UPS with a back-up UPS

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StreamlineGT

StreamlineGT

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I have a situation where the client wants a UPS and a backup UPS in case of the first one failing. Anybody ever run into this? Can we run them both off the same feeder? Can we load side them both to the same panel without sync problems? Would a static switch work in the case of switching between the two UPS's, instead of swtiching between normal and emergency power?
 
This is a common setup..


Ideally the two UPS are fed from different feeders, one of the UPS's can be the Bypass source or the 2 UPS's can load share. Depends on what they want, bought...
 
Where I work we just had 2 of these installed in parallel, each with a battery expansion cabinet:
http://www.oneac.com/download/files/917201BSinergySEII.pdf

They are fed by 2 seperate feeders and the outputs paralled to feed the critical load panel.
Our design allows one of them to handle the total load in case of failure of the other, under normal circumstances they share the load and their outputs are synced.
 
How to do this best depends on size, a 2MW system will be different to a 2KW

The best approach is to wire your loads (usually computers) to two separate distribution systems, one off each UPS. That way if anything fails on one power chain the equipment is still powered off the other chain. You can't improve on this method in terms of system reliability. This approach relies on all downstream equipment having two or more mains inlets. If you need to power equipment with only one inlet, then a local static switch is what you need.

If you really want two UPSs in a redundant configuration feeding single distribution, and (and this is the really important bit) you want it more reliable than a single UPS, then it gets harder and more expensive. You need a really really reliable static switch, and the only name on your checkbook should be Cyberex. They also make the little local static switches referred to in the preceding paragraph.

Paralleling UPSs can work, but because the two UPSs have to co-operate, they form a union shop, and you can get the case of "one out - all out brothers", so it's an approach I recommend against.
 
Again without a clearer idea of the application it's tough to get specific.

I know that the once you get into the bigger APC systems (2kW+) they offer N+1 redundancy, phase sync, etc. Silcon is good up to 500kW and I think you can get at least 1.5MW with Symmetra MW.
 
It is common for extreme critical loads like data centers. There are two configurations called “Parallel Redundant”, and “Isolated Redundant”.

Parallel Redundant units are not often used in my experience. As the name implies two or more units are installed in parallel and the combined output feed a Static Transfer Switch. The Transfer Switch are fed from the UPS and a Bypass Source

Isolated Redundant UPS are the most common setups and offer the highest reliability as they are wired in the “Exclusive Or” configuration. Minimum system requirement are two UPS units. Both UPS units have Static Bypass Switches installed in them. Unit 1 inputs are Line and a Bypass Source (like a generator or another line). The output of UPS #1 feeds the Bypass Input of UPS # 2. UPS #2 also has line input completing the Exclusive Or operation. The output of UPS #2 feeds the equipment.

I should note either of these two configurations should be designed by professionals like the equipment manufacture overseen by a licensed engineer having experience with such systems. It is not something that should be left to the discretion of an electrician.
 
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What I have seen over the 27 plus years I have worked around UPS is it.

No one design is perfect for every user.
Standards and specifications of the data center customer/customers
Depends on the customer
Nature of how critical the load is to the customer
MONEY and pay back time
Engineers design preference
What the newest product on the market for UPTIME is......and how cutting edge the customer thinks they are
Utilities involvement and availability of dual source utility.

And a few more I can not think of right now
 
dereckbc said:
I should note either of these two configurations should be designed by professionals like the equipment manufacture overseen by a licensed engineer having experience with such systems. It is not something that should be left to the discretion of an electrician.
Click to expand...

I was thinking the same thing from the start of this thread. :)

I consider myself a good electrician that has a fair grasp on this trade. Still...a man must know his limitations. ;)
 
StreamlineGT said:
I have a situation where the client wants a UPS and a backup UPS in case of the first one failing. Anybody ever run into this? Can we run them both off the same feeder? Can we load side them both to the same panel without sync problems? Would a static switch work in the case of switching between the two UPS's, instead of swtiching between normal and emergency power?
Click to expand...

Is your client an engineer? If not then he should state what his desire and expectation is from the electrical system and engineer can provide a solution for it. (Ask him if he goes to the doctor with a headache and tells the doctor that he wants brain surgery?)

The solution requires an engineering reliabilioty study of the system.

Meaning all of it's components from the utility source to the user point. Then several models are developed to find the most reliable power supply.

The weakest part of any UPS sytems is the battery.
 
I did a job once for the Navy where they wanted an entire building backed up with a redundant UPS system. They bought three separate 1 MW units, two of them backed up different sections of the building and the third was a backup in case one of the first two failed. Everything was automatic. If the power went off, #1 and #2 came on; if either of them failed, #3 came on.

Anything is possible, but UPS systems are expensive. The only concern I would have would be the pricetag. The system I mentioned above was about $500,000 for each unit - a total of $1.5 million just for the UPS system.
 
Cost of UPS Systems

Cost of UPS Systems

Having worked for a critical power systems design firm now for about 6 months, I can intelligently chime in on this topic.
Someone mentioned in an earlier reply that no 2 systems are the same. So true. There can be redundancy at any and every level.
The most amazing fact about the business is system cost, on the order of 10-$15 MM per MegaWatt.
A 10 MW greenfield data center would have an expected installed cost of $100-150 MM! .. that's million!!!
Of course that includes mechanical and electrical.

And I don't have a feel for the cost of the equipment protected by the critical power system, but I understand it to be much higher than the cost of the critical power system!

... good market to be in :)

JM
 
brian john said:
So Lazso automatic transfers from UPS to bypass are not important.
Click to expand...

It is Laszlo.

That's not what I said. I said "not really" to your comment that everything happens automatically puts the Uninterruptible into the UPS.

Automatic transfer would not be important as loss of 2-3 cycles that that normal transfer switches take would mean the virtual loss of the critical load. STATIC automatic switching, however, is an essential component in making the power supply uninerrupted, along with many other functions.
 
Laz:
My comment was said lightly normally I use that response, the U in UPS, when someone has a less that adequate battery. But it seemed to fit the moment.

But hopefully all functions supporting the critical load are automatic.
 
ups configurations

ups configurations

streamline, i'm a ups tech and i've been around all sizes and configurations. the big questions that need to be answered are how much load to they have, how much do they plan on expanding, how much room they have and how much money they are willing to spend. PM with the details if you want some help putting it together.
 
ups configurations

ups configurations

streamline, i'm a ups tech and i've seen just about any configuration from all the manufactures. it depends on a few things, how much load they have, how much space they have, if they plan on expanding, and of course how much money they have. Shoot me a PM if you want some help coming up with a one line or suggestions on what brand will best suit your needs.
 
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