Consumer unit tails question

Discussion in 'Electricians' Talk' started by dwain pipe, Apr 4, 2016.

  1. dwain pipe

    dwain pipe New Member

    Hi all,

    My wife's about to start renting a property to which she'll be moving her business very shortly. It's a large wooden cabin. Inside the cabin there is a small-ish metal box containing a 100A isolator and a 30mA RCCB. The box is fed from outside the building via an armoured cable, size unknown at this point in time but it's metered and isolated elsewhere on the premises. The metal box feeds an adjacent consumer unit via a pair of thick tails, much thicker than the SWA cable that feeds the building. This second consumer unit contains a 100A isolator, and the various MCB's for the lighting and sockets etc.

    Sorry that's a bit wordy, but my first question is will there be a problem with the tails between the 2 consumer units being thicker than the SWA that's feeding the building?


    Attached Files:

  2. nffc

    nffc Active Member

    As long as the over current protective device is suitably rated for the smaller cable then all is fine.

    It looks like a 10mm SWA. What is the rating of the fuse/MCB that the SWA cable is connected to?
  3. dwain pipe

    dwain pipe New Member

    Hi, the RCCB in the metal consumer unit says 63A 30mA on it if that's what you meant. If you mean what's on the other end of the SWA cable, it's in another building and we have no access to have a look at it but that's where the electric meter is. Thanks.
  4. nffc

    nffc Active Member

    Yes it is the other end that is important.
  5. dwain pipe

    dwain pipe New Member

    Thanks nffc. I will try to find out. I'm just in the process of asking the owners of the property whether they can have an electrician inspect the cable, make sure it's fit for purpose, and replace it if necessary/possible with a bigger one. It'll be running an electric shower (7.5KW installed in the building at present but hopefully a larger one at some point), some led downlighting (mains), 1 or 2 fluorescent strips, and a dog drying cabinet (don't know without looking what that draws but it heats up and there's a large fan inside).
  6. peter palmer

    peter palmer Super Member

    Seems a lot of work to get a supply to the cabin, why not fit the RCD as the main switch in the consumer unit and take the armoured straight into the CU. That is a Curve board from Denmans, quite sturdy units and would certainly take a 25mm armoured gland.

    Also it looks like the metal box is right above the consumer unit so even fit a 100mm metal box above and take the armoured cores straight through. Must have been on day work.
  7. dwain pipe

    dwain pipe New Member

    I believe the cabin was formerly used by a company who sold solar panels etc. The cabin is fitted with underfloor heating but this is no longer used (pump and heater both removed, underfloor pipes capped off). There is evidence that a PV inverter was once installed in the cupboard where the consumer units are. That might account for why there's a bit more kit installed than might be expected for a simple cabin.

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