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View Full Version : Power requirements - how do I figure out what I need for future growth?

eSDee
07-09-2007, 03:35 AM
Hey everyone, does anyone have experience calculating how much power is required for a certain number of pieces equipment? I need to request a new circuit(s) for a server room that I am moving some equipment into. What do I need to calculate how big of a circuit is required? It's been a long time since I worked so closely with power. Any insight is appreciated.

Thanks!

Jeffbx
07-09-2007, 07:49 AM
First thing to do is calculate the amount you're currently using, usually in VAs or kVAs. On the back of each machine you'll find a power rating (or you may have to dig it up in the documentation). It'll look like this:

110-240v 4-8A

That means on a 110v (120v here in the US) circuit, the device will pull 8 amps. 120x8 = 960VA, or .96kVA.

So, for a normal 15Amp circuit, you can safely plug in 120x15 = 1800VAs, or roughly 2 large machines or maybe 3 smaller machines.

Be sure to look out for larger equiment that may require 220 voltage or higher than 15Amps.

Once you add up everything you CURRENTLY have, add in everything you're PLANNING on adding. Don't forget air conditioner units, lighting, spare circuits, etc. Once you have everything figured out, take that number and double it. Planning on being there for more than 5 years? Double it again. Now you'll be safe for a while.

Hope that helps!

DarkFury
07-09-2007, 09:04 AM
Ooops... neva mind.

I saw that you were talkin' about power circuits ... not power supplies. My bad. :D

eSDee
07-09-2007, 12:50 PM
Jeff, yes that does help a lot thanks! This is the specs of one of my servers:

Redundant load-sharing hot-swap power supplies (450W); universal input (100V to 240V AC), power factor corrected
Maximum input current: 7.6A (100V to 127V) or 3.6A (200V to 240V)
Power usage: 300W typical continuous power, 400W maximum continuous power
Dual DB-9 serial ports for UPS systems
Frequency: 50Hz to 60Hz, single phase

This is pretty close to what you posted. Does that mean that if I wanted to have 10 of these computers, I would have to have 5 independent circuits to power them?

Thanks!

Jeffbx
07-09-2007, 03:31 PM
Yup - I'd say a max of 2 of these per 15A circuit. If they're dual power supply, I'd recommend mixing circuits - so on machine A, plug one PS into circuit #1, and the other into circuit #2. Then in case you blow a circuit, the machine still won't go down.

The nice thing about dual PS is that it's still only pulling the load of one PS, so essentially you can have 4 power supplies (but only 2 machines) still on a single circuit.

eSDee
07-09-2007, 04:33 PM
Thanks a lot Jeff. I owe you one buddy :cheers: