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MCB size for dedicated fused spurs

Johno12345
A little thought, when installing a new circuit for a fused spur to supply an alarm or something similar, just about everyone uses a standard 2.5mm radial circuit, but the MCB size seems to vary from 16a down to 6. 


part of me (the larger part) thinks, just keep it standard 16a, and another part says to size the breaker to the load 


(I'm a specifier, not installer)
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    A supply to an alarm system or control system is definitely a power circuit. The function of the circuit is definitely not not "signalling and control".

    My original example was for a smoke alarm circuit (no separate FCU) - the argument being that the function of the entire circuit was to provide a danger warning (signal) to occupants. Any signalling or control circuit must draw some power in order to operate. I agree a supply to a FCU to something which in turn might supply a signaling circuit is less clear.


    On the other side of the coin, where would a power-over-ethernet (PoE) cable fit in this scheme? (especially one where only the power was used at the far end - say for a separate CCTV illuminator - so the data path was unused).


      - Andy.
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  • 0
    A supply to an alarm system or control system is definitely a power circuit. The function of the circuit is definitely not not "signalling and control".

    My original example was for a smoke alarm circuit (no separate FCU) - the argument being that the function of the entire circuit was to provide a danger warning (signal) to occupants. Any signalling or control circuit must draw some power in order to operate. I agree a supply to a FCU to something which in turn might supply a signaling circuit is less clear.


    On the other side of the coin, where would a power-over-ethernet (PoE) cable fit in this scheme? (especially one where only the power was used at the far end - say for a separate CCTV illuminator - so the data path was unused).


      - Andy.
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