Commercial premesis, computers, RCD or not to RCD?

[NellyManjaro]

As the title suggests I am doing an EICR for a commercial premises this morning.

I haven't looked at the job yet, it was a kind of "just come do what you need to do" job. It is an accountants which obviously means quite a few computers and I do believe they have a 3 phase supply but only uses 2 because the shop next door has the other (from what the client understands)

Now my question is because he has told me both CU's are 3036's... do I need to have the circuits RCD protected? I know he's happy to upgrade both units, I already suggested RCBO's and got the thumbs up but computers.... RCD's..... dont mix well as I'm aware?

I do believe that the computers are plugged into socket outlets and some of the cables are sunk into the wall so only trunking in certain places. But the office is fairly old

C2 on domestic for bathroom circuits and downstairs sockets but commercial downstairs sockets? Much more unlikely but potentially I suppose. Client is happy for RCBO's but can I fit them with computers say 8 computers per floor and 3 floors

Thanks for any assistance with this

 

[newfutile]

you will need to do risk assessments (written) if you omit rcd ,just find out the earth leakage per pc and multiply by number of pcs ,the regs state 9 ma maximum to prevent tripping though i would hope its much less than this !

 

[telectrix]

8 computers per RCBO, you might get away with it, butr what about printers and other IT witchcraft?

 

[littlespark]

So you do the EICR first and code accordingly. Your report can highlight the pros and cons of RCD protection on the notes page.
Then customer has an educated choice of whether to upgrade the boards. (But you should encourage him to do so)

The trouble is, when you start on the EICR, you’ll come across problems that may need sorted before a simple CU change.... Spurs off spurs for example.
Depending on how many computers are on each rcd may be a problem for cumulative earth leakage, but I think the wiring method would demand additional protection. (Less than 50mm buried?)

 

[NellyManjaro]

He happy to have done whatever is required... I was hoping that server room I can avoid RCD which I am hoping is in trunking etc but it's the earth leakage on the computers... is there a calculation to work this out? Something I've not had to worry about before

 

[Mike Johnson]

Two rings per floor, one for the computers and another for printers with a priority selector etc, only a thought.

 

[westward10]

The application of additional rcd protection for socket outlets and cables concealed in walls is no different to domestic so there is no comparison. Do you believe you have the necessary knowledge to be carrying out a commercial EICR.

 

[NellyManjaro]

The application of additional rcd protection for socket outlets and cables concealed in walls is no different to domestic so there is no comparison. Do you believe you have the necessary knowledge to be carrying out a commercial EICR.

Yes of course... as you said no different to domestic to which I have done 185 over the last 12 months alone. It was more a question of earth leakage on computers and rcd protection. In a perfect world all would be rcd protected. But things like the server room don't want it so assuming I can run a supply to server room in trunking with supplementary bonding and not require rcd protection same for computers but not always ideal or practical so was a question of is there a rule of thumb for how many computers per rcd

 

[Lister1987]

Selectable time delay RCD not a possibility no? I believe they can't be used in domestic but I think they ought to be allowed in commercial (what is the 7909 events industry if not commercial).

 

[pc1966]

The server room is fairly easy in the sense that it is normally controlled access and rack-mounted equipment can have supplementary bonding to the racks so you have very reliable ADS by that means. So it is easy to justify no RCD protection for them.

However, you really should have a "utility" socket or two in the server room for any cleaners use, test equipment, etc, so no one plugs in a faulty device and either shock themselves or trip the supply to all of the racks, etc. That should be RCD protected, of course.

General office outlets are more of a problem in that you can't be so sure of the usage. Some companies have a strict no-PAT/no-usage policy on anything brought it, others not. For desk sockets for office PCs in that case the risk is very low. But often offices will have sink/kettle/etc around so at the very least that sort of outlet should be RCD protected.

 

[stevethesparks]

However, you really should have a "utility" socket or two in the server room for any cleaners use, test equipment, etc, so no one plugs in a faulty device and either shock themselves or trip the supply to all of the racks, etc. That should be RCD protected, of course.

General office outlets are more of a problem in that you can't be so sure of the usage. Some companies have a strict no-PAT/no-usage policy on anything brought it, others not. For desk sockets for office PCs in that case the risk is very low. But often offices will have sink/kettle/etc around so at the very least that sort of outlet should be RCD protected.

Non -Standard MK sockets would sort that bit but would still have no RCD protection for buried cables less than 50mm

 

[westward10]

Non standard sockets would also require additional protection their configuration is not relevant. The risk assessment to omit additional rcd protection should be carried out by the client.

 

[pc1966]

Non -Standard MK sockets would sort that bit but would still have no RCD protection for buried cables less than 50mm

If the cables are < 50mm from walls then you do have that issue. If it is being rewired then that could be changed, either trunking or using Flexishield.

Non-standard sockets are an absolute pain as you can't use the supplied leads that come with kit, not can you take a chunk of stuff elsewhere to test it!

 

[Lister1987]

The server room is fairly easy in the sense that it is normally controlled access and rack-mounted equipment can have supplementary bonding to the racks so you have very reliable ADS by that means. So it is easy to justify no RCD protection for them.

However, you really should have a "utility" socket or two in the server room for any cleaners use, test equipment, etc, so no one plugs in a faulty device and either shock themselves or trip the supply to all of the racks, etc. That should be RCD protected, of course.

General office outlets are more of a problem in that you can't be so sure of the usage. Some companies have a strict no-PAT/no-usage policy on anything brought it, others not. For desk sockets for office PCs in that case the risk is very low. But often offices will have sink/kettle/etc around so at the very least that sort of outlet should be RCD protected.

Could find non standard T sockets (landlord sockets I think they often get called) for either Thier kit or tht cleaner, whichever is more likely to plug in non approved kit

 

[westward10]

Could find non standard T sockets (landlord sockets I think they often get called) for either Thier kit or tht cleaner, whichever is more likely to plug in non approved kit

What difference will using a non standard socket make the Regulations do not make allowances for this, it is a socket outlet.

 

[timhoward]

But things like the server room don't want it

You will likely find UPS units in the server room, powering racks, providing isolation in any case.

 

[Lister1987]

What difference will using a non standard socket make the Regulations do not make allowances for this, it is a socket outlet.

Oeam from a control POV, reducing the chances of something external being plugged in. Regs probably don't account for it as a control measure bit it's plausible

 

[catdog1121]

If its a genuine server room you might find that there are racks and each rack has two power distribution units, fed from two different circuits connected via commando sockets (so your not talking normal sockets) , as an ex IT engineer if you want redundancy then all but the really low end servers have the option for two or more PSU's, some of the blade systems we used a lot had 6 power supplies and you could lose upto 4 of them depending on the number of servers...

Power supplies in servers because of the heat etc commonly caused tripping, just ask a big bank when I started as an IT engineer, there was a faulty PSU, to test the psu was faulty not the cable or PDU etc I connected a spare power cable from the other PDU and plugged it into the faulty PSU to confirm that the PSU was actually bad before ordering a new one.... Well you see what I had not seen was that the faulty PSU had shorted taking out the circuit breaker rendering one of the two PDU's with no power, not a problem the servers carried on with the other PDU, that was until I connected that to the bad PSU, a big flash and bang later I tripped the other circuit breaker to the other PDU and took down all the servers in the rack, they controlled hundreds of ATM machines which all temporarily went down... I learnt a lesson that day that I never forgot and thankfully after a quick reset of the breaker everything came back up..

Anyway my point is until you get there you wont know what you are dealing with..