Shower Tripping RCD on opposite bank

[bobbert]

Hey Guys

Having a problem with a shower tripping out the RCD feeding the opposite bank of MCBs.
The installation is TT with dual RCD board feeding 2 banks of MCBs.
When the shower is switched on, the RCD on the opposite bank of MCBs trips.
Having looked into the problem a little, it seems that the shower is somehow affecting the Ring Main upstairs (shower is downstairs) ... If I switch off the upstairs Ring breaker shower does not trip RCD.
Have ramp tested both RCDs and they seem fine so not a faulty RCD.
Have tested ring upstairs and this all seems ok too.
Any thoughts???

 

[topquark]

Checkout which neutral connections you have in which terminal block. All of the neutrals from RCD1 must be separate from RCD2.

 

[RWJ]

^^^^^^ Same as topquark check the neutrals

 

[Hawk81]

I will 3rd that. Sounds like shower neutral is in the wrong neutral bar.

 

[bobbert]

Thanks for the input guys.
Neutrals was one of the first things I looked at.
It's all sorted now ... Turns out the customer had a water heater hidden away at the property which they have never used or even knew about!!!
LOTS or pulling out of hair and a thorough search of the house led to this discovery.
Element (connected to ring cct) has developed a fault which was causing the problem. Disconected the heater as never used by customer and problem gone away!
I guess it was coincidence that this was not causing a problem before but I'm just glad it's fixed now