How Many Sockets

[ALiEN]

Hi,
I'm fitting a new ring main and im trying to find out how many Double Gang 13A sockets I can put on a ring main, what gauge of cable to use and other considerations I need to consider.

The installation is for a ground floor (1 room) computer room and the cable will be run in a DADO rail. In total 28x2g sockets are required.

Only PC equipment will be used in the room

If anyone can advise me... Thanks

 

[AdamW]

28 double sockets? For a computer room? This sounds like a school. Are you insured to do electrics for remuneration?

Seriously, if this is a school or business then you shouldn't be doing this unless you have public liability insurance for doing electrics. I doubt you will have this unless you are a qualified electrician. In which case you would know the answer.

If this is your own home, then I apologise, just the 56 plug sockets made me jump!

 

[andy]

dont forget bout the earth leakage and earthing arrangements

 

[Damocles]

Um, just how much power is that exactly? Have you added up how much power will be needed? In general you can have as many sockets as you like on a ring. The question is how much power you need. 32A. If it comes to 31.9A, then I think you want more than one.

 

[AdamW]

Well, I would assume that seeing as this sounds like a school, 28 double sockets probably means 28 computers. Now, an average computer PSU is rated to generally 250-300W. A 17" CRT monitor draws about 90 watts. So, that is a peak power draw of let's say 350W (these PCs are unlikely to be loaded up with hard-drives or multiple processors).

(350/230) = 1.5A per computer

(350/230) * 28 = 42.6A.

So, you need 2 rings at least. Bear in mind a classroom with 28 PCs will also be likely to have a scanner, a laser printer and a projector: 100, 500 and 250 watts respectively. That adds another 4 amps or so to the total power draw, which still keeps it within the limit for 2 rings.

However, there may be technical reasons why it is better to have more than 2 rings. For one, it may make wiring the lot up easier. Fault-finding will certainly be easier with fewer terminals to be checked on each circuit. Many computing classrooms are arranged in a square W-shape. In this case it might be best to have a ring down each side, and one down the middle run in floor boxes or in a half-height stud wall.

I make the assumption it is a classroom as that is the only conceivable reason I can imagine you would want so many sockets in a room to be used for computers, without hiring in an industrial/office electrician to do the work.

 

[supersparks]

most schools where i am would use one plug per PC and use a splitter cable/ loop in/loop out power supply so thats 56 computers

 

[Damocles]

My pc and monitor is currently running at 173 watts. Bear in mind there will be a current surge when swithed on, so don't have them all set up with one big switch.

 

[AdamW]

What, like the big switch in "The Rocky Horror Picture Show"?

Thinking about this further, my school had UPS systems for the computers. Is this the plan with this computer room? If so then that will probably put some constraints on the design.