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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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    as much as it would amuse me, having more unusual size MCBs fitted, nothing beats the 7.5a Dorman Smith breakers we have.


    I think the tendency to use 16a circuits for a dedicated fused spur is because we have a propensity to use a fused spur when really its not needed. If the circuit went from the MCB to the fixed alarm power supply with a 1a MCB, then the spur wouldn't be needed, even though 1.0mm still couldn't be used. 



    it sort of comes on to larger supplies in the factory where we have massively oversized MCCBs for a machine, like 63a, massive cable, but install an expensive switch fuse at the end to fuse it down to 16 or 20 amps, when it would be easier and cheaper to fit the correctly sized MCCB and a rotary isolator
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    as much as it would amuse me, having more unusual size MCBs fitted, nothing beats the 7.5a Dorman Smith breakers we have.


    I think the tendency to use 16a circuits for a dedicated fused spur is because we have a propensity to use a fused spur when really its not needed. If the circuit went from the MCB to the fixed alarm power supply with a 1a MCB, then the spur wouldn't be needed, even though 1.0mm still couldn't be used. 



    it sort of comes on to larger supplies in the factory where we have massively oversized MCCBs for a machine, like 63a, massive cable, but install an expensive switch fuse at the end to fuse it down to 16 or 20 amps, when it would be easier and cheaper to fit the correctly sized MCCB and a rotary isolator
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