All RCBOs?

[He who knows]

You presumably won't have seen, but I am one of those who has been known to quite often question the 'need' for RCDs (benefit of having) RCDs of any type!

I can't deny that the increasing regulatory requirement will march on relentlessly, regardless of any thoughts I may have, but I don't think one should necessarily assume that, in terms of 'big pictures', the 'advances' are necessarily all that 'sensible'.

The law of diminishing returns kicked in a while ago.

AFDDs will be next, and then the arguments can be about one up front for the entire installation vs divvying up the circuits into 2 or 3 groups vs combined MCB/AFDD or RCBO/AFDDs. Good luck to the miniaturisers getting a Type B RCBO with AFD into a one-module case...

I think that the people who write the regs fear that they'll be declared redundant if they can't keep coming up with "our work is not done - there must be a new version".

 

[He who knows]

I have, and have had for many years, circuits protected by Type AC RCDs which definitely do (simultaneously) feed several 'electronic power supplies', and I would really love to have some proper understanding of the possible implications of this!

Do you test your RCDs with the devices powered up?

 

[Swwils]

If it helps my 2020 new build is 15 circuits grouped over 2 type AC RCDs.

I've invited the NICEIC for a site visit so we will be able to see (or maybe not) what they say about this kind of design on what I assume is a 18th edition certificate.

 

[ericmark]

You may be sure that as the prevalence of Type F & B RCCBs increases, then as soon as the test equipment manufacturers are in a position to produce testers they'll be lobbying the regulators to require their use. And making them is probaby not hard - no trip loop testers stop RCDs tripping by saturating the core with a DC component.

Anybody experienced their loop tester tripping F or B RCCBs?

I think you have hit the nail on the head, manufacturers have made a device and have lobbied the regulators to require their use, not that it is really required.

I made a mistake, and as a result have all type AC, I have assessed the risk, and feel with all RCBO it is very unlikely an earth leakage fault and a DC component fault will happen at the same time, I ordered up some type A to replace them but after 8 months still had not arrived so cancelled.

 

[JohnW2]

You may be sure that as the prevalence of Type F & B RCCBs increases, then as soon as the test equipment manufacturers are in a position to produce testers they'll be lobbying the regulators to require their use.

I suspect that you don't need to wait. My fairly ancient Fluke 1652 has the facility to test Types AC and Type A, and its (equally ancient) manual says that its bigger brother (1654, which I don't have) is also able to test Type Bs.

I must say that it has never occurred to me to test my Type ACs with the meter in its 'Type A' mode - but that is certainly something to go onto my 'experiments to try' list

Kind Regards, John

 

[RF Lighting]

I can’t provide you with any figures but as I look around my own home every circuit supplies at least one electronic device.

I have seen plenty of RCDs which will not trip or take too long to trip when tried with an RCD tester if the load is connected. The norm was to retest the RCD in isolation and if it passed this then forget it and move on. We were told that it was capacitance in the circuit and that it wasn’t an issue.

Perhaps these RCDs were actually being affected by the type of load and really would fail to trip in the required time when they are actually needed to perform.

Ultimately it’s up to you what you do with your installation, but I will continue to play it safe and not fit AC type RCDs and advise others to do the same.

 

[JohnW2]

The law of diminishing returns kicked in a while ago. .... AFDDs will be next, and then the arguments can be about one up front for the entire installation vs divvying up the circuits into 2 or 3 groups vs combined MCB/AFDD or RCBO/AFDDs. Good luck to the miniaturisers getting a Type B RCBO with AFD into a one-module case... .... I think that the people who write the regs fear that they'll be declared redundant if they can't keep coming up with "our work is not done - there must be a new version".

All totally agreed.

In some specific instances I may be wrong, but I can't help but think that most of this, arguably from RCD onwards, has been a case of things being introduced because technological advances have meant that "they can", rather than that a genuinely perceived 'need' resulted in the technological advances being made - in other words, potentially "solutions looking for problems"!

Kind Regards, John

 

[RF Lighting]

I’m still mad about them putting airbags in cars. Fancy trying to make things safer as technology advances.

 

[JohnW2]

Do you test your RCDs with the devices powered up?

No. Probably pretty irrationally (except, perhaps, in relation to particularly sensitive loads), I've always been a bit nervous to do that. However, I may try - and, in any event, as I've just written, I've just realised that I have the ability to at least test my Type AC ones with a "Type A tester" - which will be interesting.

Kind Regards, John

 

[JohnW2]

I can’t provide you with any figures but as I look around my own home every circuit supplies at least one electronic device.

Similar here - and, as I've said, there are some circuits supplying many electronic devices

I have seen plenty of RCDs which will not trip or take too long to trip when tried with an RCD tester if the load is connected. The norm was to retest the RCD in isolation and if it passed this then forget it and move on. We were told that it was capacitance in the circuit and that it wasn’t an issue.

As I said, I've always been rather nervous about testing RCDs with electronic loads connected and 'working', but maybe I should try. More to the point, now that I've discoved/realised that I have the ability to do a "Type A test", I'm certainly going to try that!

Perhaps these RCDs were actually being affected by the type of load and really would fail to trip in the required time when they are actually needed to perform.

Perhaps. That's obviously the suggestion that some people are making, whether it is based on theory, myth or fact.

Ultimately it’s up to you what you do with your installation, but I will continue to play it safe and not fit AC type RCDs and advise others to do the same.

Fair enough. It's not really a question of 'what I do with my installation', since I don't envisage any of my CUs or devices (unless they fail) needing to be replaced in the foreseeable future, and, in the meantime, I'm certainly not going to go around replacing all my Type AC RCDs with Type A ones. As for advising others, as I've said, I haven't yet been able to find anything like enough information to enable me to offer any usefully-informed advice.

Kind Regards, John

 

[JohnW2]

I’m still mad about them putting airbags in cars. Fancy trying to make things safer as technology advances.

I may be wrong, but I strongly suspect that they were developed because of a perceived 'need' (benefit they would offer), not just because it became technological possible to produce them. I also feel sure that there is plenty of empirical data out there which provides a handle on the magnitude of the benefits which they provide.

I am in no way opposed to beneficial technological advances, an incredible number of which I have seen during my lifetime to date. However, almost all of my working life has been based on 'evidence-based' developments and practices - so, whether we are talking about types of RCDs, SPDs, AFDDs or whatever, I really want to see some evidence about the benefit they offer before I can decide, personally, whether I regard them as 'worthwhile'.

Of course, my 'personal opinion' is of limited usefulness, other than to myself - since, as has been observed, once a 'technological advance' has arisen (in fields such as we are discussing), it's usually only a matter of time before regulatory compulsion to implement them follows - regardless of anyone's 'personal opinion' (or, indeed, regardless of the strength of evidence that the 'advance' offers a worthwhile benefit).

Kind Regards, John

 

[He who knows]

Good luck to the miniaturisers getting a Type B RCBO with AFD into a one-module case...

Well, there ya go. OK - it isn't a type F or B, but they're getting there.

Crabtree & Wylex - SP+N Type A RCBOs with AFD in 18mm packages. Normal height too.

Only £155 - £186 list at CEF.

Hahaha

 

[JohnW2]

Well, there ya go. OK - it isn't a type F or B, but they're getting there. Crabtree & Wylex - SP+N Type A RCBOs with AFD in 18mm packages. Normal height too. Only £155 - £186 list at CEF. Hahaha

Quite so.

I think that's why we have to very seriously consider whether there really is an adequate 'need' for, or benefit to be had from, such things to justify their cost (rather than just a "because we can do it" situation)...

... if, very roughly (and 'conservatively'), we say that's about £130 more than a bog-standard Type AC RCBO, that there's an average of about 8 per CU, and around 25 million domestic electrical installations, I make that around £26 billion ... one then has to think about the benefits to be had by re-directing that £26 billion in other directions - such as road safety, or 'merely' just addressing the problems of the 'disadvantaged' and/or poverty-stricken.

Kind Regards, John

 

[RF Lighting]

RCDs used to be really expensive when they first came out and now they’re not any more.

 

[Swwils]

Hopefully it's all preparation for ditching ring finals!