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AFDD (Regulation 421.1.7)

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AFDD (Regulation 421.1.7)

Posted by SJR on Apr 25, 2019 1:49 pm

I'm looking to design the refurbishment of a hotel ('Premises with Sleeping Accommodation') and need to know if all new final circuits whether or not they supply bedrooms will need to be provided with AFDD. I appreciate this use of AFDD for final circuits supplying bedrooms but not sure if this should apply to other areas of the building i.e. existing plantrooms which includes socket circuits, lighting circuits and final radial circuits to fixed equipment. The first two of words of the regulation states 'if used,' which is vague in my opinion and may imply their use subject to a risk assessment. If this is the case, who carries out this risk assessment?

Thanks,

Stephen 

Re: AFDD (Regulation 421.1.7)

Posted by mapj1 on Apr 25, 2019 4:49 pm

It may not help, but the consensus of these 3 previous discussions was  'it depends', verging towards 'probably not unless the fire risk justifies it or the prices fall to approach those of an RCBO' .
The regs really say you must consider it and fit them if needed.

https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=106311&STARTPAGE=1&FTVAR_FORUMVIEWTMP=Linear

https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=107224
https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=105540

right now prices have some way to go, even for the 16A ones made in bulk to be used on the continent.

https://www.automation24.co.uk/arc-fault-detection-devices-afdd-siemens-5sv6016-6kk16

 
regards Mike

Re: AFDD (Regulation 421.1.7)

Posted by sdmoore on Apr 28, 2019 10:42 am

"The regs really say you must consider it and fit them if needed."

Do they really say that though?  The first sentence of the new regulation says that "AFDD's are recommended to provide additional protection against fire"

That use of the word "recommended" is surely saying that they should be used in all cases, unless there is a good reason not to do so.  Why would a designer not include a component that has been "recommended" by their own industry's regulations book?

I realise that the practicalities of my interpretation above lead to all sorts of problems of space, cost, arrangement of different manufacturer's devices etc.  I happen to think the regulation wording is clumsy and needs clarification from the IET pronto!  Without that clarification my own opinion is that we need to be allowing for these devices unless some other higher authority can give us the all-clear not to do so (e.g. fire brigade, building control, etc).

Stuart

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