RCD Required?

Discussion in 'Electricians' Talk' started by Mickingreenfield, Mar 25, 2020.

  1. Mickingreenfield

    Mickingreenfield New Member

    I have just moved into to a house that was built 9 years ago. The house consumer unit has a RCD and one of the breakers covered is the supply to the standalone garage, fed with an armoured cable.

    The garage has a small consumer unit with a main switch isolator and two breakers. One for sockets and one for the garage lights and existing outside lights.

    I am in the process of adding additional outside lights and a water feature. Should I fit an additional RCD in the garage consumer unit, or is the one on the house sufficient?

    The RCD in the house consumer unit is a Legrand one with an 80 amp rating and a 30mA rating.

    Many thanks.
    techie likes this.
  2. Comlec

    Comlec Well-Known Member

    Photos of both consumer units please
  3. seneca

    seneca Screwfix Select

    As long as the garage supply is protected by the rcd in the consumer unit that's all that's required. Do check it though just in case the circuit breaker supplying the garage is on a non rcd part of the consumer unit.
  4. PandA3

    PandA3 Member

    The one in the house is fine.. they are all 30mA rating, so even if you put one in the garage it still wouldn't guarantee that it would trip before the house one so probably no point wasting your money.
    Your additional lights (if LED) and water feature are minimal loads, so add them to the Garage 6A (Lighting) circuit.
  5. dobbie

    dobbie Well-Known Member

    It would be better the garage being fed from a switch fuse, and have it's own rcd or preferably rcbo's in the garage unit. At the moment any garage fault can also trip the side of the consumer unit it is fed from in the house.
    nigel willson likes this.
  6. Mickingreenfield

    Mickingreenfield New Member

    Here house-unit.jpg they Are garage-unit.jpg
  7. Mickingreenfield

    Mickingreenfield New Member


    Thank you everyone for your replies. It is as I thought. The new lighting is all LED's so minimal loads.
  8. PandA3

    PandA3 Member

    Your set-up is fine and you will have no issues with just doing the job in hand using the 6A mcb.
    Your house CU is a split type, whereby the sockets and garage are the only circuits RCD protected, which is fine, but rules have changed for new installations since your house was built, so you will eventually end up at some point in the future having the entire House CU protected by the RCD. (Easy job on that CU for a spark.. 1 hour max) There's no requirement for existing installations to update to the new regs, so its your choice if and when to do it.
    Personally, I'd leave it as is. Nothing wrong, and at least all your lighting circuits will still be on if there is an earth fault in garage.
    Nothing wrong if someone recommends reconfiguring the CU and adding a switch-fuse to feed the garage and then changing the garage incomer to an RCD. But it is only a recommendation, so the choice is yours..
    If you have young kids in the house, then I would do the Main CU reconfigure (when things in the world return to normal) so that all the circuits were protected by the RCD.
    Good Luck
    P.S. Turn the 40A MCB to the Garage off before starting;)
  9. Mickingreenfield

    Mickingreenfield New Member

    That's great thank you very much for the prompt reply.
  10. Mickingreenfield

    Mickingreenfield New Member

    Just a thought, with my new lighting I will be running a new armoured cable to the location of flower bed which will be terminated in a suitable enclosure. From there I'm planning to install three spiked LED spotlights. Is there any opinion/rules on how long the flex can be from the box to the light fitting. I assume common sense needs to apply and keep the leads as short as possible. In my situation I have a bed where there will be three lights about 1.0m apart. So if I put the termination of the armoured cable in the middle I will have about 1.0m of flex from there to the light. Is that ok?
  11. Comlec

    Comlec Well-Known Member

    Wire your lights with suitable cable and all will be fine.

    Good luck with your project.

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