Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This one, about use of an RCBO to protect a domestic lighting circuit, is answered by ABB:
I have read, in the newly published On-Site Guide pg 104 Table 2D, that the minimum protective conductor size recommended for such Type C devices is 1.5/2.5mm, depending on fault level.
Answer: When using RCBOs you should use the guidance relating to RCDs rather than the MCB part when considering protective conductor sizing. This is because it is the RCD that will act on faults to earth at a much lower current (30mA typically) compared with the 60A from the C curve MCB characteristic.
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