Many computers in office. How many circuit breakers?

[ericmark]

Since 3.5 mA is the limit before special plugs and sockets need to be used "543.7.1.1" I would take that as maximum over that I would regard the item as faulty. At 1/2 rated value before any RCD should trip that means 4 sockets per RCD use X-Pole RCD's rated at 90% you can go up to 8 sockets.

Considering that all computers are unlikely to draw the maximum I would consider one should be able to double the number of sockets so putting 16 sockets per RCD would seem reasonable.

Since servers may require a more secure supply then 10 sockets to supply servers would also seem reasonable.

The advantage with X-Pole there is an indication when approaching the limit they don't just trip.

What I have discussed many times is who has access to reset a trip whatever type? If the distribution unit is locked then having a sub-unit where the RCD is accessible may be an option?

Of course RCD sockets are made and if really unsure one could use all RCD sockets although I have had issues with these. In theroy a 100 mA S type RCD in distribution unit should not trip before the 10 mA RCD sockets. But in practice pressing the test button on the 10 mA RCD sockets would also trip the 100 mA S type.

In industry the risk assessment and method statement is the norm and to me one needs to write out something which shows one has thought about the problems and has made a decision based on this.

The main idea is pass the buck. As long as one writes down what the problems are if the client accepts this then no problem for you. If however you fail to inform them then your clearly to some degree responsible for rectifying problems.

 

[dhutch]

Fit 3 x 32A, 30mA RCBOs and run [two 4mm] radials off each RCBO.

Each radial will feed 5 socket outlets - giving 30 outlets in total.

Im nto qualified to do the job, but that makes most sence to me, given the limitations, including reducing the effect a trip which would only take out 1/3 of the computers not all.

If there is a central server i would put that on a dedicated circuit.

Edited to make it more clear that I agree there is no point in running two radials of the one RCBO over an above running a single radial (or a ring, proximity of CU dependant).


Daniel

 

[JohnW2]

Fit 3 x 32A, 30mA RCBOs and run [two 4mm] radials off each RCBO.Each radial will feed 5 socket outlets - giving 30 outlets in total.

Im nto qualified to do the job, but that makes most sence to me, given the limitations, including reducing the effect a trip which would only take out 1/3 of the computers not all.

As Electrifying agreed last night when I pointed it out to him, there's really no advantage of having two 4mm² radials running from each 32A RCBO, unless that proves to be more efficient for cabling because of the locations of the sockets. Otherwise, you might just as well have one 4mm² radial circuit off each RCBO.

Kind Regards, John

 

[holmslaw]

..

 

[dhutch]

[quote="dhutch";p="2320727As Electrifying agreed last night when I pointed it out to him, there's really no advantage of having two 4mm² radials running from each 32A RCBO

Thats why i put the 'two radials' bit of the quoted texted in brackets, but prehaps that wasnt overly clear. Post edited.

Obviously it still leaves the debate of providing non-rcd protected outlets for PCs but thats between the contractor and the customer to a certain extent.


Daniel

 

[OwainDIYer]

sorry for all the questions - electrician is subcontracted and I have to communicate to him via contractor as he doesn't speak english

So how is he going to complete the certificates if he doesn't understand them?

 

[JohnW2]

Thats why i put the 'two radials' bit of the quoted texted in brackets, but prehaps that wasnt overly clear. Post edited.

Apologies - I didn't even notice (or, at least, 'take in') the brackets. We seem agreed, then.

Kind Regards, John.