I don’t know all the details. Are you sure you’re literally not allowed to place anything before the RCD? Technically SPD then RCD makes the most sense to me, so it seems strange to me that it wouldn’t be allowed, but I couldn’t find any clear answer.
I have a suspicion that the kind of surge protector rating it’s reasonable to fit to the main electrical input for a building is unlikely to actually trigger on the small surges that the surge protector in a UPS will, and you will still get earth-leakage trips on the RCDs with UPSs downstream of them.
Having one radial (for the computer rack) NOT protected by an RCD seems like a cheaper and more reliable solution, but I confess it’s not bubbled to the top of my to-do list yet to get a sparky involved for advice.
I don’t know all the details. Are you sure you’re literally not allowed to place anything before the RCD? Technically SPD then RCD makes the most sense to me, so it seems strange to me that it wouldn’t be allowed, but I couldn’t find any clear answer.
I have a suspicion that the kind of surge protector rating it’s reasonable to fit to the main electrical input for a building is unlikely to actually trigger on the small surges that the surge protector in a UPS will, and you will still get earth-leakage trips on the RCDs with UPSs downstream of them.
Having one radial (for the computer rack) NOT protected by an RCD seems like a cheaper and more reliable solution, but I confess it’s not bubbled to the top of my to-do list yet to get a sparky involved for advice.