Does this comply with 314?

[Octopus]

Been at a place today.......... brand new loft conversion.......... so an additional CU has been fitted for the lights and sockets ......................

Thinking specifically about 314.2 :

I would say that it doesn't............

Opinions please

and more to the point, this conversion probably cost about £45k so using RCBO's wouldn't have been noticed................

The last one I saw was where a new single RCD board had been used for the entire house and loft conversion.............. why do people do this?

 

[Octopus]

Being pragmatic, I think it is most useful and sensible to have lighting and power in a given area on different RCDs and whilst one might argue about the exact interpretation of 314 it would be poor design not to do this, and hence arguably non-compliant.

Thank you .......... which is the way I think about this subject.

Still nobody offering up why we ditched split load boards, and adopted dual RCD rather than single up front boards...............

 

[Midwest]

Really? The maximum permissible on a 13A plug is 3.5mA, I would be most surprised to see that much leakage from any domestic appliance or have they gone silly with filtering these days? I don't PAT any domestics but I see a lot of PAT results from industrial equipment and no single piece of kit ever reaches 3mA. Even the media systems that I build, with maybe 20 pieces of equipment built into a rack all run from one plug, rarely reach 2mA.

Out of curiosity, where does that figure come from?

 

[Richard Burns]

Thank you .......... which is the way I think about this subject.

Still nobody offering up why we ditched split load boards, and adopted dual RCD rather than single up front boards...............

Split load boards were relevant to the 16th Edition, protecting socket outlets with 30mA RCD protection and leaving the rest unprotected. With the advent of greater RCD protection with 17th Edition an appropriate method of protection was dual RCD boards, this addresses both the increased RCD protection required and the division of circuits guidelines in a practical way. For a domestic situation this is a practical approach, remembering the the division of circuits is worded clearly to indicate that this is not an absolute requirement.
This could be taken by common practice to be the minimum standard of compliance with the regulations.
It is always possible to exceed the minimum standard and fit an all RCBO board. I think there would be no doubt that this provides a greater division of circuits but at present the cost benefit analysis is still wavering and comes down in favour of the dual RCD board (by my analysis, but not by yours). As the cost of RCBOs comes down this will, and is, shifting the balance of what is reasonably practicable.

I would say that overall in a domestic property a single dual RCD board or two upfront RCD boards is compliant but a single all RCBO board would exceed the minimum requirements.

 

[Octopus]

S
It is always possible to exceed the minimum standard and fit an all RCBO board. I think there would be no doubt that this provides a greater division of circuits but at present the cost benefit analysis is still wavering and comes down in favour of the dual RCD board (by my analysis, but not by yours).

If I'm challenged about my preference for fitting RCBO boards - I explain what happens when 1 RCD trips on a dual board - and most people then agree RCBO boards are better.

As for minimising inconvenience and 314.2 all it would take is 1 or 2 more sentences in 7671 to clarify.

I will continue not to fit small up front boards if the circuits contained in the the same room(s).

Last month I was working on an older MK split load board - instead of moving a circuit from the non RCD side to the RCD side, I opted to fit a RCBO - sure it cost the client about £50 but much better in the long run.

Personally I'd like to see boards split RCD / RCBO .......... sockets on RCBO's

 

[Lucien Nunes]

Out of curiosity, where does that figure come from?

543.7.1.1

 

[Deleted member 9648]

I think the view that the installation in the original post is non compliant is being rather overlapped with the view that there is a better design alternative.
The two are entirely different things. Yes there is a better design alternative, but given that there is a division of circuits over the installation as a whole, it is compliant.
Like a lot of Bs7671 314.2 is open to various interpretations and does not specifically state that circuits within the same room must not be subject to loss from a single protective device.

 

[Risteard]

I need somebody to remind me why we ditched split load boards and introduced dual RCD's - somebody must have some memory of this?

Because under the 16th Edition we didn't tend to RCD protect everything.

 

[Ian1981]

SPlit load dual rcd consumer units came out when the 17th edition introduced the requirement for more rcd protected circuits for multiple reasons as with the 16th cables where not required to have additional protection to them where buried in walls <50 mm

 

[seltechpc]

Really? The maximum permissible on a 13A plug is 3.5mA, I would be most surprised to see that much leakage from any domestic appliance or have they gone silly with filtering these days? I don't PAT any domestics but I see a lot of PAT results from industrial equipment and no single piece of kit ever reaches 3mA. Even the media systems that I build, with maybe 20 pieces of equipment built into a rack all run from one plug, rarely reach 2mA.

I decided to recheck these readings and the results were 1.2mA, 1.3mA and the newest appliance was 1.96mA. A bit red faced at quoting 3mA but these do add up to almost 4.5mA. The hob was around 2mA which starts to seem these electronic appliances with various filters to meet EMC specs are increasing the leakage currents to levels where it can lead to unwanted tripping of the RCD's, even with a high integrity CU.
Add more appliances and a few computers and little thought given to which rings they are plugged into can give rise to nuisance tripping.

 

[Octopus]

SPlit load dual rcd consumer units came out when the 17th edition introduced the requirement for more rcd protected circuits for multiple reasons as with the 16th cables where not required to have additional protection to them where buried in walls <50 mm

I realise this but why a dual RCD and not a single up front RCD?

 

[Midwest]

I realise this but why a dual RCD and not a single up front RCD?

I don't think this kind of subterfuge, is going to work Murdoch

 

[Ian1981]

Then you run the risk of losing all your power if the rcd trips.
At least with 2 you don't loose all power to all circuits.
Of course you can do that arrangement if you wish but I know you wouldn't
I haven't read the full thread so I feel I'm missing the point?

 

[Ian1981]

Or do you feel only rcbos are the only solution?
Each individual circuit?

 

[Octopus]

Then you run the risk of losing all your power if the rcd trips.
At least with 2 you don't loose all power to all circuits.
Of course you can do that arrangement if you wish but I know you wouldn't
I haven't read the full thread so I feel I'm missing the point?

Have you read my opening post ?

 

[Ian1981]

Db for the loft sockets and lights on one rcd.
Your worried about loss of power to the whole loft.
I'd say that it's fine.
The rest of the house wouldn't be affected I wouldn't be worried about it.
I see the point in individual rcbo protection but individual rcd protection for all circuits isn't a requirement tho certainly not prohibited.
Upto the individual installer I'd say.