How many servers is it safe to connect to a 15 amp circuit?

[Mucman]

I do not want to overload the circuit but we have some Cubix machines which have 8 computers inside of them and other servers like this and was wondering what the general rule of thumb is...

 

[ttn1]

It totally depends on the power requirements of the individual servers. It probably would be a good idea to measure the current
draw of the Cubix machines. If they are especially power hungry, you might have a problem. I would guess that the average
single processor server would draw about 30 Watts continuous power. But this is definitely dependent on the number and type of
drives and other peripherals. This would yield something along the lines of 87 processors. But I would give myself a hefty safety
factor and say that you really shouldn't put more that 30-40 servers on one 15 amp circuit.

Mind you this is only a guess, you might want to wait for more replies. To either backup or dispel my guess.

 

[cipher00]

(I hate this 'cuz I usually get this wrong...isgust

I think it's something like: amps * voltage = watts

So, at 15 amps, how many watts are you trying to draw, over what I'll assume is a 120v circuit? You've got 1,800 watts to play with, though being well within that band would be advisable....

I put in 20 amps just for my desktop & assorted nonsense... printer, router, speakers...

 

[Mucman]

30-40 on a 15 amp circuit? That sounds high to me, but I really don't know what is appropriate.

When you are talking about watts, the draw of a PS isn't 300W for a 300W power supply , right? Doesn't the 300W stand for the peak output if you had 8 drives and other junk in there?

BTW, I am asking this because a breaker on the power bar went... It had a Cubix (8 machines) and about 6 other machines attached to it. The power was fin for everything else in the room so I was starting to think I had overloaded it.

 

[Vegito]

I have 4 15 amps circuit in my server room, each on sits a APC 3000 RM which supplies power to 2 server each. Each server has 3 300 watt redudant power supply.

That'll give it enough power for 1 extra hour and believe me, I tested it up to 1 hour 10 min when new and around 59min a year later..

 

[Becks2k]

300W is the max it can supply, it isn't 100% effient, its bout 70%... so if it ever does put out 300W its sucking 428watts.

The avg cpu I'd say draws a constant 100w... ~40 for the cpu 30 for hrte mobo and pci cards 10 for each harddrive... if the cpu is 100% load all the time it'll use 50-60 if its a fast athlon or something... I dunno you can think it up on your own 100w isn't that far off imo....
so thats ~140w your powersupply is drawing

15amp@120v = 1800w

1800/140 = 12.8

thats with no monitors on... each of those is around 100watts, but servers i'm doubting montiors

13 computers for 15amp.... if you turn them all on at the same time it'll blow the circuit

So 8 isn't bad, best would be to measure tho.

thats just my opinion.

 

[Mucman]

Thanks for the tip... This will be some good knowledge to have when we have 1u or 2u cases which would mean we could put 20 or so on a rack (guesstimate).

btw, the Cubix machine with 8 computers (not CPU's) in it only has 3 power supplies. Anyone have any pix of one opened? Due to warranty and customer wishes, we
do not open out co-located customers machines unless told to