Web Hosting Talk : Web Hosting Main Forums : Colocation and Data Centers : Liebert UPS Efficiency

[KarlZimmer]

Hello everyone,
I was wondering if anyone with some experience running facilities, etc. is familiar with how much power a 750kVa Liebert UPS will use when it is under minimal load. I am aware that power is needed for keeping the batteries charged, keeping the power levels consistent, etc. but what is that base amount? Then, at around full load, what efficiency levels can I expect?

If it helps, I believe the model # for the specific unit is FRUDA63750A36A3

[jayglate]

You get much better efficiency by going with 2 or 3 smaller units than 1 big unit.

[KarlZimmer]

Originally Posted by jayglate

You get much better efficiency by going with 2 or 3 smaller units than 1 big unit.

I know that much, but I'm looking at an existing facility and doing some base cost analysis, etc. as I want the space, but don't need much of it immediately. Wondering how much the 2 750kVA units are going to cost me on my electric bill.

[sailor]

Originally Posted by KarlZimmer

I know that much, but I'm looking at an existing facility and doing some base cost analysis, etc. as I want the space, but don't need much of it immediately. Wondering how much the 2 750kVA units are going to cost me on my electric bill.

35 to 50 kva per unit will be used with it just idling.

[Linn_Boyd]

Sailor hit it about dead on, you are going to need to also replace the batteries if it has been sitting for any amount of time.

-Linn

[Jay Suds]

If the units are currently running [with no load], take an ammeter over there and find out how many amps the units are pulling. Or drag your electrician over there with you, and let him do it.

[scapeish]

A quick question related to this thread but not covered within it; slightly off topic.

Is it industry standard to run the UPS constantly wth minimal load in order to prsever batteries, or would the extremely light load nonetheless drain the batteries chemical life (not the amount of power contained within)? Sorry for the off topic, but I'm hesitat to make changes before I have multiple industry experts' second & third opinions. Thanks for the reply.

[sailor]

Originally Posted by scapeish

A quick question related to this thread but not covered within it; slightly off topic.

Is it industry standard to run the UPS constantly wth minimal load in order to prsever batteries, or would the extremely light load nonetheless drain the batteries chemical life (not the amount of power contained within)? Sorry for the off topic, but I'm hesitat to make changes before I have multiple industry experts' second & third opinions. Thanks for the reply.

the load on the ups has nothing to do with the battreries per your application. when the ups is on and the battery breakers are closed it will keep them charged and give them a longer life.

the only thing that drains batteries and shortens life is:

unbalanced strings due to mix matching battery types and ages and or lots

leaving them in a state of discharge

not keeping them charged for long periods of time

not hitting them every now and then with a load discharge that will knock the dust of the plates (not really dust - its a buildup though)

[sailor]

Originally Posted by TheDingy

Sailor hit it about dead on, you are going to need to also replace the batteries if it has been sitting for any amount of time.

-Linn

that is correct. depending on the units age - you also might have to replace the ac and dc caps.

the dc caps are a little more tempramental - they will absolutely need to be replaced if the unit is 5 or more years old and they have not been replaced before.

you can usually call liebert and they can give oyu the service history or the guys taking care of it will usually have their sticker on it somewhere.

both can be expensive.

also visually inspect your transformer rappings including the main transformers and any neutral harmonic isolation chokes if you equipment comes with them. they should be honey colored - if they are white they are fried and will need to be replaced.

listen to the fans and make sure they are all working.

finally check and make sure the system is giving no warnings and will run through the complete output on the oneline interface or you could also have a fried logic board.

as another poster says - check the draw on the 3 legs and make sure it is balanced - if not it could indicate many problems,

p.s. if you dont have a full maintenance wraparound bypass on the unit you would be well advised to install one while the unit is out of service. if you ever need to do anything to it in the future when you are loaded - you will hate life if you have to drop your load to service it- ie replace a transformer or such, i have replaced a transformer on a liebert unit - luckily it had a full wrap on it so the load did not have to be dropped.

good luck with them.

[Jay Suds]

Full bypass wrap around is a necessity. Having to drop your load to do maintenance (routine or non-routine) is obviously quite lame.

Battery life will also shorten if you don't have proper cooling in your UPS room. You don't want to skimp on cooling your batteries. They are a real, on-going expense and you don't want to have to incur that expense every 3 years instead of every 5 years because you keep your UPS room at 95 degrees.

On the topic of fans ... we had one go in our Mitsubishi 375kva UPS and it was nearly $3000 to get a new one. Nearly choked on my lunch when I opened that invoice up. Obviously, not a ton of money, but I was just astounded by how much a stupid fan cost.

[WII-Aaron]

Originally Posted by jayglate

You get much better efficiency by going with 2 or 3 smaller units than 1 big unit.

I disagree with you. At full load with an efficiency of 95% it makes no difference weather you have 1 750kVA or 5 150kVA units. Efficiency is the same.

on the low end, while smaller UPS units give you more diversity and resilliance you'll be screwed on efficiency unless you can pull more then 40KW per unit.

A 750kVA Powerware 9315 pulls 44KW minimum and a 160kVA Powerware 9315 pulls 37KW minimum. 37 X 5 is alot more then 44.

I know the thread is about Lieberts but I use the Powerware as examples because the above units are ones I actually own.

Aaron

[RackMy.com]

not hitting them every now and then with a load discharge that will knock the dust of the plates

When you "hit" them with a load discharge you are shortening the length of the batteries. Everytime you go to batts you are decrease it's total capacity.

You get much better efficiency by going with 2 or 3 smaller units than 1 big unit.

One larger unit at full load will be more efficient that several smaller units. That being said, I would never one one UPS in a critical DC environment. It's a single point of failure.