I was asked why the change to six months. To be honest, I couldn’t answer with confidence. I did hear that folk might be more inclined to test the RCD at the twice yearly clock change. Can anyone point me to an authoritative explanation?
Note that the metal lid of the CU is often being held up by the other hand whilst the test is performed, which seems bad design to me.
the saving grace is that the RCD self-test does not impress any voltage on the CPC or earthed metalwork over and above that already there. (being a Z-link from live out to neutral in or v/v)
Of course a real RCD tester will pull up the CPC towards live, but the time and the current are limited to safe, if painful, values, should a human being be the main fault path for any reason.
An ELFI (loop) test may involve higher than 'safe' currents for sustained exposure, but I'd hope folk read the handbook and start out small before working up and stop tests if the earth appears disconnected.
The obvious engineering answer would be not to earth the lid and to use insulating hinges, but I suspect on the typical hinge, it sort of makes adventitious contact, but then the fingers probably mostly grip the paint, so the user is not well connected anyway.
I agree it does not sound great, but I suspect that in practice the risk is negligible
Mike.
the saving grace is that the RCD self-test does not impress any voltage on the CPC or earthed metalwork over and above that already there. (being a Z-link from live out to neutral in or v/v)
Of course a real RCD tester will pull up the CPC towards live, but the time and the current are limited to safe, if painful, values, should a human being be the main fault path for any reason.
An ELFI (loop) test may involve higher than 'safe' currents for sustained exposure, but I'd hope folk read the handbook and start out small before working up and stop tests if the earth appears disconnected.
Unless the RCD is tested using the upstream/downstream method, which is the preferred method according to PD IEC/TR 62350, and now recognized in GN3 9th Ed (2022) as RCD test method 2 ... although in this case I can understand why the preference for RCD test method 1 (test to PE) has been recommended for so long in TN and TT systems, as in a given installation Method 2 will require a more diligent approach to risk assessment etc.
the saving grace is that the RCD self-test does not impress any voltage on the CPC or earthed metalwork over and above that already there. (being a Z-link from live out to neutral in or v/v)
Of course a real RCD tester will pull up the CPC towards live, but the time and the current are limited to safe, if painful, values, should a human being be the main fault path for any reason.
An ELFI (loop) test may involve higher than 'safe' currents for sustained exposure, but I'd hope folk read the handbook and start out small before working up and stop tests if the earth appears disconnected.
Unless the RCD is tested using the upstream/downstream method, which is the preferred method according to PD IEC/TR 62350, and now recognized in GN3 9th Ed (2022) as RCD test method 2 ... although in this case I can understand why the preference for RCD test method 1 (test to PE) has been recommended for so long in TN and TT systems, as in a given installation Method 2 will require a more diligent approach to risk assessment etc.
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