Expanding Consumer Unit

Discussion in 'Electricians' Talk' started by Keenbutgreen, Jan 31, 2004.

  1. Keenbutgreen

    Keenbutgreen New Member

    I have a 100a Sentry Consumer unit with a 60a main switch and 7x MK RCB's with different circuits on them.
    I am just extending my bungalow and will need extra circuits for, shower, sockets, 30+ spots etc.

    My question is, what is the best way to expand the system?
    Can I add an extra CU being fed from main one?
    Do I have to get new unit with more fuses?
    Any suggestions would be welcome.

    thanks for your help.
    KBG
     
  2. Dicky Minton

    Dicky Minton New Member

    I think I would install a sparate Cu as you suggest. Buy one with a 30mA RCD as a main switch and move your existing ring main over to this new board and also use this new board to feed your new ring. The board can be fed by a single 63A MCB in the Sentry unit.

    Take the power feed for your new shower from this new board also. Make sure the breaker feeding this new board is installed right next to the main switch in the exisitng board.

    This way you sockets will be protected by an RCD (which is now a requirement of the regs) and your new shower is also protected by and RCD. This is the only way I can think of doing the job without ripping the old board off the wall and replacing it. This method does have the disadvantage that the sub-board is only rated at 63A (since that's the largest breaker you will get into the existing board) With a shower running at 40A the available load for the two rings is "only" 63-40=23A. You need to take a view on this, if you have say five people living in the house and the ring is feeding the kitchen it may be possible to overload it. If there are two people in the house, provided you havn't cleared B&Q of electric heaters, you should be O.K.

    You could install a new board and joint the tails into connector blocks, however, I don't like doing that because it leaves the installation with two main switches (one in each CU) which is not right. UNLESS you get the board in to install a 100A isolator for you BUT if you do that you may as well install a new consumer unit anyway.
     
  3. andyboy

    andyboy New Member

    if it were mine i would just replace it with a large split load unit. Although you can just add a smaller CU for your new extension, using a service connector block.
     
  4. Keenbutgreen

    Keenbutgreen New Member

    Thanks both for your replies.
    What is a split unit?
    what are the advantages of having a split unit.
    I already have a seperate isolator switch after the meter but before the CU if this helps.

    KBG
     
  5. Keenbutgreen

    Keenbutgreen New Member

    Do you suggest having a large enough unit to have all the seperate ciruits on one board?

    KBG
     
  6. sparkydude

    sparkydude New Member

    Hi
    a split load board as it is called basically has two sides to it, a main switch side and an RCD side, the RCD side affords earth leakage protection for circuits that might conceivably be used to supply equipment outdoors, or in high risk areas such as electric showers or sheds at the bottom of the garden Etc i would recommend a split load board such as the wylex ones that screwfix sell, as it would serve all your needs in one handy sized neat unit, instead of tails connectors,meter tails and all that extra stuff.

    Hope this helps

    any more questions feel free to ask or you can email me at NLASEN @ AOL.COM just remove the spaces

    cheers

    Nick
     
  7. Keenbutgreen

    Keenbutgreen New Member

    thanks very much, your reply has been a great help.
    So I can get one CU which has half the circuits protected by an RCD and the other half presumably are protected by RCB for individual circuits?
    Am I right in thinking that if a circuit on the RCD side has a fault the RCD will trip and all the circuits on the RCD side will go off together?

    What is the most number of circuits I can get on one split load CU?

    thanks
    KBG
     
  8. sparkydude

    sparkydude New Member

    Normally a split load board is 6+6 of esch although you can alter some boards by changing the busbar and cutting that to suit, but the most your likeley to need is going to be a 6+6 i would say, the rcd would trip all of the circuits connected to it yes, and the other side just has MCBs in it controlled by the main switch .

    If you need loads of ways then it might be worth going down the path of adding a new board beside it and makming one RCD and one Main switch but i doubt if you will need that many circuits in your bungalow

    Nick
     
  9. Keenbutgreen

    Keenbutgreen New Member

    Top Guy Sparky
    You have been really helpful
    I think a split CU with 6+6 will be ideal.
    I seem to get the impression from other posts that the best units to go for are either Sentry MK or Wylex.
    Would this be right?

    Thanks
    KBG
     
  10. ban-all-sheds

    ban-all-sheds New Member

    So I can get one CU which has half the circuits protected by an RCD and the other half presumably are protected by RCB for individual circuits?

    On both sides all the circuits have overcurrent protection provided by individual MCBs.


    Am I right in thinking that if a circuit on the RCD side has a fault the RCD will trip and all the circuits on the RCD side will go off together?

    If it's an earth fault, yes. If it's an overload fault, no.


    What is the most number of circuits I can get on one split load CU?

    MK go up to 21, but you can get a kit to link two together to make a 42-way.
     
  11. supersparky

    supersparky New Member

    ..BAS!!! you could always go for a TP-N bored?... me thinks that would be enough ]:)

    ss
     
  12. ban-all-sheds

    ban-all-sheds New Member

    Be good for lensman - he could have each individual socket in the house on its own dedicated RCBO....
     
  13. supersparky

    supersparky New Member

    PMSL bas!!!!

    ill keep quiet!

    ss
     

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