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Re: Electrical design for Server room [Re: gfretwell] #190467 11/19/09 11:33 AM
Joined: Sep 2002
Posts: 888
NORCAL Offline
Originally Posted by gfretwell
I see this is California. In Northern California he might get away without a whole lot of A/C if he just ventilates the garage. The energy police might like that better. PCs are really a lot tougher than the "computers" of old. They don't need that "glass house" environment. I have had one in my car for almost a decade, cranking up at 120f or so whenever I get in the car in the summer. There is also one that has lived in my garage for almost as long, including surviving a fire.

Your kidding? grin In the Sacramento Valley in the summer temps can run in the triple digits for days, the one advanage of the Sacramento area is that the Delta breezes cool things down at night.Death Valley it's not, but it's quite hot in the summer here.

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Re: Electrical design for Server room [Re: gfretwell] #190468 11/19/09 12:23 PM
Joined: Aug 2002
Posts: 402
jdevlin Offline
It is never recommended to HVAC on a UPS. Some room ventilation fans maybe but not HVAC. The servers will survive the time it takes for a generator fire.

The only way to maintian service in a power interuption is a UPS. For extended outages you add a generator.

Re: Electrical design for Server room [Re: jdevlin] #190472 11/19/09 01:35 PM
Joined: Jul 2004
Posts: 9,452
gfretwell Offline
Sorry Norcal, For some reason I thought it was cool there.
My mistake.

Greg Fretwell
Re: Electrical design for Server room [Re: gfretwell] #190475 11/19/09 02:50 PM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline
Cat Servant
But Norcal, it's a DRY heat. laugh

Jdevlin, that is a very good point about the HVAC. Thank you.

This is one of those times where we really are not getting the complete story - as suggested in the elaborate plan I had suggested. Next thing you know, the OP will be back asking about COPS wiring methods. laugh

Re: Electrical design for Server room [Re: renosteinke] #190477 11/19/09 03:06 PM
Joined: Jul 2004
Posts: 9,452
gfretwell Offline
My point was, before we get too far we really need the actual load. Then you size the HVAC to the sensible heat from the hardware, plus the latent heat and the room load.
I agree you don't need the HVAC on the UPS if he is going to have generator backup.
Are these 30 servers redundant access to the same system or do they all need to up? That can make a difference too.
In real life, if he wants his availability to be anything in the "nines" he should have an alternate site. There is just too much that can happen in a system with a single point of failure like that. (Earthquake, flood, fire, criminal mischief etc). The biggest single point of failure is probably his broadband carrier anyway.

Greg Fretwell
Re: Electrical design for Server room [Re: gfretwell] #190628 11/27/09 04:38 PM
Joined: Sep 2003
Posts: 114
bwise121 Offline OP
Just a follow up. The customer took one look at the price of a gas fed 10kw generator and automatic transfer switch and has opted for a manual transfer switch and to purchase a tandem Honda generator set up.

The Servers are basically old PCs. I have put it on him to figure out if the UPS system will suffice. I've been told that even with those installed there will be a flash in the power supply. I'm not sure if that causes a problem for his PCs or not.

It seems he is on a rather tight budget, who isn't these days.

Thanks for all your thoughts!

Re: Electrical design for Server room [Re: bwise121] #190641 11/28/09 02:44 PM
Joined: Jul 2004
Posts: 9,452
gfretwell Offline
I have regular old APC UPS's on my PCs and they work fine. The PCs handle the switching glitch OK. If he keeps fresh batteries in the UPS (replace about every 3 years) he will be able to count on about 80% of the rated capacity. That should give a reasonable reliability if the system is attended but it sounds like a one man band operation so a power cut at 3 AM may bring him down if he doesn't wake up, start the genny and flip the transfer switch.

Greg Fretwell
Re: Electrical design for Server room [Re: gfretwell] #190756 12/03/09 02:48 PM
Joined: Mar 2005
Posts: 1,213
SteveFehr Offline
I was going to chime in about the benefits of using a central UPS over small rack-mount units, but if he's just going with an MTS, he's probably not going to be able to do it "right".

Unless these are massive industrial blade server chassis, he doesn't need a 20A circuit for each server. It depends on the type of server, but if they're just PCs being used as servers, they probably draw around 1-2A each. My advise is to put a clamp on there and measure the current, and then buy a SINGLE UPS to power it all. Use the UPS to supply a panel, and feed all the servers from there. KVM and monitors and all do not necessarily need to be on the UPS, but it it's helpful if you have to shut them down when your gen doesn't start. HVAC should NOT be on the UPS, nor should any printers. E-lighting: yes. Normal lighting: no.

If he's on a dime, there are vendors that sell used UPS systems and would be pretty reasonable for a larger system. (I bought a used parallel-redundant 50kVA Powerware system last year as a training UPS for a ton cheaper than buying a new one- if you don't need five or six 9s, you can get away with it.) He's probably only looking at a non-redundant unit somewhere in the 3-5kVA range for 30 PC-based servers. If he can't afford a 10kW generator or an ATS, he's probably not going to be able to afford an UPS, either. He might want to scale down his plans a bit.

On the other hand... 350VA APC Back UPS can be had for about $30 on sale. And a 3kW gen at Lowes for $400.

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