Advice on RCD Protection for commercial office sockets (earth leakage)

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New member
Jun 12, 2022
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Hi guys,

I've got a job where I'm installing dado trunking on the floor of an office for sockets and data. Some info on job - In total I will be installing 36 double sockets to supply 40 workstations. Majority of the workstations will be a laptop with dual monitors and phone setup. Some of the workstations will have desktop PCs or the smaller NUC style PCs. Some of the sockets allowed are to be installed between the desk locations due the customer wanting some redundancy and flexibility in moving desks. The rows of desks come out vertically from the wall the dado trunking will be located on and site plan to run extension leads from the sockets to supply all equipment. They've requested this as their current setup with floor boxes has caused them a lot of issues and they want flexibility to move the desks forwards/backwards with cable management installed on the back of desks.

Where I'm looking for advice is the best way to provide RCD protection to all of these sockets without having fault issues due to earth leakage.

I've seen varied information on how many PCs should be connected to one RCD circuit from 3-4 to 8 PCs per circuit. I plan to install a new board and run radials for the sockets however I'm not sure how many workstations I should be wiring for one circuit due to earth leakage and it seems like it could require a lot of circuits needed just to stop nuisance tripping.

Is there a better way to go about this or a standard for larger office installations like this ?

The other option I was considering is installing RCD sockets instead of RCBOs however I'm not sure if this is a common way of doing an installation like this with so many sockets or if it would be considered ‘rough’. Using RCD sockets would allow for two rings to be wired for the whole floor which offset the extra socket costs compared to running lots of radials and rcbos/bigger board. Also the added benefit of not tripping out the full circuit if a fault occurs, not as big of a deal as they mostly use laptops but still helpful. Would using RCD sockets like this be considered good practice?

I was also planning to install high integrity earthing by linking out the last socket of each radial in the dado with a 4mm CPC, from what I can tell this is the correct way of achieving it.

Any thoughts or advice would be much appreciated.


eco warrior......™
Supporting Member
May 7, 2008
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Sunny Plymouth
I've seen large office spaces with 100mA RCDs, but that was prior to recent regs changes.

I'm a little surprised by extension leads, most places are trying to eliminate those.