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Fuse Board to Consumer Unit?

Discussion in 'Electrics UK' started by dpm_dpmartin, 29 Aug 2015.

  1. dpm_dpmartin

    dpm_dpmartin

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    I will aim to do that. Haven't got one on my phone yet.
     
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  3. flameport

    flameport

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    It does if you want to comply with section 314.
     
  4. JohnW2

    JohnW2

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    In the sense that we've ben using plastic ones for decades, he's right. It depends to some extent whether you are planning to rent or sell the house; if the latter, a prospective buyer might well try to beat you down in price if, assuming it's after after Jan 1st, it then has a 'non-compliant' CU!
    Yes, as I and others said, that seems pretty likely.
    No, it certainly doesn't "need" them. There are some advantages, which you can discuss with your electrician, and the only real downside is cost. If you're going to rent the property, RCBOs might reduce the risk of you getting a 3am phone call about most of the house's electricity having died!

    Kind Regards, John
     
  5. JohnW2

    JohnW2

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    I'm not sure that a lot of people would agree with that, not the least becasue it would mean that most UK domestic installations were non-compliant with the regs. 314 is incredibly vague, and can probably be satisfied by having a couple of battery-operated (or battery backed-up) lights - and they would give 'protection' in the event of a power cut or service fuse blowing - something that no RCBO can do :)

    Kind Regards, John
     
  6. ericmark

    ericmark

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    As to consumer units the first question is what items it supplies are likely to have some leakage to earth. A standard RCD will trip at 15 mA to 30 mA and unless classed as high earth leakage on single item should leak more than 3 mA so in theroy 5 sockets could allow the RCD to trip with no fault. It is clearly not that bad, but 20 sockets on a RCD is reasonable 200 sockets are not and some where between two will be a point where in real terms we need to split into another RCD protected circuit.

    Using RCBO's which is a RCD and MCB combined will clearly remove any problems with unwanted tripping but also expensive. We also have the risk assessment where the stair well is lit form outside losing power does not cause a danger but if no outside light it does. Using emergency lights may be better than adding extra RCD's it is all down to that risk assessment.

    So as to selecting consumer unit first decide what is required. If two RCD's are enough then near any consumer unit will do. Over two then looking at either stacked consumer units with 4 RCD's or so many RCBO's and so many MCB's the latter the normal way to increase the number of RCD's.

    On to this we also have supply type TT is likely to trip RCD's more than TN and one has to consider neutral earth faults and should double pole RCBO's be used. Very few makes do double pole RCBO's of single module thickness so if double pole are required then the makes one can use is limited.

    Location is also to be considered. Both the house and items in the house. My mother has a distribution unit under the stairs. Moving to a new location will cost more but where it is it is impossible for my mother to reset any trip. She also has a kitchen only consumer unit which she can reset RCBO's with ease. Moving the consumer unit is not easy and really the only place even if not under stairs would cause the same problems if not greater than where it is as a fire in new location would stop both stairs and front door being used in the event of a fire in the consumer unit.

    It really does not matter if Wilex,LAP, or any other make what is much more important is does the manufacturer make one which suits the house you have. Once you know what you need then to say I need a X way consumer unit with Y MCB's Z RCD's and U RCBO's with single or double pole switching for use with a TT/TN-S/TN-C-S supply then you can look are what makes there are which fill your requirements.

    A caravan or boat will often only have one RCD covering all as it's so small. A 6 bedroom house will likely need at least 4 to stop unwanted tripping. Remember caravans and boats have battery backed lights.

    I once was asked at work about what a guy should do in his house and I assumed a standard 3 bedroom house with TN-C-S supply and gave a reasonable answer. However latter I visited and his house consisted of many buildings all joined together and my answer was completely inappropriate to his special circumstances. I would assume cellar means large house as such really we do need some idea as to how large.

    I went to a farm house in mid Wales with a drive between what looked like a garage and the house. The garage was in fact a generator building which supplied DC power to charge a bank of 2 volt lead acid glass batteries in the house cellar which in turn powered a rotatory converter which supplied the three stories plus servants quarters including all the call indicators and bells. This lay redundant when the national grid reached the house and the whole lot was then feed with a split phase supply. There were wires everywhere old and new extra low voltage and low voltage AC and DC and any one not knowing the history would really have a problem working out what fed what. For all we know you may have a similar house.

    You are asking questions but giving no answers so I would say start again and explain exactly what you have. How many lighting circuits, how many ring finals, does it have electric shower, oven, hob, what type of heating and the list goes on. Once we have a picture of what you have then maybe we can give answers.

    But if it were me first step would be to employ an electrician to complete an EICR which should answer most the questions needed to make reasonable recommendations as to what is required.
     
  7. dpm_dpmartin

    dpm_dpmartin

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    Thanks again.

    The house is intended for sale. If it cannot be sold it will be let as a backup... so the refurbishment does need to be mindful of both outcomes.

    I genuinely have no idea if I want to comply with Section 314 or not. I suppose I should want to... :sneaky: ...seriously, though, I always do things by the book with rental property, and this will be no different...

    I've learned a lot today.
     
  8. dpm_dpmartin

    dpm_dpmartin

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    Got it, please bear in mind my first entry to this thread - I am buying a house to do up. Offer made, offer accepted, house off the market, conveyancing is still to do.. so, while the Vendor was happy for me to walk around it yesterday and take a couple of photos that I thought would be helpful to me, I don't yet have full access to come and go as I please.

    And, in all honesty, I think I've got a lot from this... I know that the picture I provided shows some things that people have said are a bit odd, I know that I need to understand more about the meter and the incomer (or an Electrician does), I know I definitely need a new Consumer Unit and I should at least consider a metal one to be fully compliant from 2016 onwards - I know the ballpark for this will be £350, I know the house may or may not need a rewire - but only an Electrician can tell me that for sure and that might be best achieved by commissioning a report, I know that most households in the UK don't have Consumer Units with RCBOs.
     
  9. flameport

    flameport

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    Lights are mentioned, but are not relevant to the highlighted parts below.

    With dual RCDs, a single fault results in multiple circuits being disconnected, causing significant inconvenience.


    314.png
     
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  11. JohnW2

    JohnW2

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    "Minimize inconvenience" [why do the spell in American?] is about as vague as it could get, so there will be a vast range of interpretations of (i) - but when the subject is discussed here, the main 'inconvenience' (and potential danger) usually mentioned is of a house being "plunged into darkness" by a fault on some other circuit. At the other extreme, some may regard it as 'inconvenient' having all the sockets on a final circuit dying as a result of a single fault, so even your RCBOs might be non-compliant in their eyes!

    As for 314.2, that is talking about "parts of the installation which need to be separately controlled", and I'm not even sure what that means in relation to most domestic installations.
    Do you really believe that the majority of UK domestic installations are non-compliant with BS7671 (for this reason)? As I implied, one can even argue that there are ways to make a single RCD (covering all circuits) setup compliant with 314, but the great majority appear to be happy that a dual-RCD CU does comply. I'd be interested to hear others' views about this!

    Kind Regards, John
     
  12. JohnW2

    JohnW2

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    Damn - quoted instead of edited - again!
     
  13. JohnW2

    JohnW2

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    Why? Are you suggesting that, in a TN installation, the MCB is likely to trip before an RCD/RCBO does, or what?
    One doesn't really have to consider DP RCBOs if all final circuits are RCD- or RCBO- protected. The problem with TT only arises if there are some unprotected final circuits, such that an up-front Type S RCD has to be installed. If all circuits are RCD/RCBO-protected, that is not necessary.

    Kind Regards, John
     
  14. EFLImpudence

    EFLImpudence

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    Minimising inconvenience.

    There has just been a(n almost heated) discussion in another place regarding this subject but without conclusion.

    It obviously depends on how you define minimise.
    Whether it is the absolute minimum that could ever be designed or the minimum with the equipment that is available.

    As it is not possible to force things on the customer which they do not want to pay for, I would say the latter.
     
  15. JohnW2

    JohnW2

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    ... and also on how you (or the occupant of the premises in question) define "inconvenience". As I said, one person might regarded it as 'inconvenient' that all sockets on one circuit dies because of one fault, whereas another person might not regard themselves as being particularly 'inconvenienced' by loosing most of their electricity (or all of their lighting)!

    I may be wrong, but I really don't think many electricians would regard a dual-RCD CU as being non-compliant with 314 - do you?

    Kind Regards, John
     
  16. EFLImpudence

    EFLImpudence

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    No.
     
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  17. ericmark

    ericmark

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    I would advise when you get the pictures start again with new thread as by that time this one will be so big people will not look at it. I had thought you had the house not waiting to get it so clearly now you will not be able to post pictures. You could indicate how big it is however.

    As seen the big question is money to inconvenience ratio. Until 2008 we did not protect all circuits with an RCD and there has been since 2008 much talk about division of installation where RCD's are concerned. A empty house is unlikely to have a RCD trip even if only one fitted for whole of house. Only as appliances are brought into the house will any problems arise. So an electrician wiring a house often has no idea what will be fitted. Best he can do is guess based on other houses he has wired before. There are problem areas most IT equipment did have filters which would have a small earth leakage which could build up over the house causing problems. It seems modern appliances tend not to use earth as much for their filters so age of equipment does have a bearing on earth leakage. Electric ovens, hobs, and cookers were a big problem but today it seems this has been over come.

    The high integrity consumer unit allows a mixture of RCD with MCB and RCBO to be used so vulnerable circuits can have their own RCD protection. If sockets are on RCBO then much of the tripping problem is removed, having the cooker on RCBO may also help. Lighting does not tend to have earth leakage so no real need to put on it's own RCBO. The splitting can go either way, either put important items like lighting and refrigeration supplies on RCBO so a general trip will not effect them or put items likely to cause trips on RCBO so if they trip it will not effect the rest.

    There is no hard and fast rule and really this is up to the owner however hard for the electrician to explain the options v price and often the electrician makes the choice.
     
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