RCBO's on under floor bus bars

[dimspark]

I've been asked to spec up a job at a newish office block. Raised flooring has been installed with bus bars and tap off leads. Bus bars have been installed using 10mm swa with 63amp MCB, tap off leads have 32 amp unfused plugs on them.. There are about 12 floor boxes per bus bar and 4 bus bars in total. There could easily be about 24 workststions eventually fed off 1 bus bar which doesnt concern me load wise but an RCBO wont enjoy the earth leakage off the computers. Anyone suggest a work around or is it a rewire job?
Also, am I missing something but how/why are the plugs unfused?

Any help much appreciated

 

[Gilez]

The plug-in tap-offs dont need to be fused if they are under 5m in length if from a 63A busbar (they typically come in 3 or 5m lengths, so guess you have 3m ones). 5m tap-offs can be unfused too if the busbar is rated no higher than 32A.

You should check the earthing arrangement to the busbar for high earth leakage currents as a start. With regard to RCBO's it will depend on the spec you are working to. It could be assumed that the building, as a commercial building, is under the supervision of a skilled or instructed person as required by the Electric at Work Regs and, as such, the RCBO's could be swapped to circuit breakers. The other way is to reduce the lengths of busbar down (you dont say the length) and provide additional circuits and end feed units, but this will obvioulsy attract more cost.

 

[johnboy6083]

the reason that the plugs dont have to be fused if 3m , si that the fuse on the circuit it supplies, will protect the cabl;e from overload. a short circuit will take out the main fuse protecting the busbar. this is exactly the same as all distribution panels, and control panels. the one i was working on today, the busbar is rated at over 1Ka. my tap off was wired in 240mm2 double insulated tails, to a switchfuse, rated at 400A. from there it supplies another panel. the $00A switchfuse protects the 240mm tails, as any current drawn has to go through the switchfuse. in the unlikely event of a short circuit in the tails, ity will take out the main ACB of the panel, that supplies the busbar.