Isolation Transformer RCD advice

[el donkey]

I have picked up an older but quality isolation transformer. 3kva

240v to 240v uk spec.

It has a power flip switch plus an rcd module. That has a test button which is connected to L2. The case has an addition test button which is linking to L1

However pressing either fails to trip the power switch.

I assume the rcd unit is no longer working.

Anything I should be aware of when replacing.

I could remove the old switch gear, fit a domestic off switch to the incoming side and a spur type domestic rcd to the output but will that cover both L1 + L2 ?

The input has L N E

The output L1 L2 E CT

The input and output E are linked

Or I try and find an rcd that matches the original. I am assuming it was all wired correctly.

Thanks.

 

[el donkey]

Pics attached