shower faulty?

[maffa ent]

i went to a shower that was playing up, found and replaced internal heat damaged cable, tested all working ok, and left. advised of problems (9.5kw on 4mm, 32a mcb, badly done whole house refurb by developer in 2007, recommended eicr and remedial)

they called today to say mcb tripping over weekend. went back, and checked with ammeter, current being used - 39amps.

then shower started to draw only 31 amps, and i couldn't get it to draw 39 again for the life of me! water temp and current draw alter from low, half and full power settings, but no 39 amps??

any ideas please? weakened mcb? faulty shower?

 

[Sparky Ninja]

A 9.5kW shower will draw up to 41Amps.

The protective device is undersized, and the cable size should be assessed too.

The inability to get 39Amps again is either the way you didn't demand maximum temperature, or due to the cycling with the appliance itself.

Regardless.

Ib < In < Iz this coordination has not been achieved.