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Lights Supplied by 30 Amp Ring Final. B.S. 3036 Fuse.

Zoomup
HellOOOoooo All,


I came across a strange one today. I went to change a faulty touch dimmer switch for an ordinary light switch. I discovered that the two lights controlled by the switch did not originate at the lighting circuit, but from a 30 Amp wire fused ring final. The supply was connected to an old metal double socket box below the light switch, in an added conservatory, with a blank plate over it. I can not add a fused connection unit as the box is a double socket box. The blank plate is covered by a small easily removed panel convector heater. I was considering installing an inline fuse holder in the double socket box for the lighting circuit. The lamps are low energy types so overloading is very unlikely, but faults may occur.


Thoughts please.


Z.
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    I can not add a fused connection unit as the box is a double socket box

    There are plenty of "modular" systems that'll allow you to make up a FCU on 2G faceplace (even if you'd need an extra blank or two) - either conventional grid modules or some of those that fit into Euro plates.


    Presumably the lighting is wired in something smaller than 2.5mm² and/or the lights themselves aren't suitable for 30A protection (e.g. BC or ES lampholders - 559.5.1.204).


      - Andy.
  • 0
    Can you fit a   (Grid style fuse holder ) and a (grid style blank or two ) in a (grid double box sized blank plate )

    Other makers offerings may be preferred  (examples)


    Or, is the new light switch full size - an FCU with a switch may be a possible, or a grid combo of  fuse and switch .

    At the shallow end, you could fit a double socket and plug the lights in I suppose...?

    The only real risk is if a catastrophic failure of the lights occurs so a 13A fuse would be OK.

    M.

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    Thanks. Oh yes, I had forgotten about the double size plate grid systems. I am out of touch. (The lighting is wired in 1.0mm2 T&E.)  Having said that I do use a smaller grid system on a single plate for fusing down extractor fans to 3 Amp for permanent L and 3 Amp for trigger L.


    "Presumably the lighting is wired in something smaller than 2.5mm² and/or the lights themselves aren't suitable for 30A protection (e.g. BC or ES lampholders - 559.5.1.204)."                       Yes Andy  there are two B.C. lampholders.



    Z.
  • 0
    for fusing down extractor fans to 3 Amp for permanent L and 3 Amp for trigger L

    Does that make (in BS 7671 terms) two distinct circuits with a shared N?

       - Andy.
  • 0
    AJJewsbury:
    for fusing down extractor fans to 3 Amp for permanent L and 3 Amp for trigger L

    Does that make (in BS 7671 terms) two distinct circuits with a shared N?

       - Andy.


    Dunno about that, but it does follow the manufacturer's instructions about fusing the extractor fan at 3 Amp. This is required if the lighting supply which feeds the light switch triggered timer fan is protected by a 6 or10 Amp M.C.B.


    Z.


  • 0
    If the double socket is behind a radiator it might be missed by someone else if the fuse blew.

    you could fit an fcu at the light switch with front cable exit (possibly flat plate), then a stand off frame, then the touch controller replacement.

    Your 2x3A fuse arrangement might need a 2 sources of supply label in the fan.
  • 0
    Zoomup:
    AJJewsbury:
    for fusing down extractor fans to 3 Amp for permanent L and 3 Amp for trigger L

    Does that make (in BS 7671 terms) two distinct circuits with a shared N?

       - Andy.


    Dunno about that, but it does follow the manufacturer's instructions about fusing the extractor fan at 3 Amp. This is required if the lighting supply which feeds the light switch triggered timer fan is protected by a 6 or10 Amp M.C.B.


    Z.




    Do the instructions really ask for two separate fuses? I thought the usual solution was to fuse down before the light, so feeding the light and L and SL to the fan with a single fuse. Two fuses with a common N would seem to technically be a contravention of 521.8.2.


      - Andy.


  • 0
     

    Do the instructions really ask for two separate fuses? I thought the usual solution was to fuse down before the light, so feeding the light and L and SL to the fan with a single fuse. Two fuses with a common N would seem to technically be a contravention of 521.8.2.


      -




    It is not always possible to easily fuse down before a bathroom or shower room light. I thought that your previous question was about to trick me. 521.8.2 does not apply, as I am only dealing with ONE final circuit, that of the lighting circuit feeding a single timer extractor fan.  No probs. here.


    Z.


  • 0
    OlympusMons:

    If the double socket is behind a radiator it might be missed by someone else if the fuse blew.

    you could fit an fcu at the light switch with front cable exit (possibly flat plate), then a stand off frame, then the touch controller replacement.

    Your 2x3A fuse arrangement might need a 2 sources of supply label in the fan.


    The blanked off double socket BOX is behind a small easily removable convector heater. The fuse could be missed but is the lesser of two evils. The circuit can not be overloaded as it only serves  two ceiling lights. The fuse would be there to protect from serious faults like rodent damage or nail bashing through cable.

    No; F.C.U. with flex outlet that you suggest would not be acceptable to the wife of the house. The single light switch is much neater.


    All common timer fans have a Permanent L and a switched trigger L. This is common knowledge. The manufacturers do not supply such a label so obviously consider it unnecessary.


    Z.


  • 0
    Official extractor timer fan instructions....


    Electrical 220-240V - AC. 50Hz Single Phase consuming 7 Watts. These fans are double insulated and do not require an earth. All wiring must comply with current IEE regulations. A double pole isolating switch, having a contact separation of at least 3mm in all poles, must be used with a 3 amp fuse fitted. The fan must not be accessible to a person using either the shower or bath and mounted a minimum of 1.8 metres from the floor.


    Note the "I.E.E." reference. 


    Andy. 110.1.3


    Z.


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