UK RCDs Underrated?

[nexus32]

Hi. Could you please advise on whether 63A RCDs are acceptable when the service fuse is 80A? I have the following setup: 80A service fuse - 100A main switch - 63A RCD x2. Each RCD has three circuits. First RCD: Shower 40A + Sockets 32A + Lights 6A. Second RCD: Cooker 40A + Sockets 32A + Lights 6A. So potentially a maximum of 78A per RCD. Realistically it’s not going to get to 78A, but should one side go over 63A, won’t it burn out the RCD? If we were talking about a single 63A RCD on a 60A service fuse, then it wouldn’t be an issue as the fuse would blow before the RCD got overloaded, but in this case as the 80A fuse is upstream of the 63A RCD, even disregarding what circuits are involved, aren’t we talking about a potential for the RCDs burning out, and ideally they should be replaced with ones at 80A surely? Many thanks.

 

[Strima]

Unless you're growing something illegal in the loft your sockets will never draw 32 amps. Same for lighting. Once your oven gets to temperature it cycles through heating so will not draw much current, the only item that will is your shower whilst you use it.

The RCDs, although rated for 63 amps, will take more for short durations.

There's millions of homes in the UK with this set up and have no issues with failing RCDs.

However a recent change in the wiring regulations now requires us to install RCDs that are rated to that of the main fuse, but this does not have to be retrospectively applied and only applies to new installations.