ups using in datacenter

litmic used Ask the Experts™
What should I concern when designing & using UPS in servers datacenter?
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Garry GlendownConsulting and Network/Security Specialist

If the DC you're using is unreliable enough that you need to put in a UPS, you're at the wrong DC ...
Apart from that, make sure you have dual power supplies to draw power from two separate circuits, and ensure you're not overloading the circuits (that is, make sure you can operate everything on one circuit in case one feed goes down)
Network Engineer
Is this your datacenter, or a co-location facility? If this is your facility, are you willing to accept some outages due to power failure? If not you are probably better off renting some space in a good co-location facility.

We have our own 24 X 7 X 365 call center and datacenter. We have two diesel generators, either of which can power the building. We run on one generator weekly to be sure that everything is working properly. We have two whole building UPS units. In the datacenter halfof the circuits are on one UPS and half on the circuits are on the other UPS. We buy all the equipment that we can to have two power inputs and make sure that they are connected to separate UPS. Equipment that has a single power supply is attached to an automatic power transfer switch that feeds it's outlets from two separate circuits. I am pretty sure that the whole setup costs over 1 million US dollars.

If you are just trying to ride out some smaller power outages you can possibly get by with just 1 larger UPS. You should still plug everything into two circuits, one of which is one UPS. This way a failure in the UPS doesn't shut down the datacenter. When measuring load on the UPS remember that it could potentially double when utility power is out because everything will be feeding from one power supply instead of two. I would want to keep your load at less than 40%.
Philip ElderTechnical Architect - HA/Compute/Storage

The Data Centre will have its own power systems with UPS systems providing backup power to allow the Automatic Transfer Switch (ATS) time to flip between incoming A/C from outside and internal generator in the event A/C goes offline.

One cannot plug a UPS into a circuit already protected by a UPS setup (looping).

One can provide their own ATS for single power source items such as switches, routers, and such but that is about it.

Equipment being utilized in the DC should have dual Power Supplies if at all possible to take advantage of the A/B power channels to be found in the enclosures (usually two external power sources for high end DCs).
Top Expert 2014

Why don't you ask litmic to qualify what they mean by datacenter? Chances is it's a server room in their office.


Bets to discuss this with your datacentre providers as you need to check the systems they provide before adding your own UPSs for the following reasons:

1) it may be pointless.
if they have resilient systems in place you may not need a UPS, particularly if your contract includes guaranteed uptime and compensation for loss of power.

2) they may be able to provide multiple power supplies for you.
many datacentres have multi phase power systems so you can connect any device with multiple power supply inputs to completely independent supplies from the datacentre

3) the UPS may not like their systems
a UPS monitors the power input and assesses the quality. due to the way UPSs work, the electricity output they provide while running on battery is not the same as the power provided by the power company and can trigger many UPSs to assume the power is effectively down (even though it is still being supplied by the DCs UPSs) this negates the whole point of using 2 UPSs so may not be worth it

4) the overhead of the UPS
using a UPS adds a small amount of power drain to the load, as the UPS needs to power itself and keep its battery charged. daisy chaining UPSs usually works as long as the 2nd UPS is significantly lower capacity than the 1st one it is connected to. if not you may find the 2nd UPS draws too much power fro the 1st and effectively causes an overload when the 1st UPS flips to battery.

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