Do You Need A UPS?
It could happen to you at any time, and in a blink of an eye. All it takes is a small spike, surge, brownout, or any other fluctuation in the voltage , and your equipment can be permanently damaged, your data destroyed, and your operating system files corrupted. Faulty electrical power can insidiously wear down your system over a period of time, without you knowing – until – eventually, it fails. One way of avoiding such disaster is to install a UPS. A UPS (Uninterrupted Power Supply) is a power supply that includes a battery to maintain power in the event of a power outage. Most UPS units will also filter and regulate the utility power. A UPS can be used on most electronic equipment, although this article will focus mainly on it’s use with computers.
There are basically three types of UPSs to choose from. Keep in mind that each manufacturer has their own design and changes. The types are as follows:
1. Offline (Standby) UPS
The standby UPS is the simplest and least expensive UPS design. Getting it’s primary power from the AC line (ie. your outlet), this type of UPS switches over to the backup battery automatically when any drop in voltage is detected. When the power is restored, the UPS then switches back. This “no frill” UPS usually has nothing to regulate the electricity although a few manufacturers may include some sort of line filter.
A “ferroresonant standby” UPS is an improvement on the design of the standby UPS. The ferroresonant UPS uses a ferroresonant transformer to switch from line power to battery power. By using this technology there is a source of stored energy that is used during that fraction of a second while the unit switches between line power and battery power. This was once one of the most common UPS designs, and are still made by some manufacturers. Today, most manufacturers have abandoned this design, claiming that it is inefficient, and favor the “online” UPS for models in the range of 1,000 VA or higher.
2. Line-Interactive UPS
Hailed by some to be the most efficient UPS, the line-interactive UPS is one of the most popular designs used today for computer protection. Although some manufactures sell line-interactive UPSs which are no more than an offline UPS with a regulator added, the basic line-interactive UPS has a bi-directional inverter/charger which is always connected to the output of the UPS, and uses a portion of AC power to keep the battery charged. When the input power fails, the transfer switch disconnects AC input and the battery/inverter provides output power. This gives a faster response to a power failure than an offline UPS.
3. Online UPS
This design is considered to be a “true” UPS. Unlike the other types of UPS, this one uses the battery as its main source of power and the line power is the secondary source of power. When line power goes out, the UPS does not have to convert from one power source to another. It just stops charging the battery. This is similar to the way laptops react when they are unplugged from line power. When there isn’t any line power the battery will keep powering the system until its stored power is depleted. Since this type of UPS design runs off the battery, the equipment plugged into it will always maintain a constant flow of power. Any surges or brownouts will be taken in at the battery charger and not passed on to the equipment.
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.
Other helpful tips.
- The battery in a UPS will last roughly 1 to 3 years. It’s a good idea to know where to purchase a new battery before it is needed.
- It can be very useful to have power management software that will automatically shut down an unattended machine in the event of power failure. The power management software is usually provided with the UPS, and often comes in more than one version, to provide compatibility with the various operating systems. Be sure that the UPS you choose has an appropriate communication port (serial, UPS, …etc) and comes with management software that is compatible with your operating system.
- Check the warranty of the UPS. Usually the better quality units have a longer warranty period.
- It’s a good idea to test out your UPS every so often. A good time to do this would be after doing your scheduled backup and maintenance. Turn off the circuit breaker that controls the UPS to simulate a blackout, and see if the UPS does it’s job. Please note that the testing is NOT done by pulling out the plug. Electronic equipment should always have a good ground reference. If you unplug the UPS, it’s still powered but now has what is commonly called by electricians a “floating ground”. Not only is it bad for the electronic device, it can be dangerous too.
- Some UPS units have protection for network and telephone lines. This extra protection can help save your computing and electronic equipment.
- Don’t overload a UPS. It will not work properly when you’ll need it the most, and you will shortening it’s life span.
- When a lighting storm is near, the best way to protect your computers (and other appliances) is to unplug them from the outlets, together with your UPS. A lightning bolt, that can melt holes in steel and jump through kilometers of empty air, isn’t going to even notice the “surge protection” electronics in your UPS and it isn’t going to be stopped by the tiny air gap inside an on/off switch either. So to be on the safe side, unplug everything. Don’t forget to unplug the telephone, cable, and antenna connections too.
- If possible, don’t run your printer, scanner, and other such devices off your UPS unless it is absolutely necessary. These devices will simply add more of a load, causing you to buy a larger and more expensive UPS. Most people really don’t need a battery backup that a UPS provides for such devices, and would be better off buying a good surge protector instead. To learn more about surge protectors see “The Guide to Surge Protectors”.
Jonathan Z. Kremer (better known as Yoni) is the proprietor of “Yoni – Electrical Design and Installations”, a Maale Adumim (Israel) based business that has been serving primarily Jerusalem, Maale Adumim, and surrounding areas since 1989. We undertake various forms of electrical work including renovations, maintenance, installations, and repairs – encompassing the domestic (home), industrial and commercial arenas. We believe that our success tomorrow will be determined by how well we serve you today. http://www.yoni.kremer.co.il