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Crackrack power supplies

A

Athlex

Golden Member
I've got a power supply question- how much power do they really draw?
I've got 6 power supplies on one 15 amp circuit at home.
1 300W ATX -- Athlon
3 250W ATX -- 2 Celerons, and a Pentium
1 220W AT --- Pentium
1 100W R-AT - K6-2
So that totals 1370 watts, ~12.5 amps at 110v. Do the motherboards only draw as much as they need or am I on the verge of popping a circuit breaker?

<edit>typo correction</edit>
 
I have twelve 250W power supplies plugged in to a 20 AMP breaker, and it has no problems at all. I did have 15, but adding just one more device would trip the breaker, so I put the other three (two servers and my build bench) on a different breaker.

That should give you an indication where the critical point will be. I'd say you have room for two more before you need to be concerned.

Russ, NCNE
 
Athlex
Your fine, and yes the powersupply will only pull as much power as it needs.🙂

Your calculations are not correct. I did the same thing before it hit me. The wattage rating on the power supply is the DC output power. Not the amount of AC power it's pulling.😱

Some power supplies will tell you the max amperage it'll pull. For example I have 2 145w power supplies and one states .5 amp max current @ 115v while the other is 1 amp. Even though they both have the same output power one is more efficient and pulls half the max current as the other. Most power supplies are going to pull between .5-1.5 amps of power.

Take Russ's example on a 20 amp circuit:
12*1.2=14.4amps
15*1.2=18amps

Keep in mind that according to the building codes a circuit shouldn't continiously pull more than 80% of it's maximum rated load.

20 amp circuit=16 amp continious
15 amp circuit=12 amp continious

BTW keep in mind to consider anything else that's on the circuit with the computers.🙂

 
Glad I don't have to worry about killing my machines if I hit the light switch. 🙂 My goal for the time being is 8 racks (limited by room, power, KVM switches...), so that works perfectly.
Thanks for the help, guys.
atx
 
Oh yes. Can't wait until I can get a digital camera, then comes the website. I'd also like to follow that up with a TA pProxy if broadband ever makes it to where I live.
I've almost regressed from treating computers like a gameboy to just treating them like calculators. 😀
 
Back in the days of WarpCore, we had 10 dual Celly 300a nodes running on one 15 AMP circuit. This ran it fine as long as the AC power didn't have a &quot;dip&quot;.

I never had a tripped breaker with 8 or less dual nodes online at one time.

If I remember correctly, there is a power consumption calculation page somewhere on the old WarpCore site. (we built a box to specifically figure out the draws from each component).

Of course I was using 145W power supplies and only boards, procs, FDD, coolers... no PS or monitor per node.... 😉
 
Hey Russ, you mentioned that it's possible to run power supplies without their fans on. Does that go for most powersupplies or did yours have beefier internal heatsinks?
 
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