Use of RCD protection in industrial and commercial installations

Hello Andy,

Where circuits are protected by RCD (the residual current device) we must perform a test to ensure that the device operates very quickly under fault conditions and within the time limits set by the IEE regulations. The device must, therefore, simulate a fault and measure how long the RCD will operate. The device is, therefore, calibrated to give a measured reading in milliseconds a 10% accuracy of service.

Hello Davodian,

                         Thank you very much for your reply. I understand the testing rational behind RCDs and the safety benefits they afford, The issue I have is the use of RCDs in a high volume production environment, switching of this equipment for testing is problematic not just in down time but re calibration of equipment and that's not to mention nuisance tripping. I was just wondering if RCDs really need to be used clean dry areas especially when the production operatives all ware compulsory PPE.


Thanks again


Andy

you may get more answers re-posting this in the wiring /regs forum, as far more people visit it, importantly more of  those actually working 'in the field' as it were.

or ask Lisa Miles‍ if it can be moved.

From my personal side, it very much depends what is being plugged in - if 'ordinary folk' are plugging in the phone charger they brought in from home, or some appliance of unknown vintage with a frayed flex, it  is a far less controlled case than a  socket in a controlled access building that supplies a specific piece of fixed apparatus, or is only used by trained personnel.

In many ways the regs do not acknowledge this.

One might like the RCD sockets to be more common, and the wiring to be MCB only and in metal trunk, but it is a bit tricky due to a coverage gap between the standards committee that do the RCD sockets and spurs, and the one that does the wiring regs, at the moment you can read the regs as saying they cannot be used, as they are not called up in a list of approved standards.

being asked if RCDs are required for normal switched socket circuits in industrial installations

The default answer is yes, unless there is a documented risk assessment stating no such protection is necessary. The Duty Holder for the Installation should be making this decision, not the electrician being asked to install sockets or the Inspector assessing the Installation.

The issue I have is the use of RCDs in a high volume production environment, switching of this equipment for testing is problematic not just in down time but re calibration of equipment and that's not to mention nuisance tripping.


One assumes you have full a UPS system in place?


Regards


BOD

IMHO, RCD protection IS required for socket outlets under all commonplace circumstances in workplaces.

It would in my view be reasonable to use RCD socket outlets in many cases so as to limit the consequences of earth leakage to a single item of equipment. And whilst it can be argued that RCD socket outlets are not "approved" by the wiring regs, it would in my view be reasonable to list this as a departure from the regs, but one that provides an equivalent degree of safety.

Much better in effect to say "we have provided equivalent safety measures by use of RCD socket outlets" than to say "we omitted RCD protection because it would risk downtime"

The wiring system must of course be a type that does not need RCD protection.


If the conditions are indeed clean, dry, and well maintained, then RCD trips should be exceedingly rare events.


If even very rare RCD trips are intolerable, then it might be worth considering alternatives to mains voltage as a source of energy. Alternatives might include SELV, pneumatic power, hydraulic power, small dry cells, or other alternatives that carry no risk of dangerous electric shock.


As regards process shutdowns for RCD testing, it MIGHT be possible to argue that intervals between such tests could be extended in low risk situations, provided that the RCDs ARE tested whenever possible such as when a plant stoppage occurs for some other reasons. Better an RCD tested less frequently, than no RCD !.


One installation in which I was involved was a continual production process, any stoppage of which would be costly. Numerous sensors and instruments for measuring temperature, pressure, weight, or humidity were involved. These all used ELV derived from small plug top PSUs, all were plugged into RCD sockets, not one of which has ever tripped.

I do not understand the question. 

I want to help. 

Is it possible to be a clear brand ?

Rack mounted computer equipment doesn't have to connect via a 'socket-outlet'; cable couplers and appliance outlets could be used instead, and in this case:

(a) BS 7671 does NOT require RCD protection, as Regulation 411.3.3 only requires RCD protection for socket-outlets, NOT cable couplers and appliance connectors.

(b) Additional protection should be in place by providing supplementary local equipotential bonding, which is required by BS EN 50310 (and this is referenced from BS 7671 for such installations in Section 444).

(c) Such equipment is usually housed in locked enclosures to prevent tampering in any case.


If a particular circuit is critical for safety services or business functions, surely socket-outlets would not be the preferred option, to prevent accidental "unplugging".


In industrial applications, there are a number of other functional and safety considerations, and again connection via plug and socket-outlet is not necessary.

If a particular circuit is critical for safety services or business functions, surely socket-outlets would not be the preferred option, to prevent accidental "unplugging".

But on the the other hand BS 1363 &  BS EN 60309 sockets are often preferred for more mundane practical reasons - as it allows authorized (but not electrically skilled) personel to move things about when required (especially in (business) "emergency" situations), and indeed allows such personal to install new equipment that'll usually come with a conventional plug pre-fitted - especially at lot of the smller kit that needs a 'wall wart' supply that can only (practically) be plugged into a 13A socket. I've worked in many a small office "machine room" and 13A sockets are certainly the norm. Big data centres where everything is racked might be a different kettle of fish (but even then it's not unusual for a rack to be supplied via BS EN 60309 devices.


For a small office machine room kind of situation where access is limited, I would have thought that it should be reasonably straight forward to come up with a risk assessment that, along with a few basic precautions written into the site rules, that 30mA RCD don't provide a significant safety benefit and so may safely be omitted.


   - Andy.