Discuss When to install metal consumer units in the Electrical Forum area at ElectrciansForums.co.uk.

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  1. alex kane
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    alex kane Active EF Member

    Hi Everyone

    I am aware that we now have to install metal consumer units in domestic premises now but at what point should we swap a plastic board over to a metal one?

    The reason I ask is I've been to plenty of jobs where there is a plastic CU with no RCD protection. Ideally I would swap the main switch for an RCD but should I also be swapping over the whole CU for a metal one?

    What work/ at what point do you say to the customer "you need a new CU" besides when the job is to install a new one obviously? I know I could write a note on my EIC but personally I'd rather not have to do that.
     
  2. Flanders
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    Flanders Regular EF Member

    Location:
    Tamworth
    Not sure I would ever just change a main switch with a RCD Unless required for a TT supply.
    The only reason that I could see a domestic installation needing upgrading to RCD protection to make the installation safe would be for socket outlet liable to be used outdoors and you could fit an RCBO or RCD sockets for that.
     
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  3. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    Do you think swapping a main switch for an RCD complies with the regs?
     
  4. Midwest
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    Midwest Electrician's Arms

    Location:
    Oxfordshire
    Don't thing the spirit of 421.1.201 requires any replacement of plastic to metal, regardless of how much the inners you replace. That would just be maintenance.

    If you replaced the CU because of lack of replacement parts, then that would be the time to apply the reg.

    Someone recently posted about moving a CU, i.e. to one side a few inches. That was a lively debate :)
     
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  5. static zap
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    static zap Regular EF Member

    Location:
    west midlands
    (RCD - for Main switch )...

    The disadvantage is being in the dark , actually !
     
  6. alex kane
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    alex kane Active EF Member

    RCCB's that meet BS EN 61008 are rated for isolation so I don't see the problem? I know on a big installation this wouldn't be ideal but say on a CU with four circuits.
     
  7. Ian1981
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    Ian1981 Regular EF Member

    Location:
    North east
    In what context do you require a rcd main switch to replace a main switch isolator?
    I.e. What job are you undertaking that requires it?
     
  8. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    ^^ best you review 314 in the BYB
     
  9. Risteard
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    Risteard Electrician's Arms

    Location:
    Derry, Ireland
    Business Name:
    Walsh Electrical Services
    I would suggest that it can depending on the circumstances. It's certainly not expressly forbidden. A risk assessment would determine whether inconvenience caused was excessive or presented any danger. As someone else mentioned maybe there are only a handful of circuits fed from the DB with other DBs present. Otherwise we would outlaw all instances of using an RCCB to protect more than one circuit which would be a nonsense!
     
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  10. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    ^^ I only raised this as lots of people don't seem to realise that this reg even exists... there are, of course lots of RCBO options .....
     
  11. alex kane
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    alex kane Active EF Member

    The reason I ask this question is because most customers won't pay for RCBO's even when I've explained it's the best option because of the cost. If I'm to do work in their house I need to ensure it's RCD protected to cover my back. Swapping the main switch for an RCD is the quickest/ most cost effective way to do this.

    I suppose installing one RCBO for the circuit I've worked on would suffice but it would be better to ensure the whole property has RCD protection. This scenario is where I wasn't sure whether I would have to change the CU to a metal one.

    Which reg specifically says you cannot use an RCD as a main switch?
     
  12. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    Corrected that for you

    You are obviously new to the game ... a RCBO is more than adequate AND then you only need to test / inspect your circuit - install an upfront RCD means you need to test the entire installation too.

    As for changing a CU to AMD3 for a new circuit or circuit change - this is NOT the case, and anyone saying this is not being honest.
     
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  13. Ian1981
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    Ian1981 Regular EF Member

    Location:
    North east
    If you are working on multiple circuits which, by the work that has been undertaken require rcd protection ( installed extra sockets, installed new wiring into a bathroom) then if no rcd protection exists to the installation, the client should be notified of what the new works will entail and what requirements/ changes are needed to the installation/consumer unit before work is undertaken.
    Individual rcbo s are an option if the existing consumer unit can accommodate.
    The consumer unit if changed to allow the multiple circuits worked on rcd protection would then require to be constructed of a non-combustible material ( ferrous)
    Installing an upfront rcd protecting the whole installation is generally regarded as poor practice and offers no division of circuits for safety purposes think the regulation has been quoted 314 etc.
    One faulty circuit may cause the full installation to disconnect which is a nuisance if anything and highly inconvenient.
    If it was an acceptable method the dual rcd consumer units would be irrelevant.
    Hope this helps.
     
    Last edited: Apr 19, 2017
  14. alex kane
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    alex kane Active EF Member

    I understand it's not always good practice but getting people to pay for a new board/ RCBO's isn't always easy. On small boards with 4 circuits or less I don't see this being too much of a problem. A split load 20 way board would have 10 circuits on 1 RCD each. I don't hear people moaning about that.

    I always tell my customers if they need an upgrade. Testing the whole installation is a minor inconvenience to me when we're talking about a safety issue.

    All I wanted to know was whether installing an RCD as a main switch was possible and whether the board would require changing.

    I think it's obvious from Murdoch's comments he doesn't know a much as he lets on and just likes slamming others comments.

    You're never too old to learn
     
  15. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    Matey ... if you have a house with a 4 way CU or a 20 way CU, adding a single up front RCD will deliver the same result when a fault occurs - EVERYTHING will switch off...

    A RCBO will cost less that a RCD and testing ALL the other circuits...... what is there not to understand?
     
  16. Ian1981
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    Ian1981 Regular EF Member

    Location:
    North east
    must be a massive house to be a 20way db.
    The other way to look at that is at least 10 circuits are still functional.
    It's just an option tho it's ultimately up to the installer to decide and verify his work against bs 7671.
    Just out of interest if it's an existing split load board with one side of the db non rcd protected and one side protected by an rcd do you still replace the main switch with a rcd and have one 30mA rcd upstream to another 30mA rcd?
    as that would be kinda pointless.
     
    Last edited: Apr 19, 2017
  17. R G
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    R G Electrician's Arms

    Location:
    Norfolk
    I find it surprising that anyone would do what you are doing in order to satisfy the client in way of costs , surely the fact that a complete test of the whole property and correcting any faults and the cost of the RCD and the fact that there may well be faulty appliances within the property would be far from what the client would really want
     
    • Agree Agree x 1
  18. spinlondon
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    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    It would not comply with 314.1(i), 314.1(iv) and 314.2.
    You would increase inconvenience in the event of a fault 314.1(i).
    You would increase the possibility of unwanted tripping of the RCD due to excessive protective conductor (PE) currents not due to a fault 314.1(iv).
    Circuits would now be affected by faults on other circuits 314.2.
     
    • Agree Agree x 1
  19. Flanders
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    Flanders Regular EF Member

    Location:
    Tamworth
    I beleave there is guidance that you can add a circuit to a plastic consumer as long as checks have been carried out , so your question on replacing the main switch with an main rcd would work on the same principle, the reason i would not fit an upfront rcd is because of the reasons others have said , even if a house as 1 light circuit and 1 socket I would want them protected by separate rcds/RCBOs , so for example if you had 1 main rcd , a lamp blows and so trips both the circuits , the home owner can not reset the rcd for what ever reason so no power, were as if there where seperate Rcbos , the home owners would still have the sockets so could plug a stand lamp in and would not loose a freazer full of food:)
     
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  20. charlie76
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    charlie76 Regular EF Member

    Location:
    Notts
    Business Name:
    CES Midlands
    On your cert "Comments on existing installation....." just note down that the consumer unit is not in line with regulation 421.1.201 you have commented on it, you didn't install it, you can't do any more. If you really want to cover yourself, write a letter to the client advising it should be upgraded to an AM3 board when you send your certificate. Job Done.

    You may "rather not have to" write on your cert but your client may "rather not have to" shell out for a new consumer unit just because you are adding a new socket for them. You've got to be sensible, if it was a new install or a rewire, then include a new board, if its £100 for a new socket install, is your customer going to shell out £400 for a new socket and a new board and a load of testing. Nope, you loose the job and the next man gets it and he will the comment on his cert that you would "rather not have to".

    If there is no RCD protection, install an RCBO or even an RCD fused spur.
     
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