Electric shower

[martinh89]

Hi guys it's been a while since I've been on here, but I got called to a job today for an electric shower tripping the mcb.
Upon investigation the shower is 9.8kw on a 32amp type b mcb. My first thought was it's being wrongly rated but I decided to carry on with a few checks. whilst on it heats up perfectly fine and stays on for around 5 minutes before tripping the mcb not the rcd. I checked all terminations for tightness, bypassed the neon in the dp pull switch and did an ir test, and it came back fine.
My question is with the shower being a purely resistive load could it take time for the shower to reach its operating current or would it be instantaneous? The consumer unit is Eaton, and they only do 40amp so I've ordered a 50amp type b for the shower circuit.

The cable route from what I've traced is around 17meters and it's clipped direct.
Thanks for any advice.

 

[martinh89]

Yes I did ask for your opinions good or bad I would like to hear them, it's only going to make me better at what I do, I would like to consider my self as an engineer yes, 4 year apprenticeship and 5 years as an electrician and hnc under my belt so I'd like to think so at least

 

[westward10]

Okay engineering judgement made. Me personally I would not be happy, would the cable overload, probably not, would conductors rise to a temperature which may effect the insulation, maybe. And it is the latter which would concern me because ratings of cables are judged on the conductor not rising to a temperature which could cause harmful effects to the insulation.