There are reasons why we don’t test RDC-DDs, mainly that it cannot be done correctly with an electricians installation tester

support.myenergi.com/.../4403885493265-zappi-6mA-DC-protection-to-IEC-62955

You may want to have a word with Megger and Metrel then. And yes we do test them. BS7671 states an AC test is required for verification. But if you work for an authority or a public supplying company you will prove the device operates beyond 7671 requirements to keep possibility of anything litigious at bay.  

Sparkingchip said:

There are reasons why we don’t test RDC-DDs

Agreed ... this is also covered in the newly published 5th Ed of the IET CoP for EV Charging Equipment Installation (Section 9.6.6):

The reason it didn't appear in previous Editions, is that testing of RDC-DDs is not mandated in BS 7671. Whilst some manufacturers may recommend certain tests for commissioning, maintenance or fault-finding, it would appear that somehow the industry had come to see RDC-DD testing as some sort of 'requirement'.

The important issue to consider, is that the parameters of test for an RDC-DD (as you have indicated) are not the same as for the additional tests of a Type B RCD, and are not taken into account in BS EN IEC 61557-6.

Unknown said:

You may want to have a word with Megger and Metrel then.

The manufacturers of that equipment may have taken into account the parameters for RDC-DD - this is also covered in the IET CoP Section 9.6.6 as above "test instrument manufacturer’s specifications or user instructions should be checked to see that the test instrument is designed to conduct tests of RDC-DDs."

Unknown said:

BS7671 states an AC test is required for verification.

Of an RCD ... not an RDC-DD. (Reg 643.7.1 for ADS, and Reg 643.8 for additional protection, only mention RCD).

If RCD functionality is included in a single device to BS IEC 62955, then it's an RDC-PD not an RDC-DD, and the RDC-PD would be tested using Type AC as per RCD (and the manufacturer may also state conformity to BS EN 61008, BS EN 61009, BS EN 60947-2 or BS EN 62423 as well). Reg 722.531.3.101 of BS 7671:2018+A2:2022 lists the requirement RCDs must comply with for EV charging installations in the last para, and , BS IEC 62955 is not listed there - it is only listed for RDC-DDs in (ii) above that, where it must be used in conjunction with a Type A or Type F RCD, and it is therefore the Type A or Type F that would undergo the Type AC test, not the RDC-DD.

Unknown said:

But if you work for an authority or a public supplying company you will prove the device operates beyond 7671 requirements to keep possibility of anything litigious at bay.  

Agree 1000 % (no typo), although as above, you'd definitely need to check the test instrument has the right parameters, which I think is what Sparkingchip  was getting at in his post.

Sparkingchip said:

There are reasons why we don’t test RDC-DDs

Agreed ... this is also covered in the newly published 5th Ed of the IET CoP for EV Charging Equipment Installation (Section 9.6.6):

The reason it didn't appear in previous Editions, is that testing of RDC-DDs is not mandated in BS 7671. Whilst some manufacturers may recommend certain tests for commissioning, maintenance or fault-finding, it would appear that somehow the industry had come to see RDC-DD testing as some sort of 'requirement'.

The important issue to consider, is that the parameters of test for an RDC-DD (as you have indicated) are not the same as for the additional tests of a Type B RCD, and are not taken into account in BS EN IEC 61557-6.

Unknown said:

You may want to have a word with Megger and Metrel then.

The manufacturers of that equipment may have taken into account the parameters for RDC-DD - this is also covered in the IET CoP Section 9.6.6 as above "test instrument manufacturer’s specifications or user instructions should be checked to see that the test instrument is designed to conduct tests of RDC-DDs."

Unknown said:

BS7671 states an AC test is required for verification.

Of an RCD ... not an RDC-DD. (Reg 643.7.1 for ADS, and Reg 643.8 for additional protection, only mention RCD).

If RCD functionality is included in a single device to BS IEC 62955, then it's an RDC-PD not an RDC-DD, and the RDC-PD would be tested using Type AC as per RCD (and the manufacturer may also state conformity to BS EN 61008, BS EN 61009, BS EN 60947-2 or BS EN 62423 as well). Reg 722.531.3.101 of BS 7671:2018+A2:2022 lists the requirement RCDs must comply with for EV charging installations in the last para, and , BS IEC 62955 is not listed there - it is only listed for RDC-DDs in (ii) above that, where it must be used in conjunction with a Type A or Type F RCD, and it is therefore the Type A or Type F that would undergo the Type AC test, not the RDC-DD.

Unknown said:

But if you work for an authority or a public supplying company you will prove the device operates beyond 7671 requirements to keep possibility of anything litigious at bay.  

Agree 1000 % (no typo), although as above, you'd definitely need to check the test instrument has the right parameters, which I think is what Sparkingchip  was getting at in his post.

Depends on your level of responsibility. Megger adverts state the test RDC. The regulations and COP are a minimum requirement. Some engineers work to a minimum.

Unknown said:

Depends on your level of responsibility.

Unknown said:

The regulations and COP are a minimum requirement. Some engineers work to a minimum.

The CoP doesn't say "don't". I do concur that BS 7671 is the "minimum standard", and the CoP itself has recommendations that exceed BS 7671 requirements.

The CoP actually says "There might be some good reasons to test RDC-DD, but check your instruments are suitable first." - and again, you can go further if you wish.

Unknown said:

Megger adverts state the test RDC.

Agreed ... but even then, it's important with some models (of this and other manufacturers) to check you have the correct firmware to do the test, as discussed here.

We agree  I have liked talking to you. You have made the effort to learn. Type B is required for mode four. High frequency harmonics will create thermal damage to a type A plus RDC.

have a good evening mate, I am off for beer.

kind regards

Mark