Discuss RCD tripping in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
I'd been pondering this for a while and had come to the same conclusion... I almost added some vague thoughts along those lines but lacked the confidence.Not necessarily. SPUs will chop the tops off excessive voltage peaks, but as happysteve explains, what tends to trip RCDs during spikes and brownouts is not the voltage itself but the sudden changes in voltage (dV/dt). The high rate of change causes high peak currents to flow through any capacitance to earth such as within interference suppressors, which the RCD detects as leakage (which technically it is.) Clearly if there is a high peak voltage with a high dV/dt, then the SPD might reduce it to the point where it doesn't cause a trip.
The cable dropped down in trunking from the CU, under the floor and up to the freezer to a low level concealed socket behind the fridge/freezer. It was not accessible and unlikely to have any future screws run into it, unless they were a foot long.But did the cable supplying the freezer socket need RCD protection?
As SPDs appear to be looking to be mandatory soon in new installations. Then they look like they will reduce the problem of RCDs tripping on power on-offs, but fully eliminate it.Clearly if there is a high peak voltage with a high dV/dt, then the SPD might reduce it to the point where it doesn't cause a trip.
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