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Fuses for showers.

Sparkingchip
From a electric shower installation manual:


Circuit Protection Table

Circuit Protection Device


Unit Rating (@ 240V)

8.5kW

MCB 40A

Cartridge Fuse 45A


9.5kW

MCB 40/45A

Cartridge Fuse 45A


Why a 45 amp cartridge fuse for a 8.5kW shower or for that matter even the 9.5 kW shower?


I presume it must be time related as the 8.5 kW shower will only load a 40 amp fuse to around 90% of its capacity.


How long can cartridge fuses be run at 90% capacity for?


 Andy B.
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    geoffsd:

    Manufacturer's instructions are frequently wrong or unnecessary.




    Given that if an existing fuse holder will take a choice of three available fuses, the 40-amp cartridge fuse seems the appropriate choice for a 35.5-amp 8.5 kW shower rather than either the 35 or 45-amp fuses as it will probably run around 36 to 37-amps.


     Andy B.

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  • 0

    geoffsd:

    Manufacturer's instructions are frequently wrong or unnecessary.




    Given that if an existing fuse holder will take a choice of three available fuses, the 40-amp cartridge fuse seems the appropriate choice for a 35.5-amp 8.5 kW shower rather than either the 35 or 45-amp fuses as it will probably run around 36 to 37-amps.


     Andy B.

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