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How many computers can i plug into one power outlet?

Discussion in 'Electronics & Electrics' started by ChEEkY ChiNo, Jun 1, 2003.

  1. ChEEkY ChiNo

    ChEEkY ChiNo Member

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    Im thinking of having a LAN but i dont no about the power thingos and how much computers my house can handle.

    What im trying to say is "How many computers can i plug into one power outlet (wall outlet)? "

    Ive got one 15amp plug in my garage and all the rest in my house are 10amp. Whats the most ammount of computers i should put into each power outlet.

    Say basic computer, 17", 2.6Ghz, 80G HDD, 52x Burner, 64Mb Graphics etc etc....
     
  2. psiaxis

    psiaxis Member

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    if you allow 1amp per computer you should be fine, making that 10 pcs from the 10amp sockets and 15 from the 15amp socket. by doing that you are playing it safe. if its only a small lan tho spread it out and have no more than 5-6 pcs per point.


    hope that helps a bit
     
  3. ViPeR-7

    ViPeR-7 Member

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    from experience, an xp2800+ with gf4ti, 1xhdd, 19" monitor, and all the other junk, uses around 0.8 - 0.9A.
    a general pc (ie 1800mhz, 17" monitor) will use about 0.5-0.6A

    ALWAYS budget for at least 1A per pc though, as pc's and both fuses and trip switches kinda disagree...

    you also have to look at the circuits, if you have 3x10A power points around the house, you cant necessarily draw 30A from them combined, as they may all go though the same 10-15A breaker. an easy way is to get a mate over, plug a lamp into your power socket, and turn the breakers off then on in order until the lamp turns off, once it does, leave that breaker off, then move the lamp to every power point in the house and see if there are any other points that dont have power anymore. if you have fuses.. then... sux2bu =)

    also keep in mind this will reset any electronic clocks / computers in the house.

    ive also often been in the frustrating situation of having a 20A breaker, with only 1x10A point in range.

    never overload the points, it just aint worth it.

    also, double power points are rated each, so if you have a double power point with 10A on it, you can draw 10A from EACH of the 2 points. but again, only if your circuit breaker / fuse allows it.

    otherwise, dont chain powerboards, plug one large one into the power point, then all plug your powerboards into that, use a double adapter if you must and run 2 powerboards from the socket, but try not to have more than 2 powerboards between a computer and the power point.
     
  4. Sinizterguy

    Sinizterguy Member

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    Coming out of one socket, with a lot of extension cables and stuff, I have

    • 1 x Toshiba 1.6 GHz P4M Laptop
    • 1 x Shuttle System - 2.53 P4 @ 2.67
    • 1 x Athlon 1600+ System
    • 1 x Athlon 2400+ System
    • 1 x Toshiba P3M 1 Ghz Laptop
    • 1 x Celeron 400 MHz
    • 1 x Toshiba Portege 500 Mhz
    • 1 x Creative Extigy
    • 1 x Creative DTT3500 Digital Sound System
    • 1 x Samsung 150MP 15in LCD
    • 1 x 8 port 10/100 Switch
    • Loads of adapters for stuff like digital camera, 2 mobiles
    • 1 x HP Laserjet 1100
    • A desklamp
     
  5. star882

    star882 Member

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    1 amp per PC is reasonable for a small system(120w), but most PCs use more.
    BTW, My friend Christina Mahoney had a problem with tripping breakers recently.
    She had a dual processor(2x 2.2GHz Britney IIRC) machine(the circuit simulation workstation(she designs and builds SMPSes)) on a 15 amp circuit.
    Everything went well until she plugged in a hair drier into the same circuit, which tripped the breakers(thank god for UPSes).
    Only 108 watts(0.9 x 120 = 108)?!
    That doesn't sound right.
     
  6. AdeptaCheese

    AdeptaCheese Member

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    it depends on how many computers and powerboards you want to fry.
     
  7. zzzzz

    zzzzz Member

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    We use 240V in Australia so a 10 amp circuit can support 2400W. P=IV, watts=amps*volts.

    I'd allow 300W/computer incl. CRT monitor ie. 1.25A/computer. So no more than 8 computers/circuit.
     
  8. D F

    D F Member

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    That is a useless statement. Powerboards or extension leads don't instantly explode in a shower of sparks and smoke as you might of seen on TV. The only current limitation there is on a conductor is the amount of heat it can safely dissipate before the dielectric starts to melt and fail causing the conductors to fuse. Then, you will see spark, but the circuit breaker or fuse will trip protecting that circuit. You will see on most cords, there is a temperature rating of the plastic. If you don't exceed it, you are fine. Any computer that was connected to this will see a drop in voltage (almost zero) during the overload condition, then total loss of power. The computer will not get 'fried'. This is hardly the case ************ Read carefully from now on, since this is unlikely to happen due to ones lan party escapades:
    You may head of such a thing called 'load dumping', which is when a large electrical load is removed from an electrical system, which then can cause a surge. I mean large in comparison to the local step down transformer. The back EMF of the transformer will cause a spike in voltage once the load (typically an overload condition) is removed. This can happen if say a paraglider gets tangled in the over head wires outside you house. The conductors will touch periodically, causing a large current to flow. This increases the magnetic field strength with the transformer core jumps, if the load is removed (the offending wires will melt) the collapsing magnetic field will produce your spike, which might 'fry' your computer. But if its some measly 10 amps extension cord, the magnitude of the overload would not be significant enough to produce a spike.
     
    Last edited: Jun 1, 2003
  9. slavewone

    slavewone Member

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    I like this answer, allows you 8 on the house circuit and 15 in the garage - assuming noone uses a hairdryer.electric kettle etc.

    You should find if you have electric appliances like stoves/hot water systems(non of peak)/somtimes fridges and pumps ("pool") - they sometimes use seperate circuits that you "might" be able to use.

    If i did that, there are 5 circuits i could/would use (with my limiting factor being the length of the extension cord - can't reach any more)
     
  10. D F

    D F Member

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    the limiting factor would be the capacity of the service, 60 amps for most homes I think (for single phase).
     
  11. Gazavage

    Gazavage Member

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    hey

    considering i have run over 30 lans, none of which had power problems bar one (which was faulty equipment) i think i know what im doing. lol

    Basically, work on 1.5amps per machine as surge protected power boards/monitors/switchs/speakers etc etc draw lots more power.

    on 1x 10amp plug i wouldnt go any more than 7 computers to be safe.

    Check your meter box also. Have a look at the main RCD (residule current device). It that has a little thing on their "30ma leakage" then you could probably get away with a max of 20 computers as each computer has around 1.5ma of leakage.

    Also, your house is likly to be split up into seperate circuits - usually 2 or 3x 20amp power point circuits, 1x 10amp for lights and if you have an electic oven etc, 1x 30amp for that.

    What i would recommend for a 20 person lan would be to get 4extension leads and draw power from each corner of the house (most likly to be on different circuits) and you shouldnt have any problems.

    One more thing, dont piggy back power boards if you can help it - split the extension lead into two with a double adapter and put put the power borads in to that.

    Hope that helps and feel free to ask any questions.

    Cheers
    Gareth
     
  12. ledz

    ledz (Banned or Deleted)

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    check the rating of the power boards you are using as well...
     
  13. Symon

    Symon Castigat ridendo mores

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    NEVER use double adaptors if you can help it. The reason being is there is no overload protection in the adaptor. Powerboards are fine as they usually have inbuilt overload protection. AFAIK double adaptors are in the process of being banned in Australia, they already are on most commercial and industrial sites.

    Everything else that you said was fine though.
     
  14. D F

    D F Member

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    I use double-adapters, its the cheap way to distribute power. As well as having to worry about the CB's in the breaker panel tripping, you also have to worry about the ones in the power boards. So, this is what you do if you want uber cheap power distro:
    Buy a tradie extension lead, which actually uses 1.5mm^2 of copper. Then run that to a double adapter, and have 16 or so computers running of that. (with power strips) The result, the extension lead gets utilized 100% (cost effective), and you only use 1 extension lead per circuit, so you can still observe the 80% rule. And yes, I know you are going ot tell me how the plug is only rated for 10amps or whatever, the extra metal in the double adapter will provide extra heatsinking. Just make sure it doesn't get covered up with some clothing or something. And on the other end, use some sticky tape to support the cord to keep the weight of the plug- the extra heat will soften the plastic in the extension cord an cause the plug to deform> the power point plastic has a higher melting point however; and if its an old power point made with brittle thermosetting plastic, No worries. . just make sure that a: you can feel good electrical contact when you plug it in, and B: you don't break it.
    And the chance of a down right short is very low, every monitor and powersupply has a 2 or amp fuse in it, so if a computer is dodgy, it can fuck itself and blow its own fuse, while everybody else remains uninterrupted. (provided that there is no RCD protection of cource - another pain in the ass).

    And I disagree with the 1.5ma earth leakage / computer thing. There is 2 1nf caps connected between the active and earth in a complete computer system (one in monitor, one in PSU). I am ignoring the ones between the neutral and earth, since little current will flow because there is little potential between them anyway. I heave heard that its more like 80 Pcs before you get problems, and I concur.
    Xc = 1/ (2xpixFxC)
    so for 2nf/comp
    Xc = 1/(2xpix50x2x10^-9)
    =1.6mohm
    V=IR
    I=V/R
    1.5x10^-4 amps
    or, .15mili amps.
    that means you can get 200/30ma rcd. But in real life there is RF noise of higher frequency induced in the wave. When all the caps try to arrest that, thats when its toppled, such as arking of heavy switch contacts etc.

    As for this power strip business - In my opinion, I think its a load of BS. Does the physical shape of the conductors matter? The only thing is, is that if you get a group of mates, they will typically connect them selves to the power strip first, then connect that to the power source, powering up 3 or 4 computers at once, this creates lots of inrush current (possibly tripping the main breaker), and if in mid cycle, the 1nf caps will also create a little earth leakage inrush, tripping the RCD. Convince me otherwise.. I have been to lans now, where the people there have no idea.. I end giving them advise on how to run things..



    IF your that pussyfied, get the RCD power points, and make a power stringer to service 20 people and use only 4 power points, but make them RCD. Then, get 2 powerboards per power point and point them out in opposide directions. What totally sucks is using those intergrated RCD/20 amp breakers, you dont know if its an overload or earth leakage..
     
    Last edited: Jun 1, 2003
  15. Symon

    Symon Castigat ridendo mores

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    Yes, you may get away with using double adaptors, I have been using them myself for years without any problems. However, if you are hosting events open to the general public (like most LAN's) then you run the gauntlet if something did happen. It's just not worth the risk.

    If you use a tradie extension lead and run 2 power boards off it via a double adaptor, you can possibly be running 20A off that one lead. Yes, you are right that I am going to say that the plugs and sockets are not rated at that kind of current, and regardless of how much heatsinking you think you have, I still refuse to recommend it. I have seen a brand new 10A outlet melt when it had 12A drawn through it, they aren't as robust as you might think - remember, they are made to a price, and most BARELY meet the ratings standards.
     
  16. Autumn

    Autumn Member

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    go for the 10 pc's option. i've had lans at my place before and unless you want to turn of all the essentials like the fridge etc. then stick with 10 pc's.
     
  17. Yeti_Skinner

    Yeti_Skinner Member

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    If you get 60A for a simgle phase power system does that mean you get 180A for a three phase power system?

    Just wondering as we have 3 phase here and was wondering how much I would be able to run.
     
  18. D F

    D F Member

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    60 amps / phase, short answer yes, long answer probably not if you were using GPO circuits. Unless your house has 9 power circuits, (3 per phase, 20 amp each), I think you'll find that there is some level of inaccessible capacity on some phases, which is used by hot water heaters, fixed airconditioners, etc. But if you were dodgy and tapped every circuit, one way or another, then yes you could do it, but Check your neutral current if your running computers. I think you'll find that the non-sinusoidal current waveform of a computer doesn't cancel in the neutral wire completely, so watch it. There is no protection to stop you from overloading your neutral wire; However if your in a suburban area and use a water pipe as earth, some of the current will that path - get this, with the AC on, and some computers, lights, my house was pulling 14 amps from the grid. 2amps was returning via earth, even then we don't even have a solid connection to the pipe, its sort of only wrapped around and twisted.. So, there is lots of things to consider.
     
  19. Gnuthad

    Gnuthad Member

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    Unless you have had your cabling checked to ensure it can handle higher than 15A per circuit, do NOT attempt to exceed this rating. The average house uses 1.5mm cabling which results in a maximum circuit draw of only 15A (at best, lower in hot weather). In oder to achieve your desired 20A per circuit, you'll need to be running 2.5mm cable, usually reserved for water heaters, 15A circuits etc.

    Edit: Added the missing 1 to make 15A instead of 5A

    Just because some fool has placed a 20A breaker at the switchboard does not mean you can safely draw 20A through that circuit. Don't take the risk of starting a fire in your roof, get the cable checked by an experienced electrician before attempting to draw over 15A from the circuit.

    In my case, I am lucky in that all my cabling is done to 2.5mm standards, I can safely run 20A breakers at my switchboard without a problem. Of course, having the 60A service fuse sort of slows me down a little on hooking up an uberleet LAN, but oh well.
     
    Last edited: Jun 2, 2003
  20. Aaron_85

    Aaron_85 Member

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    1 - i dont know about other electricians in other areas but i know were i work and all the elctricians i know use 1.5 for lights and 3.5 fro power (which is 15 for 1.5 BUT i think its more like 25 for 2.5, but ill ask) we put 32A circit breakers on power circuts. (i think)

    2 - if the place catches on fire, and an enquiry is done and it is found that the fire was caused by an inccorect sized curcit breaker, the electricians gets his ass kicked bad, there shitloads of rules and regulations regarding the selection of circut breakers

    3 and the fact that by law you can only run a maximum of 63 amps per phase (189 sorta if your over 3 phasess) anything over that your fucked short of your own substation
     

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