Rcd fused connection unit

[Lister1987]

Some additional court reporting from the Romford Recorder in this article, which also provides images of the DB to which this circuit had been connected and notable is the absence of additional protection. This work was undertaken in the early part of 2108, at which time AM3 was in force.

I believe there was an article in "Connections", the NICEIC magazine, that states that 7288 RCDs are considered acceptable as additional protection in the NICEIC's view. (Though it is as pointed out a deviation from BS7671 at the moment).

What that opinion is worth is up to the installer I guess - I did save a copy for reference so I'll see if I can find it...

Taken from an edition of Wiring Matters (https://electrical.------.org/bs-7671/faqs/qa-from-rcds-selection-types-and-testing-webinar/);

Are S-RCDs and FCU-RCDs (to BS 7288) recognised for additional protection in BS 7671?
RCDs to BS 7288 are not recognised for use as an RCD by BS 7671:2018. See Regulation Group 531.3.4.

Clause 1 of BS 7288:2016 states “SRCDs are intended for use in circuits where the fault protection and additional protection are already assured upstream of the SRCD.”

Further, Clause 0 of BS 7288:2018 states the devices are only suitable for additional protection against direct contact, and therefore cannot provide fault protection (e.g. where disconnection times cannot be met in a circuit), nor would they be recognised for additional protection against fire due to short circuits in appliances or flexible cables connected to the socket-outlet or connection unit.

However, there is nothing to stop accessories containing SRCDs to BS 7288 being fitted in electrical installations complying with BS 7671, as they comply with the relevant standards, although as stated the RCDs within them cannot be recognised for the functions of fault protection or additional protection for the purses of BS 7671.

-

The key point is that SRCDs to 7288 lack the sufficient clearances found in 61008/61009 devices, this is the reason they can't be used for Additional Protection. I'll see if I can dig out the relevant clauses from BS7288

 

[Dartlec]

Taken from an edition of Wiring Matters (https://electrical.electriciansforu...m-rcds-selection-types-and-testing-webinar/);

Are S-RCDs and FCU-RCDs (to BS 7288) recognised for additional protection in BS 7671?
RCDs to BS 7288 are not recognised for use as an RCD by BS 7671:2018. See Regulation Group 531.3.4.

Clause 1 of BS 7288:2016 states “SRCDs are intended for use in circuits where the fault protection and additional protection are already assured upstream of the SRCD.”

Further, Clause 0 of BS 7288:2018 states the devices are only suitable for additional protection against direct contact, and therefore cannot provide fault protection (e.g. where disconnection times cannot be met in a circuit), nor would they be recognised for additional protection against fire due to short circuits in appliances or flexible cables connected to the socket-outlet or connection unit.

However, there is nothing to stop accessories containing SRCDs to BS 7288 being fitted in electrical installations complying with BS 7671, as they comply with the relevant standards, although as stated the RCDs within them cannot be recognised for the functions of fault protection or additional protection for the purses of BS 7671.

-

The key point is that SRCDs to 7288 lack the sufficient clearances found in 61008/61009 devices, this is the reason they can't be used for Additional Protection. I'll see if I can dig out the relevant clauses from BS7288

Link doesn't work now it seems, but who was the answer from? Had anything changed since the other answer mentioned that states they are suitable RCD types for the purposes of additional protection? Or is this two different bodies coming to different conclusions?

But given this answer, where would one feasibly find any use for them then?

If suitable 30mA additional protection is available upstream, why would one use a FCU-RCD instead of a normal FCU, particularly when they all seem to be 30mA, so no selectivity available?

The standard was changed in 2019, so it would be interesting to see if anything improved or was altered in that, but us mere mortals can never get to see such precious resources of course.

But the fact that there is still a discussion about this without being able to get a clear definitive answer outside of Q&A in publications shows the failure of the 'system' to be clear or consistent.

 

[Pretty Mouth]

Taken from an edition of Wiring Matters (https://electrical.electriciansforu...m-rcds-selection-types-and-testing-webinar/);

Are S-RCDs and FCU-RCDs (to BS 7288) recognised for additional protection in BS 7671?
RCDs to BS 7288 are not recognised for use as an RCD by BS 7671:2018. See Regulation Group 531.3.4.

Clause 1 of BS 7288:2016 states “SRCDs are intended for use in circuits where the fault protection and additional protection are already assured upstream of the SRCD.”

Further, Clause 0 of BS 7288:2018 states the devices are only suitable for additional protection against direct contact, and therefore cannot provide fault protection (e.g. where disconnection times cannot be met in a circuit), nor would they be recognised for additional protection against fire due to short circuits in appliances or flexible cables connected to the socket-outlet or connection unit.

However, there is nothing to stop accessories containing SRCDs to BS 7288 being fitted in electrical installations complying with BS 7671, as they comply with the relevant standards, although as stated the RCDs within them cannot be recognised for the functions of fault protection or additional protection for the purses of BS 7671.

-

The key point is that SRCDs to 7288 lack the sufficient clearances found in 61008/61009 devices, this is the reason they can't be used for Additional Protection. I'll see if I can dig out the relevant clauses from BS7288

I can't get that link to work, it may be that the forum automatically censored it - I'm sure I had a similar problem before. Googling some of a sentence from what you posted took me to the webpage:

https://electrical.------.org/bs-7671/faqs/qa-from-rcds-selection-types-and-testing-webinar/

EDIT: yeah, looks like the forum censored it.

EDIT #2: Google "Are S-RCDs and FCU-RCDs (to BS 7288) recognised for additional protection in BS 7671?" including the quotation marks, it should be the first result.

 

[Lister1987]

Link doesn't work now it seems, but who was the answer from? Had anything changed since the other answer mentioned that states they are suitable RCD types for the purposes of additional protection? Or is this two different bodies coming to different conclusions?

But given this answer, where would one feasibly find any use for them then?

If suitable 30mA additional protection is available upstream, why would one use a FCU-RCD instead of a normal FCU, particularly when they all seem to be 30mA, so no selectivity available?

The standard was changed in 2019, so it would be interesting to see if anything improved or was altered in that, but us mere mortals can never get to see such precious resources of course.

But the fact that there is still a discussion about this without being able to get a clear definitive answer outside of Q&A in publications shows the failure of the 'system' to be clear or consistent.

https://electrical.electriciansforums.org/bs-7671/faqs/qa-from-rcds-selection-types-and-testing-webinar

Should now work.

BSI website lists the 2016 as the latest, with the standard currently under review.

The answer is definitive and clear as it's on black and white in Clauses 0 & 1 of the product standard

 

[Dartlec]

I can't get that link to work, it may be that the forum automatically censored it - I'm sure I had a similar problem before. Googling some of a sentence from what you posted took me to the webpage:

https://electrical.electriciansforu...rom-rcds-selection-types-and-testing-webinar/

EDIT: yeah, looks like the forum censored it.

Seems like the forum is editing the link somehow - it should be linking to the IET, but googling finds it.

That seems to be saying that it does offer additional protection for persons, but not for fire - but is the requirement for additional protection on domestic lighting circuits, for example, not designed for protection against direct contact for persons (with the fire protection part of an RCD being a benefit rather than a requirement?)

The lack suitability of use for fault protection is fair enough - though the fuse in the FCU part might meet that in certain circuits, might it not? Not sure if that is part of the 7288 standard or not.

 

[Dartlec]

https://electrical.electriciansforums.org/bs-7671/faqs/qa-from-rcds-selection-types-and-testing-webinar

Should now work.

BSI website lists the 2016 as the latest, with the standard currently under review.

The answer is definitive and clear as it's on black and white in Clauses 0 & 1 of the product standard

It looks like the 2016 standard actually only came into force in November 2019 - and that the clauses you mention were added then perhaps.?

Some interesting discussion here - Electrical Blog - Electrical Advice | Free Electricians Advice Forum - https://electriciansforums.co.uk/discussions/viewtopic/1037/24702#forums-view-topic

If the link works. (Edit: external links seem to being mucked up at the moment... add communities PERIOD ------ PERIOD org in place of electriciansforums.co.uk and it will work....

EDIT 2: GRRRR - the spam filter seems to be preventing any external website links at all... or really doesn't like linking to IET communities!

Search for “Additional change agreed following April 2019 meeting to include reference to BS 7288 for SRCD and FCURCD in clauses 531.3.4.1 & 531.3.4.2”

Which discusses the confusion too - but also seems to have a quote from an IET page that no longer exists - that said:

“Additional change agreed following April 2019 meeting to include reference to BS 7288 for SRCD and FCURCD in clauses 531.3.4.1 & 531.3.4.2”

Which suggests that at one point they did think it was a mistake and would add it - that seems to be where the "Connections" answer was coming from.

The IETs link (which was from a webinar in Dec 2020 so more recent) seems clear - but outside of buying the actual standard, there doesn't seem to be a definitive statement in a published guide anywhere that states they cannot be used for the only scenario when anyone would actually buy one?

I'm betting that the manufacturers instructions for the currently on sale RCD-FCUs don't say that upstream additional protection must be in place?

 

[loz2754]

I just tried posting several links to different websites, but the forum borks them up by changing the domain name.

 

[Dartlec]

https://electrical.electriciansforu...rom-rcds-selection-types-and-testing-webinar/

Apparently the forum software does not allow linking to IET communities, however you try.... even putting it in with spaces and the word DOT in between (not as a link) changes it to electriciansforums.org domain....

 

[Pretty Mouth]

I take issue with that Q+A article. 3 different questions are asked on SRCDs and FCURCDs, and the exact same cut-and-paste reply is given to each, like it was written by a politician.


Clause 1 of BS 7288:2016 states ”“SRCDs are intended for use in circuits where the fault protection and additional protection are already assured upstream of the SRCD.”″

Well, obviously an RCD socket isn't going to protect the circuit itself, upstream of the device.


Further, Clause 0 of BS 7288:2018 states the devices are only suitable for additional protection against direct contact, and therefore cannot provide fault protection (e.g. where disconnection times cannot be met in a circuit),

irrelevant, they weren't asked about fault protection.

nor would they be recognised for additional protection against fire due to short circuits in appliances or flexible cables connected to the socket-outlet or connection unit.

No RCD will, without having integral overcurrent protection, protect against short circuit. Again, irrelevant.

 

[pc1966]

From the IET's answers it seems they are chocolate fireguards as, to be complaint with the 18th, you need "additional protection" and once you have that what is the point of a RCD socket or FCU?

However, one interesting point is the standard stating:

...only suitable for additional protection against direct contact, and therefore cannot provide fault protection (e.g. where disconnection times cannot be met in a circuit)...

Now my reading of that is you could use them to supply outside sockets where electric shock is the key risk, provided the disconnection times are being met by means of an acceptably low Zs value. However, you could not use them to deal with a long cable and low static load where you meet the VD requirements but can't disconnect in under 0.4s on the OCPD.

 

[Dartlec]

I take issue with that Q+A article. 3 different questions are asked on SRCDs and FCURCDs, and the exact same cut-and-paste reply is given to each, like it was written by a politician.


Clause 1 of BS 7288:2016 states ”“SRCDs are intended for use in circuits where the fault protection and additional protection are already assured upstream of the SRCD.”″

Well, obviously an RCD socket isn't going to protect the circuit itself, upstream of the device.


Further, Clause 0 of BS 7288:2018 states the devices are only suitable for additional protection against direct contact, and therefore cannot provide fault protection (e.g. where disconnection times cannot be met in a circuit),

irrelevant, they weren't asked about fault protection.

nor would they be recognised for additional protection against fire due to short circuits in appliances or flexible cables connected to the socket-outlet or connection unit.

No RCD will, without having integral overcurrent protection, protect against short circuit. Again, irrelevant.

Is "additional protection against fire due to short circuits in appliances or flexible cables" even something that is a specific requirement in any installation? The additional protection requirements for most domestic circuits is more about the protection of direct contact for people I'd assume.

The Wiring Matters page from September 2019 - Which RCD Type? - Electrical - https://bit.ly/3d6iJFy

EDIT: LOL, can't even write IET and electrics with any domain name near it or the software recognises it as an attempt to sneak a dodgy link in

States

Residual Current Devices (RCDs) are safety switching devices. They are designed to provide safety for three types of protection; these are:

1. Fault Protection. Any tripping current dependent on the resistance of the earth path. (Regulations 411.4.204; 411.5.1; 531.2).
2. Additional Protection. RCDs not exceeding 30 mA tripping current. (415.1).
3. Fire Protection. A tripping current not exceeding 300 mA. (422.3.9).

Then includes 7288 as one of the RCD types - and at no point mention that they cannot provide additional protection or require additional protection to be present already.

Though interestingly it only lists: Socket Outlet incorporating a Residual Current Device (SRCD) with or without overcurrent protection BS 7288, and not the FCU version?

 

[loz2754]

RCDs: Selection, Types and Testing webinar questions and answers

Here you can find the answers to the questions we had submitted during the above webinar on 1 December 2020.

bit.ly

Got round it by using a URL shortener.

 

[Pretty Mouth]

Is "additional protection against fire due to short circuits in appliances or flexible cables" even something that is a specific requirement in any installation? The additional protection requirements for most domestic circuits is more about the protection of direct contact for people I'd assume.

Agree. All the usual things that require additional protection (sockets, outdoor equip, cables buried <50mm, bathrooms and so on) are either found in chapter 41 (protection against electric shock) or refer to reg 415.1, which is in chapter 41.