Underfloor Bus Bar Systems

As someone has pointed out "what is the issue here". The issue in my case is not the tap-off's in use as they all will feed Floor boxes which have RCD Sockets, the issue is the spare ways on the Bus Bars. Clearly if the tap-offs are classed as sockets then they have to be RCD protected and this is not a practical solution at the tap-off locations given the quantity, therefore the only solution would be to protect the total Bus Bar at source. The Client does not want the inconvenience of a possible nuisance trip taking out a substantial amount of Desks and is also unwilling to produce a risk assessment to omit the RCD (for the spare tap-offs) which in my opinion would be an acceptable solution and would probably be accepted by the Designer. In the past some Bus Bar suppliers tap-offs were actually 13amp sockets but I am not sure if this is still the case. The obvious and best solution would be that Bus Bars tap-offs are not classed as Sockets to give the Designer some form of comfort. As a side issue PDU strips within Data Cabinets are a similar issue in terms of protection.

From a practical perspective, the thing about a socket outlet is that any unskilled person can plug in any old piece of junk (e.g. lawnmower with frayed flex), which the designer has no control over. So you want the socket RCD protected. For fixed equipment, the designer has more control: they get to choose what's wired into the FCU, and how well the flex is protected etc.


So, if cleaning staff are turning up and plugging random industrial-sized portable cleaning equipment into your bus bar, you might want RCD protection. On the other hand if only a small selection of skilled staff are authorised / have access to the bus bar, and they know when to include an RCD with the equipment, then the bus bar shouldn't need RCD protection.


Whether BS 7671 agrees with that is of course a separate matter.

BS7671 does handle this. you turn it into a risk assessment.  You say (to paraphrase slightly)


Risk assessment 001
Nature of risk

1) There is a potential risk from folk plugging random equipment into this bus bar, as there is  no RCD protection.

2) There is also a risk if the bus bar is damaged in a way that a live core is exposed .
if unmanaged the risk of injury is moderate.

Management of risk


To mitigate this risk,.

1) We will not allow random equipment to be connected to the non RCD bus bar, and

2) Those carrying out building works involving cutting or drilling near the bus bar shall check with  authorised persons before proceeding.

3) We shall put labels to that effect on any unused points of termination and places where the bus bar is easily accessible.

4) Only a small selection of skilled staff are authorized to have access to the bus bar, and they shall be qualified to decide when to include an RCD with the equipment.

I understand on the basis of the evidence presented to me that the residual risk after the

above mitigation measures have been put in place is negligable.


Insert near illegible signature of company director and / or company health and safety officer.