Does this comply with 314?

[Deleted member 9648]

^^ ha ha.

Seeing as nobody can explain why we can fit dual board now, I have come to conclusion that my interpretation of 314.2 is correct in the op and my example stands as a non compliance to the regs.

314.2 merely states that due account shall be taken of the consequences of the operation of any single protective device

As the rest of the installation will not be affected by the operation of the device in question at the present time it complies.

 

[Midwest]

Hit, nail and head spring to mind..... I stopped fitting dual RCD boards when AMD3 boards arrived - far, far, far better when something trips.

For a larger property, I'd fit a high integrity CU with 2 or 3 RCBO's. The off the shelf RCBO populated CU's only come seem to come with 6 or so RCBO's, to make one up yourself is a tad expensive?

My own pad, which I did a few years ago, has a RCBO CU and single RCD CU for ono important circuits (314.2 considered ).

 

[Midwest]

I'd give up Murdoch

 

[Octopus]

I'd give up Murdoch

Not yet!

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

Or as I said 314.2 my interpretation is correct!

There's nothing worse than a single RCD up front board ....

 

[Lucien Nunes]

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.

The main point of a 30mA RCD is to protect against electric shock, which is most likely to occur when someone has an accident of some kind with a portable appliance. To plunge them into darkness within a fraction of a second of having been shocked, simply on the grounds of economy, is not sensible. I think we get blinkered to this purpose of RCDs because we are so used to being called on to troubleshoot nuisance trips, we don't associate their operation with the moment they cut short a possibly fatal shock that could leave someone in a vulnerable physical condition.

On the subject of convenience, many elderly and infirm people are most at risk on the stairs. They might safely be able to cross the room to turn on the ceiling light if they have been using a table lamp when the RCD serving the ring trips, but would not venture downstairs or run a cable up if the stairwell and room lighting circuits went off too.

It was very revealing, I checked 3 Miele appliances and found they were all around 3mA leakage; one of them was a brand new dishwasher.

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.

 

[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