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Reducing the inital high power requirement when turning on

I

iniazi

Junior Member
Ok, basically I have a co-location rack with 20A of power. And it turns out I can only use 16 to 17A before tripping the circuit breaker (I don't understand why really but whatever). I'm using about 9A now. I have a storage server that I'm putting in this rack (24 750gig drives machine, and dual dual-core opteron etc.) that uses 11 amps when it powers on. It uses that much for about 5 or maybe 10 seconds, and then almost immediately goes down to about 4.5 amps.

I can handle the 4.5A sustained power, but its the spike to 20 amps that I can't. I was thinking that if I put a UPS in the rack and connect the storage to that (all four of its power supplies), will the battery absorb the load? Or since the UPS has power, will the extra load be just passed down, defeating the inteded purpose?

Oh the server has two SuperTrack EX16300 controllers, which might not be that great. Anyway, I don't think they support staggered power on, or atleast I don't see an option in their POST config tool. OR i guess I can buy a different controller but it will still probably have a power draw of 7 to 8 or 9A. Anyway some of the cheaper 1U or 2U 1500 kva UPSes are like $200 or 300 (I saw one at Frys i think). I'm just trying to keep the costs down etc. and I'd rather not pay another $200 or $300/mo for an additional 20A drop.
 
Pay the money for the drop or switch out the controller for one that supports staggered spin up. Using a UPS might work in the short term, but it would not be a reliable setup. If your are going to pay $200 for a UPS, why not just pay $200 to get someone to install the proper wiring.
 
Well its not a question of wiring, its the question of the expense. Another 20A is $3000 or 3600/yr. Or I can replace the controllers, I guess 24pt controller or two controllers... etc. will set me back around $1500. But not sure if the staggered spin up will mitigate the power draw by much. Just isn't a good time, financial wise. But I guess I'll just have to get a bigger power circuit. Also was wondering why the UPS isn't a reliable setup? Will it even work, i.e. absorb the larger power draw?

Thanks for your input.
 
The UPS isn't reliable for this because a UPS is designed for loss of power at the wall side not for power drop caused by the devices powered by the UPS itself. It would probably not even come on in that situation unless the wiring inside the wall is so small that when you exceed its rating the voltage drops below usually 108 volts.

Staggered spin up will decrease the power by a lot since it only spins up one drive at a time. Then moves on to the next drive.
 
Ok, Cool thanks. yeah thats what I needed to confirm about the UPS. I talked to the Datacenter folks, and they said it will trip at 20A, so I MIGHT even be able to get away with this setup. 16A is the recommended maximum.

But I'm going to have to just look for a 24port controller or maybe a 16port one that I can join. Off to google controllers...

Thanks again!

 
Have you tried replacing the breaker itself? Once a breaker is tripped the first time, I have heard that they will trip easier from that point forward. But, I don't mess with AC much so I can't verify that from personal experience.
 
I don't see why you couldn't unplug the UPS (starting with a fully charged battery of course), boot up your equipment, and then plug the UPS into the wall socket once everything is up and running at 4.5A. Not sure I'd do this on a daily basis, as it would be really hard on the UPS, but I imagine a storage server is going to be on 24/7/365; cold boots would be few and far between no?
 
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