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Discuss Does this comply with 314? in the Electrical Forum area at ElectrciansForums.co.uk.

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  1. Murdoch
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    Murdoch Electrician's Arms

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    Woking
    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 :

    Kate CU.jpg

    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?
     
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  2. Bob Geldoff1234
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    Bob Geldoff1234 Regular EF Member

    I would say you are being very picky here.It only feeds the loft so the rest of the house must be on separate circuits.If you argument stood up then dual RCD boards would have to be banned.
     
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  3. Murdoch
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    Murdoch Electrician's Arms

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    Why?
     
  4. Bob Geldoff1234
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    Bob Geldoff1234 Regular EF Member

    Because your saying that if the RCD trips then the power and lighting circuits will go off in the loft.Going on that principle then when a dual RCD board trips one of its RCD's then 4-5 circuits go off.Obviously this practice is still accepted as being ok otherwise the powers that be will have told us to fit RCBO's to everything as standard.
     
  5. Murdoch
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    Murdoch Electrician's Arms

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    Woking
    ^^ but with a dual board you would endeavor to avoid having the lights and sockets for the same room on the same RCD.

    My 2nd example is more obvious - and no it wasn't TT!

    I stopped fitting dual boards when the AMD3 boards were forced on us - RCBO's every time now!
     
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  6. Phil Thompson
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    Phil Thompson Let us light up your life! Electrician's Arms

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    But is it not that you put downstairs lights on the RCD with the upstairs sockets and visa versa. Enabling that if a trip fault occurs on 1 Circuit you still have lighting ability via the sockets in that area coming from the other RCD, which voids the dual RCD argument.
     
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  7. Phil Thompson
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    Phil Thompson Let us light up your life! Electrician's Arms

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  8. uksrevivor
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    uksrevivor Trainee Access

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    South Wales
    I hope thats not your safe isolation Murdoch lol
     
  9. Murdoch
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    Murdoch Electrician's Arms

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    Woking
    What I was doing was in the main house - so not my "safe isolation".

    FWIW the "other" CU was an older MK - with a 30Ma main switch!

    If it was me I would have taken one of the other lighting circuits out of the old board and put it in the new board, then placed the new lighting circuit in the old board!
     
  10. uksrevivor
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    uksrevivor Trainee Access

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    I was taking mick m8 lol im still training and learning.
    But agree on the point of rcbo's as it was a new loft conversion so wouldn't of cost much. Im not to keen on the fact if a fault occurs they will loose both circuits in the loft so I would of either separated them or fitted rcbo's
     
  11. HandySparks
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    HandySparks Trusted Advisor

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    Neish Electrical Services
    OK, I agree that RCBOs all round is 'best' and minimising inconvenience is a good thing. However, I think that the problem of being plunged into darkness is over-stated. Where I am, you're much more likely to have a power cut than an RCD trip. So, if darkness was a major safety issue, we would be installing emergency lighting to all rooms in domestic premises.
     
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  12. Risteard
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    Risteard Electrician's Arms

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    Walsh Electrical Services
    Complete non-issue.
     
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  13. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

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    Green/yellow tape provides better safe isolation.
     
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  14. Murdoch
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    Murdoch Electrician's Arms

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    Woking
    Why?
     
  15. Risteard
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    Risteard Electrician's Arms

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    Derry, Ireland
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    Walsh Electrical Services
    Because unless you are going to argue that the Regulation requires every circuit to be individually RCD protected then it doesn't hold water. And that certainly isn't what is demanded by BS7671. Minimising inconvenience is a matter for a risk assessment - nowhere is it suggested that all possible inconvenience must be eradicated. So whilst you are entitled to your own interpretation of the Regulation I wouldn't agree with such an interpretation. If that's what JPEL/64 had wanted then presumably that's what they would have written.
     
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  16. Davisonp
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    Davisonp Regular EF Member

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    Amersham
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    Absolutely All Electrical LTD
    Is the “Other CU” with RCD as main switch supplying the new loft cu? No discrimination if that is the case?
     
  17. diditrain
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    diditrain Electrician's Arms

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    north west
    How much of the 45k, did the Electrician see though?
     
  18. Midwest
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    Midwest Electrician's Arms

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    Oxfordshire
    If I was doing the installation for the loft conversion, I would of considered 314 and installed RCBO's.

    In this install, if the RCD trips, and the occupier gets up in the middle of the night to investigate and trips over his bed pan, 'cos he's got no bed side light or room light, the installer has not done all he/she can to 'avoid danger & minimise inconvenience etc'.

    So I agree with Murdoch IMO.
     
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  19. Murdoch
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    Murdoch Electrician's Arms

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    Woking
    Split tails and Henley block
     
  20. wirepuller
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    wirepuller Trusted Advisor

    Location:
    south uk
    As already stated it's a non issue.
    If the end user loses the loft conversion electrics he can run a lead from elsewhere until it's fixed. If it's just nuisance tripped then the rest of the house is still on so he can see to reset.
     
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  21. Murdoch
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    Murdoch Electrician's Arms

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    Woking
    I disagree .........IMHO the designer of the loft conversion circuits has failed to comply with the regs......
     
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  22. Murdoch
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    Murdoch Electrician's Arms

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    At a guess, maybe around £900
     
  23. Midwest
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    Midwest Electrician's Arms

    Location:
    Oxfordshire
    Not easily done in the middle of the night, or if your elderly or infirmed or just a little bit squiffy. Not really a good design, if you have to faff around with extension leads (not everyone has one), when a couple of RCBO's is a simple but easy fix?
     
  24. wirepuller
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    wirepuller Trusted Advisor

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    south uk
    You are of course entitled to take that view.....but really your objection makes no sense. If it was installed on 2x RCBO's and the lighting one tripped during the night, and your elderly /infirm/squiffy type does not have a light plugged in or cant reach it then your RCBO has not improved their safety one bit.....Of course RCBO's are always preferable but to suggest this is non compliant with just two circuits on a separate RCD and the rest of the house unaffected is incorrect IMO.
    A job I did last week involved 4 new circuits for kitchen equipment which I supplied from a 4 way DB with an RCD main switch, the rest of the existing installation is split over two RCD's on the existing DB. I have an NICEIC visit next month and he'll probably see this job. I'll let you know if he pulls it up as non compliant.
     
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  25. Midwest
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    Midwest Electrician's Arms

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    Oxfordshire

    Well, I seem to recall someone on this forum arguing that a dual RCD set up, was non compliance with 314. I think that's a bit extreme. What someone does with an installation after you've installed it, you have no control over. But in the example given here, at least having two separate RCBO's would give some scope.

    In the example you've given, a loss of complete power to a kitchen, is unlikely to cause danger as suggested in 314, although it may well cause inconvenience. However, the control of both lighting & power for a bedroom at night by one RCD, could cause danger, dependant on the end user (when I designed this, did I do all that was reasonably practicable).

    You may be aware that the draft for the 18th, will make more demand of the designer to consider unwanted tripping, (proposed) reg 531.3.2. Limiting down stream current to 30% of the RCD rating. So perhaps you kitchen design may not comply with the 18th?
     
  26. spinlondon
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    spinlondon Trusted Advisor

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    Harlow Essex
    Assuming it's a new build, it complies.
    Could have been done better.
     
  27. Murdoch
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    Murdoch Electrician's Arms

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    Woking
    Not a new build. Loft conversion
     
  28. spinlondon
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    spinlondon Trusted Advisor

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    Harlow Essex
    New build as in new room in the loft.
    Or are you saying the loft was already converted?
     
  29. wirepuller
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    wirepuller Trusted Advisor

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    south uk
    I am not aware of those proposals, are you saying it is proposed that a 63a RCD would be restricted to a load of 21a?.....then presumably a 32a RCBO would be restricted to under 11a?
    So a 10kw shower would need a minimum 135a RCBO ?....Sorry if I'm having a blonde moment but that just doesn't make any sense.
     
    Last edited: Aug 19, 2017
  30. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

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    Not sure if this will be legible but here it what it states. 20170819_160512.jpg
     
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  31. Rpa07
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    Rpa07 2000 posts - only 46379 behind Telectrix! Electrician's Arms

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    That's surely relating to the residual earth leakage current, no? So they are saying that if you have appliances that have a heavy leakage then a 100ma RCD will have to be provided up from 30ma or division of leakages attempted?
     
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  32. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

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    Correct, the accumulated leakage of upstream circuit/s from an rcd should not exceed 30% of the rcds rated residual current. So for an rcbo it applies to the connected circuit, for a dual rcd board the accumulated conductor current and/or leakage applies to the sum of circuits protected by each rcd. So for 30ma that is 9ma if my math is correct.
     
  33. Rpa07
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    Rpa07 2000 posts - only 46379 behind Telectrix! Electrician's Arms

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    I sense RCBOs in all our futures - @Murdoch@Murdoch is like a prophet, like!
     
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  34. Midwest
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    Midwest Electrician's Arms

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    Oxfordshire
    Nope, I think the suggestion is the designer must divide the circuits across RCD's, so that any anticipated earth leakage would be limited to 30% of the tripping current for the RCD, i.e. 10mA for 30mA RCD. So consideration of the appliances and loads connected to said RCD. Kitchen appliances and IT equipment come to mind.

    Westy proceeds me. See why its important to read & comment on the draft. You've got 3 days left.
     
  35. Rpa07
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    Rpa07 2000 posts - only 46379 behind Telectrix! Electrician's Arms

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    So RCBO boards would effectively negate leakage from other areas on other circuits -
    Your kitchen leakage would be on that RCBO and your IT leakage on the downstairs ring or radial.
     
  36. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    With rcbos you will not get accumulated currents from other circuits but rcbos are lawless things. It suggests correct division of circuits to avoid unwanted tripping so for example if you install a ring final circuit with ten points of utilization is there a likelihood accumulated leakage currents of connected appliances may cause unwanted tripping, if yes then two ring final circuits with five on each may be a better option.
     
  37. wirepuller
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    wirepuller Trusted Advisor

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    south uk
    That makes more sense. It would not be an unreasonable proposal to design a low potential earth leakage into an RCD protected circuit.
    Cue amended forms and earth leakage measurements on all RCD protected circuits.
     
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  38. Rpa07
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    Rpa07 2000 posts - only 46379 behind Telectrix! Electrician's Arms

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    Let's hope the prices of earth leakage clampmeters come down then - otherwise the results will be as fictional as the BS7671 is now!
     
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  39. Midwest
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    Midwest Electrician's Arms

    Location:
    Oxfordshire
    I clamped my own house the other day. PC running, few led lights on, tv on, appliance turned on but not running. Clamp meter's a cheap en, but I had 14mA leakage. But I've have that split across RCD & RCBO's. Went to a job in the afternoon, semi with 1 x lighting, 1 x RFC & electric cooker. 9mA eath leakage.
     
  40. Midwest
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    Midwest Electrician's Arms

    Location:
    Oxfordshire
    That's my pleasure, glad I've pointed it out to you :)
     
  41. Midwest
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    Midwest Electrician's Arms

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    Oxfordshire
    So now what do you think of Murdoch's original post?
     
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  42. Murdoch
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    Murdoch Electrician's Arms

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    Woking
    So if we can just slap in single up front RCD boards, what is the point of the reg in question AND why did we all start putting in dual RCD boards

    Just wondering ?
     
  43. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    Was a loft, now 2 rooms
     
  44. Paignton pete
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    Paignton pete Regular EF Member

    Location:
    Over the rainbow
    I thought it was 25% so 7.5mA.
    I haven't got regs book in front of me so I may be wrong
     
  45. spinlondon
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    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    Did the loft originally have sockets and lights?
    Were they on separate circuits?
    Were the separate circuits protected by a single RCD?
     
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