A client of mine (IT company in which most users have one laptop and either one or two monitor power supplies on their desk - a few with more) is having a distribution board change as part of an office refurb. The existing final rings are not RCD protected (last significant works were done about 10 years ago).
The installer is proposing to feed the rings from RCBOs.
The laptops (those which have class 1 supplies, which are the majority) are presumably permitted up to 0.75 mA earth leakage each. I presume the monitors are also classed as "portable equipment" and so are also permitted 0.75 mA each (if not they're permitted 3.5 mA each I think).
Does anyone have any recently measured figures on average per-desk leakage? Do they tend to stick reasonably close to this 0.75 mA, or in practice are most considerably under?
I'm assuming they should try and keep below around 10 mA on each 30 mA RCD/RCBO to have a comfortable margin for nuisance tripping?
I also presume the final rings are likely to be pretty lightly loaded, so splitting them to radials might be another option, effectively halving the leakage each RCBO will see?
Cheers,
Tim.
