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?
Interesting point, - not one that had come to my attention. Personally I'm of the school of thought that testing the CPC is actually present & continuous , as well as the RCD functions is a good thing, at least with a time/ current limited test (< 30mA for ever, or reduced time with rising currents as per the shock curves.), so "method one" for me. ;-)
However I also appreciate that where an RCD supplies a system with no cpc to provide shock protection - not perhaps in the UK at least officially, but certainly OK in Italy at one point, and very common in Latin America today, then another reliable method to assure RCD function without giving someone a shock from things that are doubtfully earthed is essential. Z method (method 2 ) accomplishes this neatly.
Mike
Interesting point, - not one that had come to my attention. Personally I'm of the school of thought that testing the CPC is actually present & continuous ,
To conduct the test without checking the cpc in the first place can be dangerous ... and GN3 recommends a loop test is done first [as well as the continuity and, if fitted, earth electrode resistance, tests are required by BS 7671 before energization] ... so how many times does a cpc need checking?
It's really a moot point for many 30 mA RCDs, because the fault path for "additional protection" is not necessarily back down the cpc as with fault protection in ADS - the example of the severed lawnmower flex is often used, and in that case there is no cpc.
However I also appreciate that where an RCD supplies a system with no cpc to provide shock protection - not perhaps in the UK at least officially,
Don't forget RCDs can be used in IT systems as well.
Interesting point, - not one that had come to my attention. Personally I'm of the school of thought that testing the CPC is actually present & continuous ,
To conduct the test without checking the cpc in the first place can be dangerous ... and GN3 recommends a loop test is done first [as well as the continuity and, if fitted, earth electrode resistance, tests are required by BS 7671 before energization] ... so how many times does a cpc need checking?
It's really a moot point for many 30 mA RCDs, because the fault path for "additional protection" is not necessarily back down the cpc as with fault protection in ADS - the example of the severed lawnmower flex is often used, and in that case there is no cpc.
However I also appreciate that where an RCD supplies a system with no cpc to provide shock protection - not perhaps in the UK at least officially,
Don't forget RCDs can be used in IT systems as well.
We're about to take you to the IET registration website. Don't worry though, you'll be sent straight back to the community after completing the registration.
Continue to the IET registration site
