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 

Megger advert from three years ago, encouraging you to upgrade the tester you already had, if you did then presumably it now needs a software upgrade to reduce the rate of rise on the RCD ramp test to get a reasonable test result when using it to try and test a RDC-DD, because the extended tripping period means the tester will miss its target, giving a test result of 8 mA when the device actually started tripping at 5.5 mA, allowing the tester to give a test result of 6 mA so you can say it passes.

The trip time for a Zappi RDC-DD is 900 mS, but the product standard allows up to 10 seconds (10,000 mS) at 6 mA and during the tripping period the RCD ramp test just keeps on ramping up and misses the target, giving the test current at the end of the test, not the current that started the tripping process.

Without guidance from the EVSE manufacturer it’s not actually possible to really determine if the test results you get are actually indicating a fault or not if for example you get a test result of 8 mA as stated in the article on the Zappi website.

Just because you have a meter that has had its software tweaked to get a pass when testing a Zappi EV charger doesn’t mean you know it will work with all EV chargers, because other EV chargers may have a longer trip time but still comply with the product standard.

So, like Type A RCD testing, to fully test RDC-DD you need a good understanding of the product standards, the individual manufacturers specifications for each of their products and the specific testing requirements for each individual device you are testing.

I might get shot down in flames and told I have have completely misunderstood the Zappi article and its implications, but as I understand it there are extremely good reasons why in the COP 9.6.6 says BS 7671 does not require tests of RDC-DD to be conducted, although it may be useful for fault-finding purposes, or where the functional test is specified in the EVSE instructions.

Not three years ago. 
Here’s another.

Are you saying the advertisement are inaccurate?

you seem to know more than me.

also there is a good thread on here where a Scandinavian country has taken issue with the RDC-DD. All about the contact separation distances and whether the device is protecting as stated.

cheers 

Unknown said:

also there is a good thread on here where a Scandinavian country has taken issue with the RDC-DD.

I understand that was associated with RCD functionality (and contact gap vs RCD product standards) in the particular product, among other issues raised. I understand those issues have now been, or are in the process of being, resolved.

We have been told not to do the five times tests on RCDs.

Have a look at the IET Guidance Note Three Table 2.17.

The test current for a Type A RCD has to be multiplied by the square root of two, which is 1.414 so the 1X test current is 42.42 mA pulsed D.C. and the 5x test current is 212.1 mA pulsed D.C. 

If you do a 5X test on a Hager 100 amp 30 mA Type A RCD and inject it with 212.1 mA of pulsed D.C. current using your tester it may not trip in 40 mS, complain to the manufacturer and you will be told you are not testing it correctly as the product standard allows a test current of up to 250 mA pulsed D.C. so you need reset your tester.

hager.com/.../updated-rccb-testing

It is even more of a problem if you tried testing the Type A RCD with a 5X Type AC test, because the test current would only be 150 mA AC current, not 250 mA pulsed D.C. so the RCD probably will fail to trip in 40 mS.

Again to fully test Type A RCDs you need a good understanding of the product standards, the manufacturers specifications and the individual testing requirements for each and every RCD you need to test.

Instead we “verify the effectiveness of the RCD” as noted on the bottom of the model EIC form in BS 7671 using a X1 AC test and haven proven it works with this test we then assume it’s within specification.

All the guidance on testing in the IET Guidance Notes and Codes Of Practice has been carefully considered and there are extremely good reasons why we are be told to change our working practices and stop doing things we have done ever since we trained and started working as electricians.

Also, as noted in the IET GN3 on page 97 RCDs are only rated for a finite number of operations, excessive testing isn’t good for them and may result in them actually failing when they are supposed to operate in a few weeks time, as Andy J said above testing today doesn’t mean they will actually work when needed to in a few weeks time.

Now I’m off to mow the lawn!

Again I don’t doubt your knowlede  other than It changed to recording X1 AMD 2 of BS7671 which has a fail after 300ms. Page ten for quick reference