Replacement consumer unit necessary?

[flameport]

, it's about time that some decent attempts were made (and the results made available) to address the fact that the behaviour of Type AC RCDs with non-sinusoidal currents is "undefined and mostly unknown".

Already done.
Plenty here: https://scholar.google.com/scholar?hl=en&as_sdt=0,5&q=residual+current+devices+AC+A&btnG=

 

[JohnW2]

Already done. Plenty here: https://scholar.google.com/scholar?hl=en&as_sdt=0,5&q=residual+current+devices+AC+A&btnG=

Thanks. I think I'm probably familiar with a fair number of those articles, since I've frequently done similar searches, but there may well be some there which will be new for me. Watch this space!

At least someone has now offered some suggestions. I've been asking, here and elsewhere, for at least a couipleof years for 'pointers', with no particularly responses at all.

Kind Regards, John

 

[Risteard]

Do you want to edit that?

No.

 

[JohnW2]

No.

Eh? - don't most/all electricians have the means of tested a Type AC RCD?

 

[Risteard]

Eh? - don't most/all electricians have the means of tested a Type AC RCD?

Precisely my point.

 

[JohnW2]

Precisely my point.

I'm confused, and can but presume that someone has not been properly reading (or understanding) what they have been responding to .....

And then there is the thorny issue of so many sparks unable to actually test type A RCDs

How would they be unsure of how to test them?

because their test kit hasn’t got the ability to test them properly

Their test equipment doesn't have an AC RCD test facility?

Do you want to edit that?

No.

Eh? - don't most/all electricians have the means of tested a Type AC RCD?

Precisely my point.

 

[flameport]

BS7671 only requires that RCDs are tested with AC at the rated residual current.
Any RCD tester would be suitable for that.

Even if using the older information and testing with a specific 'type A' test, that's not new either, manufacturers such as Wylex and MEM (now Eaton) have been selling Type A devices in the UK for 20+ years, and test equipment has been available with that option for a similar amount of time.

 

[Murdochcat]

BS7671 only requires that RCDs are tested with AC at the rated residual current.
Any RCD tester would be suitable for that.

Even if using the older information and testing with a specific 'type A' test, that's not new either, manufacturers such as Wylex and MEM (now Eaton) have been selling Type A devices in the UK for 20+ years, and test equipment has been available with that option for a similar amount of time.

so what’s the point in testing the RCD at all then ?

might as well forget the test altogether

 

[flameport]

so what’s the point in testing the RCD at all then ?

Ask JPEL/64.

Even if testing Type A specifically (which isn't required), how many electricians working today have testing equipment so ancient that it doesn't have the option for Type A?

 

[JohnW2]

BS7671 only requires that RCDs are tested with AC at the rated residual current.

It does. It's interesting to see how the note in 643.8 has changed with Amd 2. Prior to the amendment (when there was no reference to Types of RCD), the note indicated the requirement that testing should confirm a disconnection time of 'within 40 ms' at a residual current of 5 x IΔn or above. Amd 2 now includes "regardless of Type" and requires a disconnection time of '300 ms maximum' with a residual current of IΔn. I wonder why they've made that change?

Any RCD tester would be suitable for that.

It would, but it seems odd that if it is felt necessary to require a Type A RCD, that BS 7671 is happy with a test which does not confirm that Type A behaviour is working satisfactorily. In other words, BS761 could 'deem' a Type A RCD to have 'passed' an RCD test even if its functioing were no better than that of a Type AC one.

Even if using the older information and testing with a specific 'type A' test, that's not new either, manufacturers such as Wylex and MEM (now Eaton) have been selling Type A devices in the UK for 20+ years, and test equipment has been available with that option for a similar amount of time.

Indeed so. In fact, I wonder if (m)any RCD testers or MFTs do not have the ability to test Type A RCDs to at least some extent (beyond a 'Type AC' test) Even my humble Fluke 1562 has the ability to test Types A (at least with a 'half-wave' waveform, if not other non-sinusoidal waveforms), as well as a DC test for Type Bs ....

Kind Regards, John

 

[JohnW2]

Ask JPEL/64. Even if testing Type A specifically (which isn't required), how many electricians working today have testing equipment so ancient that it doesn't have the option for Type A?

As I've just written, my Fluke 1562, which is not very young and is a pretty 'basic' MFT, has the ability to test Type As with a half-wave waveform - so, as you say, I imagine that many/most electricians probably have at least that degree of ability to test Type As

To what extent testing just with a 'half-wave' waveform proves very much, I'm not so sure.

Kind Regards, John

 

[JohnW2]

..... Type A will operate with non-sinusoidal current, which is what the majority of electrical equipment in use today creates.
..... For circuits that do have a possibility of DC current or higher frequencies, other types of RCD will be required.

In relation to the above, having just had cause (in a different thread) to remind myself about what sort of RCD testing my MFT (a Fluke 1652) can do, at least a couple of questions arise...

For testing Type A RCDs, my 1652 appears to offer just one 'non-sinusoidal' waveform, namely a 'half wave' (i.e. a half-wave rectified sine wave). That leads to the questions (more may follow).

1... A half-wave rectified sine wave has a very large DC component (since the entire waveform is on the same side of zero). In view of the above comment, does that mean that a Type A RCD is not suitable in the face of such a waveform?

2... At least partially dependent upon the answer to the first question, but is use of a half-wave rectified sine wave satisfactory/appropriate for testing a Type A RCD

Kind Regards, John