Electric shower Tripping.

Hi there, Your 10.5kw electric shower should be pulling around 45 amps so for It to be tripping out a 50 amp breaker it sounds to me like there could be an issue with the load side of the main supply as you've already replaced the shower. Troubleshooting advice: 1) if you can you turn the shower breaker on with the shower isolator In the off position and the shower not turned on and it does not trip.... main electrical supply appears to be electrically sound. (if it trips the breaker in this situation the main electrical supply would need to be assessed) 2) if you can you turn the shower breaker on with the shower isolator In the on position and the shower not turned on and it does not trip.... electrical supply appears to be electrically sound. (if the breaker does trip in this situation the electrical wiring would need checking from the isolator to the shower) 3) if you can you turn the shower breaker on with the shower isolator In the on position and shower turned on and it does trip.... most likely a faulty shower or shower has been wired incorrectly. I hope this helps you to resolving your electrical issue.

Could be the insulation on the cable breaking down under load. Suggest you get an electrician out to give it an insulation test with the appropriate test equipment.

Sounds as if the cable is overheating this would case the MCB/RCBO to trip. It is possible that it runs through solid cement, wood or insulation. Or else could be a minor water leak that causes a short to trip the RCD.