Hello, I am dealing with an office refurb and existing installation consisting of about 8 rotary isolators on a ring circuit wired with 2.5mm2 singles and fed by BS88 32Amp fuse. From as builts it appears isolators supposed to serve power poles which appears were never installed, but I would like to reuse the existing circuit to feed new HRU - about 3Amp 1ph supply. Do I need to change the circuit to radial/replace isolators with fused spurs or can I reuse one of the existing isolator? I feel I can't use the isolators but doubt arose in me when my boss said that he thinks using isolators is compliant with BS. Please let me know, thank you :)
that means I need to allow for an RCD protection then as I am using a ring circuit and the rating of the circuit is up to 32 Amp?
You'd only need 30mA RCD protection if your new work is supplying sockets rated 32A or less, outdoor portable equipment (again 32A or less), soft sheathed cables embedded in walls (<50mm deep in insulating walls, any depth in walls with metallic structural parts), passes through certain special locations such as a bathroom or where Zs is too high for the overcurrent protective device to provide ADS within the required time. The circuit rating or topology isn't a factor.
that means I need to allow for an RCD protection then as I am using a ring circuit and the rating of the circuit is up to 32 Amp?
You'd only need 30mA RCD protection if your new work is supplying sockets rated 32A or less, outdoor portable equipment (again 32A or less), soft sheathed cables embedded in walls (<50mm deep in insulating walls, any depth in walls with metallic structural parts), passes through certain special locations such as a bathroom or where Zs is too high for the overcurrent protective device to provide ADS within the required time. The circuit rating or topology isn't a factor.
