Floor Box sockets

dimspark · Jul 29, 2011

Hi all, tried to ask this in a bit more of a convaluted way so will keep this one simple. Customer has 150 flor boxes pluging into various busbar tracks via unfuse tap off leads. A few of the floor boxes only have 1 twin socket and we have been asked o upgrade these to have 2 twin sockets in. The busbar tracks ae supplied via 63amp mcd's. Will I be ok under current regs to simply wire up the new sockets or will I have to change all protective devices to RCBO's? Just concerend they will have constant nuisance ripping if I have o go down this route..

Any advice would be really helpful as Im struggling to come to terms with the regs on this one!!

dimspark · Jul 29, 2011

Orry for he terrible spelling, keyboard is rybbsh!!

Adam W · Jul 29, 2011

I'm going to stick my neck out and presume that this isn't in someone's house? Depending on the use an rcd isn't necessarily required - skilled and instructed persons, cabling in trunking etc.
Keep an eye on the cable sizes and how the sockets are wired as well - you don't want to go running a 2.5mm spur off a spur now do you?

hasel5 · Jul 29, 2011

Read the thread Adam

mogga · Jul 29, 2011

number 1 its a 63A busbar so the Tapoffs will be fused so fitting 2 sockets per box should be fine so long as its not for heavy loads 1 box per tap off if its 3ph watch your positining (400v) and load distribution
Number 2 RCBOs shouldnt be required as it seems to be surface

last project i worked on had 63A busbars under the floor with tapoffs mounted floor sockets in the raised floor and 2 rings round the perimeter on RCBOs for cleaners ect

Engineer54 · Jul 29, 2011

Just this week, i've been looking over a proposed raised floor distribution system for the IT building on my project. Slightly different in that the bus bar track is rated 32A with 5 numbers of tap-off to floor boxes, each bus bar track protected via DP 32A RCBO's. Each bus-bar track supplies 5 covered floor boxes containing 2 twin s/outlets (total 10 twins per bus-bar track). The bus-bar track is wired with 6mm, and the tap-off plug-ins are wired with 4mm..

So, ...how many tap-offs are there on each of these 63A bus bar tracks, what size cable on the plug-in tap-offs, to the floor units. Is that 63A MCB, suitable protection for these multiple small loads and cables??.

Engineer54 · Jul 29, 2011

mogga said:
number 1 its a 63A busbar so the Tapoffs will be fused so fitting 2 sockets per box should be fine so long as its not for heavy loads 1 box per tap off if its 3ph watch your positining (400v) and load distribution
Number 2 RCBOs shouldnt be required as it seems to be surface

last project i worked on had 63A busbars under the floor with tapoffs mounted floor sockets in the raised floor and 2 rings round the perimeter on RCBOs for cleaners ect

The OP said that these tap off plug-ins are ''Unfused''

[QUOTE:] Customer has 150 flor boxes pluging into various busbar tracks via unfuse tap off leads. [/QUOTE]

dimspark · Aug 3, 2011

Cheers guys as engineer 54 says, the 32 amp tap offs are unfused fed in 6mm. My thinking is downgrade the mob from a 63 amp to a 32 amp and split the floor boxes equally amongst the busbars. Downgrading to a 32amp hopefully means I can increase the tap off length from 3m as they all are to 5m in some cases which will allow me to split equally? Make sense and sound ok.. Fingers crossed....

malcolmsanford · Aug 3, 2011

Yes on the Ackermann system we use out here you can only use 3m+ tap offs on a track that is protected by a 32 amp protection device.

What we do here a lot is supply RCD sockets BS 7288 throughout the installation in various positions and normal BS 1363 sockets in other areas, it just means that we can use an MCB and not worry about nuisance tripping or high protective conductor currents.