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daunavan

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I need help purchasing a UPS

I need a UPS that can carry the load of 4 Dell Power Edge 2950's for roughly 4 minutes. Any assistance would be greatly appreciated. Thanks.
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zzx999

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Most UPS manafacturers have size selector calculators this one is from APC

http://www.apc.com/tools/ups_selector/
PS, I have a 2950 on an APC 2200 and it has run for over 45 mins.  I would "assume" you could put 4 on for 4 mins, but I'd recommend you do the math using the tool I provided...
We run the APC UPS 1500 (rack - 2U) and it handles the load well.   Got to keep the batteries up.
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badgermike

You could get all down and dirty with the math however:


Have you tried using the APC selector?

http://www.apc.com/sizing/selectors.cfm 

You can chose your 2950's and then choose the run time - I did that for four 2950's (however I am not sure your exact model PE2950 or PE2950III ..or which processors you have) - it came up with 2000 total watts (just under 500 per) and said I could use a 2200 VA UPS...I would personally go a bit bigger because the maximum wattage per 2950 is around 750 (keep in mind that is a maximum and it would rarely ever use, but your servers depending on configuration could be running more that just under 500 watts (althout they may not unless you tested actuall wattage). I would be looking for 3000 VA ups just too be safe...

This one: APC Smart-UPS XL 3000VA RM 3U 120V shows a runtime of 8 minutes and 70% capacity with the 4 PE2950's...

 You don't have to go with the APC ups either, just find something 3000VA that is appropriate for you configuration.

Of course all this is assuming that it is just 4 2950's ..no modems, monitor, router etc.. plugged into the UPS.
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General note for UPS, look at PF power factor of the UPS
"Power factor is a ratio defining the relationship between use able power in Watts and total supplied power in VA (Volt Amperes). The power factor imposed by a load on a UPS system can be either lagging or leading. Traditional data centre loads have been lagging, but blade servers, which impose a leading power factor, are becoming increasingly popular because of their dense and flexible processing power. The closer the power factor is to unity, the greater is the power efficiency of the UPS operation." stated in http://www.upspower.co.uk/ups-products/choosing-a-new-ups/ups-technical-glossary.aspx

It means if you buy a 30 kVA UPS designed with a .8 power factor, in reality you are buying the equivalent of an 24 kVA UPS so you pay for a 30 kVA UPS, but in reality, with the load approaching unity power factor of 24 kVA, i.e. only 80% of the UPS
http://shop.1asecure.com/prod.cfm?ProdID=368732&StID=10715

refurbished - look for other refurbs - make sure you get fresh batteries

http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=SUA3000&total_watts=50

make sure you have a 30 amp feed

for redundancy buy two - one ups for each power supply

this should handle power backup for 10-15 minutes - for more add external battery packs

load these in the bottom of your racks - they are very heavy

careful -

10KVA is overkill

no redundancy
what do you mean , no redundancy?  It has redundant battery packs, and If required for capacity or redundancy, can easily be expanded by paralleling units. Up to four units can be configured in parallel without the need for an external control cabinet. For even higher power requirements or redundancy a total of up to nine units can be paralleled to supply the load.
what happens when you have to unplug the server from the ups to work on the ups?

2950's have two power supplies - power supply 1 gets power from ups #1 and power supply 2 gets its power from ups #2.

this gives you redundancy all the way to the breaker in the power box.

if the 10KVA unit has to be taken out for service all your servers have to go down.  unless you have those swanky bypass units that leave you unprotected while your ups is out of service.
well, all standard servers tday has at least two power suplplies. (bigger ones have more ;)
So:
1. I Never plug server just to one power source. (one to ups, other directly)
2. If you have a lot of server you have not only one ups. So can plug different power suplies to different ups
3. Some places have redudndant power suply from different grid stations. (use special relay switch, for redundancy) (anyway ups is needed in this case)

So you never need to shutdown server unless total power loss, and if so - ups is helping just for clean shutdown.