new shower-tripping rcd

[topbanana]

bit of a problem which i would be grateful if someone could give me some assistance.
bought a new mira sport 9.8 kw shower.
bought a new 50amp mcb for an existing contactum split load box and positioned on 80amp 30 ma rcd side.
switched on mcb all ok.
switched on 45amp cooker type switch outside bathroom- all ok with power light on at shower unit.
pushed the start button on the shower and the rcd trips.
could this be a problem with the shower? can i check this by connecting something else to the shower lead.
by the way all cabling 10mm.
i turned everything else off at circuit board just in case after first attempt, with the same result.

 

[Spark123]

Firstly, as this is split load have you connected to the correct neutral rail in the CU?

 

[Adam_151]

Check you have the neutral in the correct neutral bar

 

[andy]

might aswell say the same thing: neutral is connected to the wrong side.

 

[securespark]

And if all those tips fail to solve the problem, you might check whether the neutral conductor is residing in the correct busbar.

 

[topbanana]

spot on all.
neutral on wrong bar.
thanks very much

 

[ban-all-sheds]

I was going to suggest that.