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Paultrim123321
Hi, carried out an inspection this week on an installation which consisted of two phase three wire to a small building from an electrical switch room. The supply is wired using 25mm LSF/SWA protected by BS-88 at the sub. At the building the supply is terminated into a 947-3 isolator and then reduced using various tails to smaller DB's and fused isolators. The tails vary between 4mm and 16mm depending on the circuit demand for example the single pole fused isolators are rated at 32A and fed by 4mm tails, the larger 9-Way CU's are fed using 16mm tails. Reading 433.3.1 would you consider this to be satisfactory as the fault protection at the load side of the install is satisfactory for the supply tails? IMHO I am thinking they need to provide local protection at the installation and then size the tails accordingly? This install is approx. 25 years old and no history of overload. I clamped the load whilst carrying out the inspection and the install was only drawing 6A. P.S The two phase supply is another question for later