Shower Tripping Out help

[Ash4eva12]

Hi, I have a recently installed a 9.5kw shower on a 50a mcb wired in 10mm twin and earth...cable run is 2metres to a 45a switch then from that ...2metres to a dual rcd fuseboard 100a main switch with 63amp rcd x 2 ... The shower works ok on low settings but as soon as you turn it up to Eco or high it trips both the RCD's. However if you turn just one RCD on ...it will run fine on any setting low Eco or high and won't trip. As soon as you put both RCDs on and it's on Eco or high setting it trips both out. It doesn't matter wether it's on hot or cold setting either still get the same outcome as above. It's a brand new shower also. I have checked for cable damage all cables seem fine and also checked there are no crossed cables or that the neutrals are crossed on the board and are under the correct RCD bar. I'm baffled now as to why? Any help much appreciated. Thank you.

 

[Ash4eva12]

Sound a slight idiot saying it but 2nd time round looking at it...it took me all of 5 minutes to find. Whoever replaced the fuseboard had left the buzz rail uncut so both RCDs were connected together via the buzz bar. Schoolboy error and I can't believe I didn't spot it in the first place! Thanks all for help and advice anyway

 

[DPG]

Thanks for letting us know. We normally never find out! Daz