Truma hws keeps tripping circuit breaker

No. 3
That happens on many heater elements and the leak to earth does the CBD, spa heaters the same and house units too.

Seems many elements aren't super quality and have a relatively short life in that regard. The heater still works but it can't because of the inbuilt safety system.
That might be why some call them "Trauma".

Oh come on guys. You will start up another "Pedantic" argument by using the term "CBD".
Everyone knows it as an "RCD" or Safety Switch.
And please don't start lecturing me on the construction or history of the device...... I already know.

Allan,
they leak more int the CBD (central business district) than they do in an RCD ( regional business district)

Now is an earth leakage trip or a active neutral fault. Ha. Ha.

Ah well, it's not often that I try to crack a joke!

I'm not trying to light -gas - simply flicking the switch and it trips the circuit braker

HI
If it is tripping the 240V circuit overload breaker OR the RCD ,It realy is a job for an electrician !!!
Which ever it is you have a 240V fault .


PeterQ

Thanks everyone for your advice. Electrician coming up.