Rcd fused connection unit

[telectrix]

That may be an option though I'd need to do some additional tests before I put the whole circuit on. I think in this instance budget is a rcd spur or nowt unfortunately

all depends on the state of the RFC> a stand alone RCD will probably be kicking round in the back of your van (there's 6 in my van, various makes), dead money. all you need is an enclosure.

 

[pc1966]

One of the curious aspects of the whole RCD-FCU issue is no one has come forward to say why the don't conform for additional protection. Or indeed what the "supplementary protection" is that they do provide.

There was an IET Q&A that just repeated some weaselly statement about standards, but did not say anything helpful. Someone could easily have given details, e.g. if the FCU standard lacks some aspect so some models are OK and other marginal, etc. But nothing, Which makes me deeply suspicions that is the reason: they are not willing to call out any make/model as not good enough since it meets the letter of the 7288 standard but lacks something obvious/adequate that 61008 has.

So if it has to be a FCU then at least get one of the reputable brands that gives the break capacity, etc, in the data sheet.

 

[Pretty Mouth]

Beama's RCD handbook has a table on p22 listing various RC devices and their suitability for certain applications. The only significant difference listed between a FCURCD and an RCCB or RCBO seems to be that they are not suitable for 'fixed wiring protection'. Exactly what is meant by that I am unsure.

They are however listed as suitable for personal protection (additional protection of persons or livestock against direct contact), protection against electrical fire, socket outlets 20A or less, and portable appliances 20A or less.

https://www.beama.org.uk/static/uploaded/aa78bfa3-2fe0-4982-b74dbe1e7caad081.pdf

 

[pc1966]

Beama's RCD handbook has a table on p22 listing various RC devices and their suitability for certain applications.

That is quite a useful guide book!

The only significant difference listed between a FCURCD and an RCCB or RCBO seems to be that they are not suitable for 'fixed wiring protection'. Exactly what is meant by that I am unsure.

Exactly!

One obvious limit is the FCU-RCD is limited to the 13A fuse so it can't really be used for anything beyond the equivalent of a fused spur or lighting circuit. Of course, in many cases (like this thread) that is exactly what is desired and it would appear they are sufficient for that job.

After all, what really is the difference between fixed wiring (that meets this <= 13A current limit) and flexible cables like an extension lead in terms of necessary protection?

 

[westward10]

In my eyes the whole thing with rcd spurs/sockets is unclear maybe why they are not included in BS7671. I certainly wouldn't want to be explaining if the worst was to happen why I employed one as opposed to following the requirements of BS7671.

 

[Pretty Mouth]

That is quite a useful guide book!

Exactly!

One obvious limit is the FCU-RCD is limited to the 13A fuse so it can't really be used for anything beyond the equivalent of a fused spur or lighting circuit. Of course, in many cases (like this thread) that is exactly what is desired and it would appear they are sufficient for that job.

After all, what really is the difference between fixed wiring (that meets this <= 13A current limit) and flexible cables like an extension lead in terms of necessary protection?

I struggle to see why using FCURCDs for additional protection would be a problem for minor additions and alterations, and do use them occasionally where the CU is obsolete and RCBOs are not available.

I've just sent an email to greenbrook (powerbreaker FCURCDs) to see if they can shed any light. Will update if/when a reply comes

 

[Dartlec]

I struggle to see why using FCURCDs for additional protection would be a problem for minor additions and alterations, and do use them occasionally where the CU is obsolete and RCBOs are not available.

I've just sent an email to greenbrook (powerbreaker FCURCDs) to see if they can shed any light. Will update if/when a reply comes

Will be very interesting to see what they come back with.

If they don't meet the 7671 requirements for additional protection, then in a domestic setting I don't really see what their intended usage would be, apart from maybe to comply with manufacturers instructions on a fixed load that wouldn't require an RCD otherwise? Any property needing them for fault protection would generally not be solved with a single FCU, or even RCD sockets everywhere.

The manufacturers of them certainly push them to the domestic market as a way of adding 'protection', but maybe they are careful to never claim they can add 'required' protection.

I've used them on occasions on minor works where a single socket or light is being added and there is not a simple solution at the CU without a complete board change, which the job does not justify. They seem like they should be a perfect solution to that problem.

 

[Dartlec]

That has the screenshot I obviously saw, though also some conflicting advice from elsewhere ?‍

Though it seems there has been a new version of the standard BS 7288 standard (2019 previously 2016) that has more onerous requirements, but without access to the standards I have no idea if it's made them more or less suitable..

Anyone notice if they put them back in for the DPC for AMD 2?

I looked it up and they haven't added them back in it appears (not in 531.3.4.1 at least)

Having said that it doesn't mention older standards such as 4293 either - so is that station the position that adding a socket onto an older but functioning BS4293 board would automatically not be compliant with BS7671?

 

[loz2754]

No, but adding a new BS4293 RCD would be non compliant because BS4293 is an obsolete standard, whereas BS EN 7288 is current.
Maybe...

 

[Ampo]

Wow thanks for all the responses, its clear to me that this subject is far from clear. Its a shame as it's a really important thing for us to have a definitive answer on. There are situations such as mine where a straight forward job can become awkward if we can't use them. I used to think they were fine and have added towel rails and so on in the past using them. In this instance with a couple outside 3a spurs I really can't see why the regs wouldn't allow it, seems overkill. I think the the end result of these sort of grey areas is that I won't be able to do it and then a less "awkward expensive" spark will simply chuck in standard spurs and walk away.