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Michael Moore:
Oh thats easy its 7.666Kohm
0.008Megohm
Which is what I alluded to on a Facebook group, and it completely baffled the bafoons there, who were apparently teachers!
Ah, but.. RCDs can validly trip at a residual current of anything between 50% and 100% of IΔn so you should really be looking at keeping leakage below 15mA rather than 30mA for reliability (so perhaps 15.3kΩ rather than 7.6)
There again d.c. insulation tests only indicate simple resistance - in a real system they'll be some capacitive coupling that'll allow some extra residual current to flow too (so perhaps something significantly higher than 15.3kΩ)
Also there'll likely be leakage from appliances which likely won't be part of a fixed wiring test (even if they many appliances will have components switched off - e.g. pumps and motors of washing machines so likely to avoid the test) - so again you might want to add a significant margin on for that too..
- Andy.
Michael Moore:
Oh thats easy its 7.666Kohm
0.008Megohm
Which is what I alluded to on a Facebook group, and it completely baffled the bafoons there, who were apparently teachers!
Ah, but.. RCDs can validly trip at a residual current of anything between 50% and 100% of IΔn so you should really be looking at keeping leakage below 15mA rather than 30mA for reliability (so perhaps 15.3kΩ rather than 7.6)
There again d.c. insulation tests only indicate simple resistance - in a real system they'll be some capacitive coupling that'll allow some extra residual current to flow too (so perhaps something significantly higher than 15.3kΩ)
Also there'll likely be leakage from appliances which likely won't be part of a fixed wiring test (even if they many appliances will have components switched off - e.g. pumps and motors of washing machines so likely to avoid the test) - so again you might want to add a significant margin on for that too..
- Andy.
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