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60A main Fuse, should I upgrade?

Former Community Member
Former Community Member

Supplier main Fuse is 60A and current consumer unit has 80A RCD (61008) as isolator with a notice saying 'Max load not to exceed 80A". Property is one storey with 5 rooms. Currently have 8 circuits, 2 lights with B10s, 2 ring finals with B32s, Cooker with B40, Shower with B40, Water Heater with B16 & Garage feed to a sub board with C40. Want to add a new 10.5kw shower so will need 50A protective device but not sure if should be approaching the DNO for an upgrade of the main fuse as running both showers together alone will draw a decent load

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    Thanks Andy. Referring back to table 3A3(b) though isn't the data essentially saying that a 63A fuse will require roughly 100A of load for an hour before it begins to operate or am I misunderstanding the chart?

    It's more saying that the fuse is guaranteed to open in that time for that current (the sort of reassurance you need for protecting conductors from thermal damage, or (for higher currents/shorter durations) that disconnection will be fast enough for ADS). Any given individual fuse is free to open quicker than that though - and the vast majority will be quicker to some extent (just due to manufacturing tolerances and need to stay below prescribed upper limits).  If the 1.25x non-fusing factor is correct, then all we can really say is that a 60A fuse will open in an hour at something between 75A and 100A. Lower currents (but above) 60A will take longer (perhaps infinitely long), higher currents will be quicker.

       - Andy.

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  • 0

    Thanks Andy. Referring back to table 3A3(b) though isn't the data essentially saying that a 63A fuse will require roughly 100A of load for an hour before it begins to operate or am I misunderstanding the chart?

    It's more saying that the fuse is guaranteed to open in that time for that current (the sort of reassurance you need for protecting conductors from thermal damage, or (for higher currents/shorter durations) that disconnection will be fast enough for ADS). Any given individual fuse is free to open quicker than that though - and the vast majority will be quicker to some extent (just due to manufacturing tolerances and need to stay below prescribed upper limits).  If the 1.25x non-fusing factor is correct, then all we can really say is that a 60A fuse will open in an hour at something between 75A and 100A. Lower currents (but above) 60A will take longer (perhaps infinitely long), higher currents will be quicker.

       - Andy.

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