop impedance testing, is answered by SELECT:
There are various 110V CTE socket outlets, which are protected by a distribution board having two-pole 16A MCBs fitted. The distribution board is 110V CTE fed from a local 230/110 10kVA transformer.
Apart from measuring the insulation resistance test, R1+R2 and polarity, is there any requirement for carrying out an earth fault loop impedance test for the correct disconnection time?
Answer: For reduced low voltage systems, Table 41.6 from BS7671:2008 should be used for maximum earth fault loop impedances.
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