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Do You Need A UPS? (Page 4)What size UPS do I need? The power requirements of your equipment will determine the size of UPS you will need. You can check how much power your equipment uses by reading the plate on the back of each device. UPS units are rated in VA (Volt-Ampere) which you will probably not find anywhere on your equipment. Calculating the VA of an appliance is relatively easy though. If you are given the current that the device uses in amperes (A), then simply multiply the amperes by the line voltage (220V in Israel) to get the VA. For example, if your appliance uses 2A, then multiply 2 by 220 (or whatever the voltage is in your area) and you will get 440VA. If you are given the power in watts (W), simply divide the watts by the power factor (0.7 is generally used if you don't have the equipment to measure). For example, if your device uses 320W, then divide 320 by 0.7. This will give you 457VA. Therefore the first step would be to add up the VA of all the devices that you will be running off the UPS. The next step would be to add 25% to the above sum. It is highly recommended that a UPS has a capacity that is at least 25% greater than the total power capacity requirements of the connected equipment. So as a sweeping example of all that has been mentioned above, let's say you have a computer that uses 200W and a monitor that uses 320W that you want to run off a UPS. You would first have to add them together for a total of 520, and divide 520 by 0.7. This will give you a total of 743VA. Then add 25%, which gives you a grand total of 929VA. Your best bet would be to buy a 950VA or 1000VA UPS. Keep in mind that all the above calculations are for single phase UPS units only. Depending on whether you are protecting many computers, or just one or two, you may decide to connect all the computers to one central UPS instead of using individual UPS units for each station. This may be more cost effective. A UPS is not generally intended to be an alternative power supply. They are used to protect your systems by warning you of a power problem, and give you time to close down your applications and computers before the inevitable happens. Therefore, most UPS units are designed to provide about ten minutes of backup power (with small differences between manufacturers). This is usually enough time to back up what you need and appropriately shut down the connected equipment. It is advisable to look over the specifications of the UPS you are considering to buy. If you need more backup time, then you must buy a larger UPS. It must be noted that buying a larger UPS does not always give you more backup time. The size and type of battery used in the UPS has a lot to do with it. UPS batteries are rated in Ah (ampere-hours). Ah represents the amount of energy a battery can hold. This measurement helps determine how long the battery will power the equipment it is used in. The more 'Ah' the longer the run time. |
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