All RCBOs?

[securespark]

Ring circuit conundrum - what to do?

Easy.....stop using the b@stards and install sensible radials instead.

 

[JohnW2]

Type F will become the go-to type as they are suitable for all types of equipment.

That wouldn't surprise me.

Once enough are made, like everything the price will plummet.

Undoubtedly. However, for a start, as I recently wrote about the introduction of RCDs, the prices won't start to plummet until the first few million people have had to pay seriously exorbitant prices for them.

However, I continue to find the situation to be intellectually unsatisfying/unsatisfactory. Despite a lot of trying, I still have not managed to find enough useful information to allow me to make a personal judgement as to whether the extent of the 'problem' justifies such changes, particularly in domestic environments - and my uncertainty about that becomes increasingly great the further one moves away from Type AC devices.

A lot of people seem to assume that "the PTB (or 'experts') know best" but I've seen more than enough examples of that being a questionable assumption to remain sceptical. If a doctor told you that your leg had to be chopped off, without any explanation or justification, would you simply accept that?

Kind Regards, John

 

[He who knows]

Type F will become the go-to type as they are suitable for all types of equipment.
Once enough are made, like everything the price will plummet.

EG, 5G phones were 4 figures when 5G was first available.
Now the cheapest 5G phone is around 200 quid.

Dunno.

Phones are disposable consumer tech items - people both want newer shinier ones all the time, and are pretty much need to because of the inability to replace batteries when they wear out after a few years.

According to Wikipedia over 1.5 billion mobile phones were sold in 2019. How many RCDs, I wonder.

 

[securespark]

Worldwide?

 

[EFLImpudence]

Easy.....stop using the b@stards and install sensible radials instead.

Yeah but, no but - I have (did).

It would be the same for radial socket circuits.

Limiting current to 66% of MCB rating.

 

[He who knows]

Type F will become the go-to type as they are suitable for all types of equipment.

Type B, surely?

 

[securespark]

The way I understood the situation was that Type F is able to handle equipment designed to be covered by all the other RCD types.

Presumably, these will, in time, become the go-to type as the cover all the bases.

I am happy to stand corrected though.

 

[He who knows]

Type B adds more tripping scenarios to type F.

531.3.3 (iv)

https://electrical.theiet.org/wiring-matters/years/2019/77-september-2019/which-rcd-type/

 

[securespark]

Yeah, misunderstood some bumf I got from the IET.

As you say, type B covers all scenarios.

 

[JohnW2]

Yeah, misunderstood some bumf I got from the IET. As you say, type B covers all scenarios.

Indeed. It's probably too far back for anyone to remember, but back on 'page 1' I posted the relevant bit of BS7671 which explains about these different 'Types'.

However, as I said, given that I am still looking for the 'evidence base' of the need for even Type A, I would certainly personally be very reticent to jump all the way to Type B 'just to be sure

As I also said, although I've never handled, let alone dissected, a Type B, I suspect that it may have to contain multiple electrical/electronic 'mechanisms' (all linked to the same mechanical trip mechanism) - which, if that's the case, could be an impediment to both miniaturisation and cost-reduction - but I really don't know.

Kind Regards, John

 

[He who knows]

Your first hurdle is probably the highest.

But if you've decided that yes, RCDs are good things to have, the issue then is "what type(s)?". The Wiring Matters article has useful examples, and the "extras" of Type B over F seem to be mostly of interest to commercial/industrial environments. EV chargers are often self-sufficient for earth leakage monitoring/protection, and I'm not sure how PV as distinct from inverters works - what would an RCD between PV panels and an inverter do?

Type A over AC? Probably a no brainer if you have decided you'd like RCDs, the price difference is minimal.

Type F.... Probably worth checking the MIs for new appliances, and testing RCDs under load, as the problem is not "false positives", it's "false negatives", so if you'd rather like to have ones which work...

 

[RF Lighting]

From working in a slightly specialist industry I've known about the issues surrounding VSDs and RCDs for a while and generally we would design RCDs out of the supply which is relatively straight forward on a nice new commercial or industrial installation.

It seems so obvious now, but it had never occurred to me that some modern domestic appliances contain a VSD despite hearing that very distinctive whine a VSD driven motor makes! I thing this is going to be where the real issue presents it's self.

Obviously having domestic sockets RCD protected is a good idea, so I can see it becoming standard to fit type F to at least socket circuits to cover all eventualities.

 

[JohnW2]

Your first hurdle is probably the highest. But if you've decided that yes, RCDs are good things to have, the issue then is "what type(s)?".

Indeed, except that regulations have almost completely trumped any thoughts about that "if".

The Wiring Matters article has useful examples, and the "extras" of Type B over F seem to be mostly of interest to commercial/industrial environments. EV chargers are often self-sufficient for earth leakage monitoring/protection, and I'm not sure how PV as distinct from inverters works - what would an RCD between PV panels and an inverter do?

Agreed, up to a point - but those "useful examples" are more-or-less the 'usual list', and get me no nearer to understanding the 'chapter and verse' of the facts behind all this.

Also, in common with most of what I've read on this topic, it is often far from clear as to whether they are talking about DC components (equal in L and N) which are present during 'normal operation' and DC components of the fault current (only in L) resulting from L-E faults.

Type A over AC? Probably a no brainer if you have decided you'd like RCDs, the price difference is minimal.

Essentially true. However, it remains the case that a high proportion of those 'on offer' are Type ACs.

.... not to mention the fact that (although I realise we're not taking too much notice of Type Bs),if one looks/searches for Type B ones, a very irritatingly high proportion of what one finds turn out to be Type AC or Type A B-curve ones. Whoever decided to use the same word to decribe two totally different characteristics of these devices really does need to be 'shot'

Type F.... Probably worth checking the MIs for new appliances,

I suppose that makes sense, but Type Fs are currently far from 'easy' to actually find (quite apart from the price, when one does find them.

... and testing RCDs under load, as the problem is not "false positives", it's "false negatives", so if you'd rather like to have ones which work...

I'm not sure it's necessarily that simple (even if one knows 'under which loads' to test). Provided one tests with the appropriate loads connected, that should address the possibility that a ('in normal service') DC component might prevent the device operating in response to an (AC) L-N imbalance due to a fault. However, if, as above, we are also talking about the possibility of a DC imbalance current due to a fault, then I presume that standard (present-day) testing procedures would not be able to confirm that the device trips under such circumstances?

Kind Regards, John

 

[JohnW2]

.... Obviously having domestic sockets RCD protected is a good idea, so I can see it becoming standard to fit type F to at least socket circuits to cover all eventualities.

As has been discussed, if you really wanted to "cover all eventualities", it would presumably have to be a Type B (with the attendant cost implications, at least at present)?

Kind Regards, John

 

[RF Lighting]

Yes sorry type B. The cost implications will go away once it becomes a common device.