Dear all, I soon intend to install a 9.5kW electric shower to the home of a close friend whose bathroom I will be renovating. I have had previous experience with home electrics and have also worked with a qualified electrician rewiring a house once before, so I am not completely new to the subject. I have read the IEE installation method described on some DIY web sites and understand fairly well the proceedure for making such an installation. However, I am confused over one particular point of the installation. Whilst I understand the need for the use of an RCD unit in the connection of this device to the mains, I am not quite certain on how to use the unit. My friends CU is a fairly modern Wylex unit. It has a maximum rating of 100A on the main switch and is split into 2 sections, 1 with the mains ring and immersion heater on an RCD and the other with the remaining circuits such as the lights, cooker, etc. There are 3 empty fuse blocks (spares) on the side of the RCD. Whilst I understand that the shower unit must have its own 45A RCD, I am not sure whether to fit this on 2 of the 3 spare slots (shifting lower ampages across accordingly), or wether I should upgrade the existing RCD on the CU and add the shower to this through a 45A MCB or whether I should install a RCD unit seperate to the CU and have the electricity company link it to the meter. The other thing on my mind is that I will be installing a bath with a spa system and am not sure if this too will require a separate RCD or if it can be placed on the rail of the existing RCD in the CU. Please help if you have the answer. Thank You. P.S. I intend to get the final installation checked by a certified electrician before turning on the power, but I still want to get it done right so as to avoid timewasting.