External Lighting: Feeding a 3A FCU from 13A FCU.

Discussion in 'Electricians' Talk' started by JMJacks94, Dec 27, 2020.

  1. JMJacks94

    JMJacks94 New Member

    I am trying to add a 10W LED PIR external light to my rear wall.

    This is the current setup:

    (RFC 13A FCU) -> (2Gang Spur for fridge and microwave). The spur is not normally accessible hence the switched FCU.

    Can I do any of the following and maintain compliance with the regs?

    My preferred plan:
    Connect in an external IP54+ 3A FCU via the (feed or switch?) @ 13A FCU with appropriate cable (1.5 or 2.5?), and then connect the light with appropriate lighting flex (0.75, 1 or 1.5?)

    Second plan:
    Connect in a IP54+ 3A FCU via the 2gang spur with appropriate cable (1.5 or 2.5?), and then connect the light with appropriate lighting flex (0.75, 1 or 1.5?)

    Many thanks in advance.
  2. Teki

    Teki Screwfix Select

    It's probably not a good idea to have any external lighting on the same circuit as the fridge. If water maanges to find its way into the light fitting/PIR, it will trip any RCD upstream and take out the fridge as well.

    If the external light is 'cheap' one, then there is more chance of this occurring.
  3. JMJacks94

    JMJacks94 New Member

    Very good point - thanks, noted!

    Ignoring the current use of the circuit, is the type of alteration I am suggesting compliant?
  4. JMJacks94

    JMJacks94 New Member


    Is anyone able to advise on the above?

  5. CeSparky1

    CeSparky1 Active Member

    You cant connect to the feed side of the FCU or that would be a spur off a spur, you could connect to the load side of the fcu or you could come off the socket. You can only Spur once however if you spur via a FCU you can then spur off as many times as you want (Obviously if you put to much load then the fuse will keep blowing).

    As for RCD, it will make no difference unless you have a separate RCBO just for the external light but nobody does that. Its a good idea to have a fcu so if water does get in to the light it can be isolated from the rest of the circuit and then the RCD can be reset and the light sorted when its not raining. My only suggestion would be have the fcu on the inside as if water gets into the fcu and trips the RCD then you cant isolate that unless you also isolate the fridge and microwave.

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