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new2this

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Ive been asked by a friend to see how what would be required for a classroom of about 25 computers.
Was wondering what size cable and breaker to use, having not done comercial building before any help would be greatly recieved.
Thing you have to remember is its 25 comp bases plus monitors, thats 50 sockets. I said as a guess 10mm cable should be used! Help!
 
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ian.settle1

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Mentor
Arms
Ive been asked by a friend to see how what would be required for a classroom of about 25 computers.
Was wondering what size cable and breaker to use, having not done comercial building before any help would be greatly recieved.
Thing you have to remember is its 25 comp bases plus monitors, thats 50 sockets. I said as a guess 10mm cable should be used! Help!
You will have to put this over a number of circuits as if it is a school normally ring main circuits are put on RCD protection where I have come across them.

The reason for this is because with 25 computers the will be a high leakage current to earth thus causing RCD to trip.

Plus you would have difficulty getting 2x10mm into a socket terminal anyway:eek:
 
P

prideofengland

  • Thread Starter Thread Starter
  • #3
Also remember you are likely to have high protective conductor currents so use high integrity earthing or other method to comply with 543.7 BS7671.

As a guide on the RCD's Ive known as few as 10 pieces of IT equipment to take out a 30mA RCD, but newer equipment generally produces less leakage because of improved filters.
 
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tony.towa

  • Thread Starter Thread Starter
  • #4
Had a similar job about five years ago. Ran tails from panel board to a dedicated cu for the computer room, single pole mccb protecting tails. Three rooms done, three cus. Six ring circuits per room, run in three compartment dado trunking, data run in aswell. Each ring circuit protected by rcbo so problem on one computer does not take out complete classroom. School very happy with result.
 
K

KNIPEX

  • Thread Starter Thread Starter
  • #5
you would one hell of a job to put 2 10mm in a socket outlet connection.

as said before spilt the ring over a number of cicuits, will have to be on rcd aswell to conform to 17th regs

would say the same no more than 10 computers on one ringmain.
 
L

London Luke

  • Thread Starter Thread Starter
  • #6
you would one hell of a job to put 2 10mm in a socket outlet connection.

as said before spilt the ring over a number of cicuits, will have to be on rcd aswell to conform to 17th regs

would say the same no more than 10 computers on one ringmain.

even if you could get 20mm of cable into a terminal it would create so much pressure on the terminal frame and connector etc i imagine it would fail quickly
 
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jibspark

  • Thread Starter Thread Starter
  • #7
i dont know much about IT equipment but wouldnt you want some sort of surge protection and clean earth too?
 
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tony.towa

  • Thread Starter Thread Starter
  • #8
If you install a cu for the classroom a surge suppressor can be fitted onto the incomer. Nice little units are available now with three flying leads (L,N & E) and are relatively cheap. The requirement for a clean earth is unlikely in a school. The one I worked in is classed as a College of Technology and now has over a dozen computer rooms, direct link with County Council mainframe and feeds to all other schools in the town. There is not a clean earth there.
 

ian.settle1

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Mentor
Arms
From my earlier post and what others have said you may be biting off more than you can chew:eek:

Not only that before you can do the job you will have a CRB check because you will be working near children.
 
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S

Shakey

  • Thread Starter Thread Starter
  • #10
From my earlier post and what others have said you may be biting off more than you can chew:eek:

Not only that before you can do the job you will have a CRB check because you will be working near children.
Ian, when did he mention working near children?

Adults use classrooms too!;)
 
M

MRES

  • Thread Starter Thread Starter
  • #12
Solution

route through tool box for junior hack saw

ahhhh......junior hacksaw

lob off a few strands :eek:

perfect fit :cool:

however unable to fasten socket back due to cable size

route through tool box to find lump hammer

smash each socket back with brute force :eek:

Job well done !! Note to self .. bring along NIC inspector on next visit, this will really get me some browny points. :D
 
W

wayne

  • Thread Starter Thread Starter
  • #13
you forgot to mention silicone sealant to hold it all together
 
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tony.towa

  • Thread Starter Thread Starter
  • #14
This is not the first time you've mentioned silicone sealant Wayne. Have you bought a job lot of it??????
 
W

wayne

  • Thread Starter Thread Starter
  • #15
no i just seen "bodgit and scarper"use it once or twice .never touch the stuff personally.



except for sealing outdoor lights
 
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tony.towa

  • Thread Starter Thread Starter
  • #16
The favourite down here at the moment is putting surface mount patresses on with "No Nails", works wonders fo rthe plaster when you try to get it off!!!
 
Solution

route through tool box for junior hack saw

ahhhh......junior hacksaw

lob off a few strands :eek:

perfect fit :cool:

however unable to fasten socket back due to cable size

route through tool box to find lump hammer

smash each socket back with brute force :eek:

Job well done !! Note to self .. bring along NIC inspector on next visit, this will really get me some browny points. :D

I personally wouldn't use a lump hammer unless the sockets were metal clad. A far better solution is to open up the screw holes on the socket, drill through the backbox and then use these http://www.screwfix.com/prods/17637/Fixings/Shield-Anchors/Shield-Anchor- Stud-Type-10-x-125mm-Drill-Size-16-Pack-of-5 to pull the plate back to the wall.
 
J

jibspark

  • Thread Starter Thread Starter
  • #18
or a nail gun?
 
C

Carter

  • Thread Starter Thread Starter
  • #20
... is putting surface mount patresses on with "No Nails", works wonders fo rthe plaster when you try to get it off!!!
I call it "No More Brains" seeing as its use requires none. Just had to destroy three tiles to fish out the end of an open ring behind the partition wall of a "professionally installed" kitchen (18mths old!) box had been "fixed" with half a tube of this jizz! Part P? Laugh? I nearly filled me socks!
 
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old dog

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Arms
take a look in the osg high integrity earthing pages 66/67
 
N

new2this

  • Thread Starter Thread Starter
  • #22
Hi,
thanks everyone for your help, and those that just took the p*ss thanks for the encouragement. Think I have this sorted now. Im sure you will have a lot more questions from me in the future.
Thanks
 
H

hughesy

  • Thread Starter Thread Starter
  • #23
Ian, when did he mention working near children?

Adults use classrooms too!;)
I also think on a big job like this it would be done out of hours or in their holidays not when classrooms are full.
 
I also think on a big job like this it would be done out of hours or in their holidays not when classrooms are full.
Nothing more distracting during double history than a sparky standing on a desk, complete with dirty boots changing a light fitting.

(oh dont mind me, just pretend im not here)
 
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