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

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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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  • 0
    AJJewsbury:
    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.

    BS 7671 definition of a circuit means that any overcurrent protective device starts a new circuit (see part 2) - in this case the L and SL are by definition different circuits as the are protected by different fuses. As they both directly connect to current using equipment they'd be classed as final circuits.


    Oddly enough there's nothing in the definitions that means that one final circuit can't supply another final circuit (despite the name).


       - Andy.


    Circuit definition. "An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s)." Notice the plural used here DEVICES.


    "Same origin." Yes the lighting circuit M.C.B., say a B6 or B10.


    "An assembly of electrical equipment."  Yes, Lights, shaver outlet and fan.


    We could argue about the fuses used to protect the fan are just there for fault protection and not overcurrent protection as the fixed fan load can not overload the supply cables in normal use.


    "Protective device(s)" can be included in one final circuit. So we can have more than one protective device in a final circuit.


    Z.


     


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  • 0
    AJJewsbury:
    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.

    BS 7671 definition of a circuit means that any overcurrent protective device starts a new circuit (see part 2) - in this case the L and SL are by definition different circuits as the are protected by different fuses. As they both directly connect to current using equipment they'd be classed as final circuits.


    Oddly enough there's nothing in the definitions that means that one final circuit can't supply another final circuit (despite the name).


       - Andy.


    Circuit definition. "An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s)." Notice the plural used here DEVICES.


    "Same origin." Yes the lighting circuit M.C.B., say a B6 or B10.


    "An assembly of electrical equipment."  Yes, Lights, shaver outlet and fan.


    We could argue about the fuses used to protect the fan are just there for fault protection and not overcurrent protection as the fixed fan load can not overload the supply cables in normal use.


    "Protective device(s)" can be included in one final circuit. So we can have more than one protective device in a final circuit.


    Z.


     


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