Shower circuit design.

I went to edit a spelling mistake and a post disappeared  altogether, the gist of it was that an E7 storage heater could have over 21 kW hours or more run through it in a heating period, so say you have three heaters plus an immersion in a big tank you are now heading up towards over 80 kW hours being distributed through circuits that could be protected by B16 MCBs and have 1.5 mm twin and earth running up insulated 4” stud walls and under 4” of loft insulation.

The MCBs and cables have to warm up, you cannot assume that appliance will only run for a short period like an electric shower generally will, running maybe around 2 kW hours through a much larger cable.

Which is why EV granny leads restrict charging to less than the 13 amp socket capacity as they may run over 30 kW hours through the socket and the circuit, which may be of unknown providence with an unknown design.

I went to edit a spelling mistake and a post disappeared  altogether, the gist of it was that an E7 storage heater could have over 21 kW hours or more run through it in a heating period, so say you have three heaters plus an immersion in a big tank you are now heading up towards over 80 kW hours being distributed through circuits that could be protected by B16 MCBs and have 1.5 mm twin and earth running up insulated 4” stud walls and under 4” of loft insulation.

The MCBs and cables have to warm up, you cannot assume that appliance will only run for a short period like an electric shower generally will, running maybe around 2 kW hours through a much larger cable.

Which is why EV granny leads restrict charging to less than the 13 amp socket capacity as they may run over 30 kW hours through the socket and the circuit, which may be of unknown providence with an unknown design.