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Help choosing UPS, and with that "Watt" talking ...

B

b4u

Golden Member
Hi,

I need to by an UPS so to connect a server that runs a database & web server. What I want, is to connect the UPS to the server, so that when power goes down, the server don't go down with it. Instead, I would like to connect the UPS via USB to the server, so that for example when the power of the battery goes down to 10%, the UPS automatically shuts down the server. No more hard power downs, that aren't friendly to databases ... 🙂

So I need some help here ... which one should I buy?

I mean, I don't understand much of that "Watt" talk, so I don't know how many "Watt's" should I look into ...

I want to connect only the server, and if I'm able to, also a switch. People work mainly with laptops, so they have batteries, and if the switch is on, they are able to save their work on the server. But mainly, I want the server conencted.

Looking at this APC's web page, I have some help on chooseing which model fits my needs. For example, for 200W (~320VA), I get the model "Back-UPS CS 350 USB/Serial" that runs for 0:05 minutes.

What are that 200W (~320VA) rubbish? How can I know the Power Draw from a system? The Power Supply box?

0:05 minutes? Isn't it little time?


Thank you.
 
5 minutes is lots of time for you to shut the box down, or have it shutdown 1 minute after the power goes out and the UPS switches on.
 
Well, maybe I'm thinking wrong about that ... I mean, 5 minutes is allot of time for a UPS to shutdown a system, or even 3 minutes if I configure it so that the UPS waits a bit to see if power goes up (like for instance if someone is messing with the electric circuitry without thinking about the computers).

Anyway, what is your oppinion about the times? Of course that a UPS isn't supposed to be a way of working without power, at least in normal work environment ... if I wanted to make sure my server didn't shutdown, I would need a really big UPS sistem and/or power generator ... but that isn't the case.

Do you have any experiences that you can share with me? Or knowledge of a system with such requisites?

Thanks
 
The 5-minute figure is an estimate. How long it lasts depends on what you load it (the UPS) with.
Don't forget that you need to power your monior with it too. Otherwise, when power goes, the monitor will turn off!

The VA figure tells you the maximum current that you can draw from the UPS. The output voltage of the UPS is known. I assume that you are in the US. If that is the case, the voltage is about 120V. The maximum current you can draw from the UPS is the VA figure divided by 110. The unit is Amps [A].

The W figure is the maximum power that the UPS can provide. Power is not the same as Volts multiplied by Amps because of power factor. So, this figure is very important. Look into the manual for your monitor and find out its power consumption. What is the power rating of your PSU in the server? You need to find the power consumption of the switch too. Add these figures. This will be a good estimate (with margin) for the power of the UPS in Watts. The UPS you get should have a power rating (in Watts, not VA) close to this figure.

Neither of these two figures tells you anything about how long the UPS can run before it needs to be turned off. That only has to do with the capacity of the battery (the maximum amount of energy that the battery can store).
But, it just happens that the UPS manufacturers put larger batteries in the UPS boxes with higher VA values.

Most UPS devices let you program them to send an interrupt to the computer when the battery voltage drops below a threshold. That is a sign that the battery is about to run out. You program the computer to turn off when it receives that interrupt.
That APC model you mentioned connects to the PC through a serial port. That's how it sends the interrupt. If you have Win XP, you can program the UPS under control pannel "Power Options".
 
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