RCD protection in an IT run office

I don't think that we were giving you a personal attack, it is a reflection on personal competence. You say you are fully qualified, perhaps you would like to list the qualifications, as I did above to be an Inspector working on EICRs. So I assume that you have the 18th exam, and your mark was 90% or more (very few achieve that) but inspectors should ideally get 100%. I assume you have a pass of 2391 before the last lot of changes with a pass rate of less than 30%, I have, first time and a prize. You say you have experience, then why the range of silly mistakes above which very few reading here even make in singles? Why do you not have a copy of BS7671 18th edition Amdt 1, or if you do why do you fail to understand the contents? There are a myriad of questions, particularly as you obviously don't know what an IT system is, when this is in section 710, and the section which mentions IT (ICT) is 331 and a few others. An inspector cannot work without a very thorough and accurate knowledge of the regulations, if not how can he inspect anything? It is simply not possible. If you have only an OSG, the job cannot be done at all, the OSG is a very simplified guide for the less experienced on how to do simple installations that are compliant, but not in any way optimum, just by following a few simple rules. The inspector must recognise all possible compliant installations and designs, and be able to check all the features even if they have never been seen by him before. A very difficult capability that requires a lot of knowledge and experience.


You should take this set of replies as something of a warning, not necessarily as a criticism. Inspection is probably harder than good design, particularly of larger installations. The risks of getting it wrong are much greater, everything from prosecution by the HSE under the EAWR, to claims of fraud or damages from clients, or loss of your Professional Indemnity Insurance which I presume you have. These may be rare but do happen, and getting PII after a significant claim may put you out of work for good. Please take notice, we are trying to help you. This is not the place to learn how to inspect but is the place where serious basic knowledge may be gained. If you work for a company that uses the QS system, you will be the first out of the door if your inspection has any mistakes contained in it, even if the QS signs. I have dealt with two cases of this, this week, both are untrue reflections of the installation, in order to gain reparation work and are basically fraudulent. I assure you that repercussions will follow for several people.


If you need help, JohnP is one of the most respected inspectors in the country. I would not advise you to be opposite him in court, but he often advises people here on some of the more difficult questions which are asked. Neither of us was trying to be rude in the usual forum sense, just honest.


Take care

David CEng Etc.

I would be interested in compliance with 543.7 for new and existing installations with many information technology computers.

https://professional-electrician.com/technical/high-protective-conductor-currents/


Z.

Joe


We are not being rude or insulting. It is clear you are not qualified or competent to carry out periodic inspections. What you are doing is putting the public at risk,and you are breaking the law. So please stop now!


If you want to work in the electrical industry start by signing up at your local college or training provider and do the 2 year course up to Level 3 in installation. At the same time gain experience with a competent electrical contractor working under supervision. Having got your Level 3 qualifications sign up on the Level 3 18th Edition course and gain the qualification. Then maybe AM2 NVQ3 and get your electrician JIB Gold card. Continue gaming experience workin as an electrician. Then study for and gain the 2391 inspect and test qualification. After 2 years you can get your JIB Approved Electrician Gold card. Work with an experienced electrical inspector gaining  experience of inspecting different types of installation. Work towards professional registration by applying for EngTech. with the IET. Throughout your career do CPD on a regular basis. This forum is a really good source of CPD as you can connect with a wide range of industry experts.

Going back to the original question - my thinking would be along these lines...


Current BS 7671 requirement is for sockets rated 32A or less to have 30mA additional protection - unless (for non-domestic premises) there's a documented risk assessment that concludes that additional protection is not necessary.


So first ask if there's a suitable RA. If so, all is fine.


If not, it's a non-conformity. How serious that is depends on the circumstances. I reckon an office environment is pretty similar (if not safer) than a domestic one in this kind of respect - so I'd probably code it in a similar way. Remember that the RCD is there to guard against high Zs after the socket (e.g. long outdoor extension leads) and accidental damage that exposes conductors (e.g. cutting through flexes with lawnmowers or plugging in seriously damaged equipment). Normally we'd code lack of 30mA additional protection for sockets as a C3 if the socket is only intended to serve interior areas, or C2 if serving outdoors (which might include an indoor socket if it looks like it might be used for feeding equipment outdoors). You might want to adjust that a bit for an office environment - e.g. if office policy is that people can't bring in their own appliances and there's little outdoors that would need a portable electricity supply (landscape maintenance contactors tend to use 2-stroke tools rather than electric and extension leads), they you could possibly afford to be a little more relaxed.


   - Andy.

Well Zoom, we have discussed this many times before. As Andy summarises the regs now are fairly clear (18th Amd 1) but in reality, it is not very dangerous unless one gets very unusual faults on the "Fixed wiring" to the sockets. Most of these installations should get a C3 and note that changing this to BS7671 compliance now, would be somewhat expensive because many more final circuits would be required, or the installation changed around to have an RCD local to a few sockets so that the leakage from the lot summed is less than about 10mA. At the same time, one might add high integrity Earthing to the circuits back to the board the installation is then completely compliant. It is a problem for offices with much IT equipment, as summed leakage can become quite high if there are perhaps 20 computers taking less than 3kW together but together having a leakage of 100mA. There is another point, which is the spectrum of the leakage current, and whether this will trip a typical RCD. Some is 50Hz so will, but the rest is entirely unknown and may be harmonics of 50Hz and switching frequencies and all kinds of frequencies to which the RCD may not be sensitive. The easiest way (which I have not seen anywhere!) would be to have a garage size CU by every desk with an RCD/MCB/RCBO feeding a number of local sockets. The feed to all these could be a high current ring, providing the high integrity Earth and power of whatever is needed. Fairly easy to install, even for island desks with a floor trap, and very fault resistant on any plugged-in equipment. I wonder if anyone else has seen this or any other ideas?

Inspection and testing requires very considerable experience, arguably more so than new installation work.

I agree and the standard BS7671 states this in a roundabout way. But the market will not give you that. The perception by those that have to pay for this service, is that Periodic Inspection is low level, low expectation and low price. It is viewed as an obstacle to be avoided or to magic away by paying the least amount possible, as most of  the time the requirement is forced.  Conversely, Installation work is far more profitable.


There has been a large amount of EICR P*RN posted here lately. As installation work is far more profitable it is not so much of a surprise if a firm manipulates this market to strike the balance. Sauce for the Goose and all that. At the other end, I know of firms that use Periodic Inspection jobs to keep busy  the low level operatives who are not capable of producing profitable installation work. One thing they are good at is filling in all those boxes on a tablet on site very quickly.   That they then routinely condemn everything is then seen as a win bonus situation by the employer. A particular cheeky one is the certificate software that "calculates" R1+R2 after they have measured Zs with their multifunction, low current/ no trip test, then magically "fails" the circuit on "higher than expected R1+R2 reading" and a Brucy Bonus of further investigation remedial work.. Why someone is "claiming" they have measured R1+R2 during periodic inspection when they have measured a healthy Zs, is beyond me, but is perhaps an indicator that they should not be doing this type of work in the first place.

Why would you measure R1 + R2 on a periodic inspection? What does this test prove? 


Clue to to the answers IET GN3!

For big offices the best way is to have floor track under a raised floor with purpose made leads from the floor track. The ends of the leads brought up to banks of desks with a strip of 13A sockets on the end of the cable. Each strip of sockets has  built in BS EN 61008 RCD protecting the sockets. Real plug and play installations.

If computer operation is important, and RCD/RCBO trips have serious consequences, than as a minimum, one RCD per workstation should be fitted.


In extreme cases were ANY trip would be unacceptable, consider either a reduced low voltage supply, or ELV supply, or high specification laptops with internal batteries.