[Beowulf] powering up 18 motherboards

Eric Machala emac at cybergps.net
Thu Feb 17 23:36:34 PST 2005

This is not true the Ups will not draw ever any more from the wall that its 
is set to, ups has a set trickle rate that is able to be set  to a cost 
effective trickle rate unless it is load overloaded it, if this is the case 
it is double the trickle rate becuase systems wants to restore full battery 
before power drain err loss of power.... i could get the actual specs on 
this but for your actual needed load if u were in a 50-65% load im sure 
there would be no spikes in power draw over normal trickle
----- Original Message ----- 
From: "Alpay Kasal" <eno at dorsai.org>
To: "'Jim Lux'" <James.P.Lux at jpl.nasa.gov>; "'Dean Johnson'" 
<dtj at uberh4x0r.org>
Cc: <beowulf at beowulf.org>
Sent: Friday, February 18, 2005 12:43 AM
Subject: RE: [Beowulf] powering up 18 motherboards

> James Lux, thanks for the extremely useful explanation. Btw, I'm in
> Brooklyn, NY. 120volts, 60cycles, regular AC power. I don't know the gauge
> of the wiring in the walls but (as mentioned in another response just now) 
> I
> suspect it is old wiring and is the reason for the strange 10amp circuit
> breakers.
> I looked at the x10 modules. Seems like it could be very useful, just 
> script
> all of them from my headend. For now I'm going to try to handle the 
> power-on
> sequence myself. I figured I could steal 3 10amp circuits from the house.
> Follow me... Turn on 4 nodes (on 1 strip) which will peak at 5.2amps. let
> that settle down to a steady 3.48amps and hit another strip of 4 nodes.
> Total draw while the 2nd batch is starting is 8.68amps. It should steady 
> at
> 6.96. I then have room to turn 1 more node on. Then one more after that. A 
> 4
> step process to get 10 nodes powered up without going over 10amps. Perform
> the same exact steps on a 2nd circuit. Annoying but possible without
> spending anymore money.
> I was really hoping a decent $200-300 UPS would come to the rescue here. 
> Oh
> well.
> I just had a thought... I planned on making use of wake-on-lan. I can just
> start sending jobs to the whole network though if all of it is asleep, I'd
> have to still be careful of the powerup-sequence. Grrrr. Maybe a script to
> perform WOL before starting any number crunching.
> Boy did I take nice big fat electrical lines for granted in the past!
> Alpay
> -----Original Message-----
> From: Jim Lux [mailto:James.P.Lux at jpl.nasa.gov]
> Sent: Thursday, February 17, 2005 7:18 PM
> To: Dean Johnson; Alpay Kasal
> Cc: beowulf at beowulf.org
> Subject: Re: [SPAM] [Beowulf] powering up 18 motherboards
> No, the UPS won't help.  It might make things worse, because as you flip 
> on
> all that load, the voltage will sag, causing the UPS to turn on, which 
> then
> might trip from the overcurrent (assuming you're not out buying a 2kW 
> UPS).
> You could use the X-10 type (aka Plug n Power) remote controlled relays
> (don't use Lamp modules.. you need Appliance modules, which are relays
> inside).
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