general advice reqd

[bobby101]

hi all going to be doing a small refurb on a small single unit, what i would like to is this know is the client is going to fitting in several pc points and server would it be good practice to fit a sub board for all the clean supplies with additional protection or will fitting a slit board be suffice also would like ask does fitting filter sockets or plugs cause nuinace tripping

 

[IQ Electrical]

hi all going to be doing a small refurb on a small single unit, what i would like to is this know is the client is going to fitting in several pc points and server would it be good practice to fit a sub board for all the clean supplies with additional protection or will fitting a slit board be suffice also would like ask does fitting filter sockets or plugs cause nuinace tripping

What are the other loads comprised of (welders, motors?) were clean supplies specified?

 

[bobby101]

the other loads are general use sockets and lights nothing has been specified all the client is saying i want this here here an here great fun

 

[Deleted member 26818]

You may have to provide high integrity earthing/terminations, if the earth leakage is expected to be high.

 

[IQ Electrical]

Bobby,

Your best plan of attack is to sit down with the client and draw up a list of anticipated connected loads, without this, we're just guessing.

It's easy to get carried away with clean supplies, filter sockets etc. but again it comes down to the use of the installation.

Also, if you are wiring ring final circuits, remember that as long as both cpc's are terminated independantly at all connection points throughout the circuit then this is deemed to be 'high integrity'.

Have a read through this guide:

 

[Golden_Boy]

the other loads are general use sockets and lights nothing has been specified all the client is saying i want this here here an here great fun

If you allow 3ma of earth leakage for each PC connected to a circuit and design accordingly, you should be OK.

 

[daniel hill]

If It is Going surface on dado ect could you get away with just on a mcb so you would remove the need for a RCD protection. i.e if you just have the sockets on the dado for the p.c / server On mcb
also in the past i think its stated in the regs that the server rack has to be bonded with a 6mm or 10mm bond
correct me if i am wrong

 

[malcolmsanford]

You only have to bond if there is a chance of them becoming extraneous conductive parts. Which I don't think a metal rack will become unless it's liable to have an earth potential.

I always think that we abuse reg 411.3.3 for sockets under 20amp that is under the supervision of a skilled or instructed person. I don't class an office full of IT people any of that. The reg IMO should be for industrial installations where you have a dedicated maintenace team.

There is no problems using RCD protection for equipment having high protective currents as long as you design the installation to take this into account. The old 16th if I remember right in fact advised that the current leakage should not be more than 25% of the rated I delta N which on a 30mA would be 8mA or rule of thumb was 7 to 8 items of equipment.

 

[IQ Electrical]

If It is Going surface on dado ect could you get away with just on a mcb so you would remove the need for a RCD protection. i.e if you just have the sockets on the dado for the p.c / server On mcb
also in the past i think its stated in the regs that the server rack has to be bonded with a 6mm or 10mm bond
correct me if i am wrong

Don't forget the socket rcd requirement for installations not under the control of skilled/instructed persons.

There is no requirement for bonding of server cabinets other than the usual regulations on bonding.

A figure of 15mA is quoted as a max regular leakage value on a 30mA rcd, I believe this figure is in the IET guidance on high integrity earthing.

 

[IQ Electrical]

Just seen Malcolm's post, apologies for any duplication!

 

[mogga]

Dado for the PC sockets allows MCB and gives space for cat 5 and expansion

 

[IQ Electrical]

This was the text from the IET on max background leakage:

As there is no testing requirement
between 0.5 I​

​

​

​

Δn and IΔn, it is fair to
assume that a 30 mA RCD could
operate at any level of residual
current greater than 15 mA. Therefore,
it would be pertinent to design high
protective conductor currents for
any circuit protected by an RCD
rated at 30 mA at a level no greater
than 15 mA. See Guidance Note 3 for
more information on the testing​

of RCDs.