Sauna outside

you can get both 3 phase, and 3 phase with neutral, but not cheap, and you may be cheaper and same effect, to have separates, and then if running in armoured cable there is also an option to put the MCB indoors and the RCD part outdoors, especially if the MCB is in some sort of locked plant room. 

Is there a need for the neutral ? (for example would be if 230V pump perhaps and 3 230V heaters  but not if all loads were phase -phase 400V or perfect balance ?)

Be careful - there are some makes with designs intended for 3p bus bars with neutral fly wires..
example  note 4 screws on top and 3 below ;-)  

others are more conventional  4 in 4 out
Of course sods law says that the ones that fit the box you have are not available in the right style.

Is the house earth PME ? If so there may be merit in considering making the sauna a TT island, but maybe not, depending what else is nearby connected to the house earth that may be simultaneously accessible. 
you can always add a rod to an existing PME installation but it does not do a lot to hold the voltage down, as the rod resistance to earth is always much higher than the supply neutral impedance.

M

Apparently hager said i need a standard 3 phase mcb and then a rcd attachment to make it a rcbo effectively 

This sauna is 9kw so I think 3 x 3kw heating elements 

This sort of thing?

I am a wee bit confused. How can a sauna be outside?

Its a special stand alone unit all outside 

So, a shed?

Chris Pearson said:

So, a shed?

Or, a 'building' ?

Chris Pearson said:

So, a shed?

Or, a 'building' ?

I guess a shed of sorts, be a wooden outbuilding with a sauna room inside, a cold water outside shower outside I imagine