You are right Mike that should be mA not ms in the first paragraph, typical first draft I am afraid. I didn't mention another interesting thing either, and that is that switching the DC on, or resetting the RCD with it on also usually causes another trip, as the current edge obviously causes an inbalance and fires the mechanism. I need to find some other makes of RCD, I have never taken one of this type apart although have used a lot, and have found them particularly reliable. As far as the PSU goes, as there is no load and I put the PSU in the neutral connection there is also no mains voltage difference. The Megger obviously applies the live to earth to get the fault current, and so there is no great danger. Also the PSU is pretty robust anyway, with some capacitance across the outputs, so I don't expect trouble. The only problem I have had with one of these was due to battery charging for long periods at maximum output, the output current sense resistor changed value upwards making the meter reading and current limit rather unsatisfactory (and only 6A too into a 100AH battery so connected a long time). These RCDs are comparatively cheap and from China (isn't everything) and may be from the same factory as some other makes, they are a massive player in the market.


Looking at the results it appears that this type would be fine in a car charging point, there is not a DC problem at 20mA, and they are more than fast enough to give excellent protection although supposedly "only" to 61008-1.

You are right Mike that should be mA not ms in the first paragraph, typical first draft I am afraid. I didn't mention another interesting thing either, and that is that switching the DC on, or resetting the RCD with it on also usually causes another trip, as the current edge obviously causes an inbalance and fires the mechanism. I need to find some other makes of RCD, I have never taken one of this type apart although have used a lot, and have found them particularly reliable. As far as the PSU goes, as there is no load and I put the PSU in the neutral connection there is also no mains voltage difference. The Megger obviously applies the live to earth to get the fault current, and so there is no great danger. Also the PSU is pretty robust anyway, with some capacitance across the outputs, so I don't expect trouble. The only problem I have had with one of these was due to battery charging for long periods at maximum output, the output current sense resistor changed value upwards making the meter reading and current limit rather unsatisfactory (and only 6A too into a 100AH battery so connected a long time). These RCDs are comparatively cheap and from China (isn't everything) and may be from the same factory as some other makes, they are a massive player in the market.


Looking at the results it appears that this type would be fine in a car charging point, there is not a DC problem at 20mA, and they are more than fast enough to give excellent protection although supposedly "only" to 61008-1.