I have a Megger 1741 and I could pay Megger to upgrade it to being a Megger 1741+ presumably with the latest version of the software to give a reasonably accurate test RDC-DD ramp test result, but I still would not know how long it took, only the tripping current at the end of the test period, not the tripping current that actually activated the RDC-DD and started the tripping process.

If I have that right, I’m not sure exactly what I would prove, other than it does trip eventually, not the actual tripping current and not the tripping time.

Megger may state test the RDC-DD, but they are trying to sell you the new all singing, all dancing black tester with red buttons and a colour screen for £1600, if the EVSE manufacturer is telling you to test the RDC-DD then it seems appropriate to do so, even though the Code of Practice is telling you don’t need to, but doing so because you are being told to do so by a tester manufacturer trying to sell you a new expensive tester may not be the best of ideas.

Not that I have anything against Megger, I have five of their testers and one of their EVSE testing adapters, I used my MFT1741 with the Megger testing adapter when I took the C&G exam, but I will never tell anyone they have to buy a new tester when they don’t need to.

Sparkingchip said:

even though the Code of Practice is telling you don’t need to,

Just to be pedantic, the CoP says that BS 7671 doesn't require the test but the manufacturer may specify it. It's a subtle but slight difference, and really aligns with what you are saying yourself - if the manufacturer says do it, definitely consider doing it.

Sparkingchip said:

even though the Code of Practice is telling you don’t need to,

Just to be pedantic, the CoP says that BS 7671 doesn't require the test but the manufacturer may specify it. It's a subtle but slight difference, and really aligns with what you are saying yourself - if the manufacturer says do it, definitely consider doing it.

Thank you

I slipped another post in that I was typing whilst you posted that last comment.

Enjoy your evening. GKenyon seems to  seems to know his stuff. Personally I would test the life out of a publicly accessible product that conducts. You can do the minimum if you like. Legally you will be sound. I need to sleep without worry.

I should hope so, I have the Fifth Edition of the IET EVSE COP of Practice in front of me, have a look at the top of page six.

Also, we were told that on the EVSE installers course I did that legally the Code of Practice has higher legal status than BS7671, so we should always refer to the COP and follow its recommendations rather trying to decide how to do it ourselves based on our own interpretation of the requirements in BS7671.

What is the issue you have? I have stated mine. Did not need the reg’s or a COP. As an engineer you should make sure the work you do os faultless.

I can help ya if you are unsure but you have a responsibility to be electrically safe.

my round next

As an engineer you should make sure the work you do os faultless.

Unfortunately the real world gets in the way of that admiral sentiment. There are many things - in BS 7671 and elsewhere - that are far from ideal, perfect or faultless. Any amount of RCD testing today isn't going to guarantee it'll work as required tomorrow. Shock currents and disconnection times are based on assumptions that probably only hold safe for around 95% of the population - the remaining 5% have trust to luck. Earth faults from distribution and larger final circuits are permitted disconnection times that don't align with shock protection at all. Faults between conductors of different circuits aren't generally considered. Small overloads of long duration are another know problem. L-N voltage operated open-PEN detection devices are known to be fooled by a variety of conditions that can arise from polyphase distribution systems. Errors and failures are to some extent natural and unavoidable.Really the best we can do is to recognise and do our best to control, mitigate or work around the worst of the problems, at an acceptable cost. Generally things are acceptable if they are safer overall than all the alternatives - rather than being free of all possible risk.

   - Andy. 

Hi Andy. 
impedance. We rely on that. I agree with you but live electrical resistance is how fault protection is designed.

impedance. We rely on that. I agree with you but live electrical resistance is how fault protection is designed.

Sorry? I'm not quite following. Yes I know how the calculations are performed, my point is that we only consider impedances related to a single circuit at a time - faults between conductors of different circuits may well have a different range of impedances, and indeed different cross-sectional-areas of conductors to be protected (and possibly different insulation an other factors that provide limits to acceptable temperature rise) but we don't consider them - in many cases it would be impractical to do so - yet the possibility of such faults does exist.

    - Andy.

Give an example