This help guide is a beginners guide to help select an appropriate Uninterruptible Power Supply. If in doubt, contact us and we can guide you through your choices.

This guide is primarily focussed on single phase systems, that is, systems that can be plugged into your standard UK socket. Links to other resources are at the bottom of this guide for more complex Uninterruptible Power Supply discussions and for specialist applications.

Contents

• Which Uninterruptible Power Supply is right for me?
• UPS Rating
• Links to Other Useful Information

There are three main types of Uninterruptible Power Supply technologies:

• Offline or Standby Types
  • Choose this type for basic power protection for a non-essential PC to allow you to ride through short power interruptions or shut down your system safely.
  • All Offline or Standby UPS Systems have a square wave inverter
  • Standby types are small, quiet and unobtrusive.
• Line Interactive
  • Line Interactive UPS Systems have some voltage regulation providing a simple boost or buck to the incoming power. This prevents them from going to battery too often. If you suffer from mains dips or brown outs a line interactive type has benefits over the standby types.
  • Another factor is the inverter. Some line interactive UPS Systems have square wave inverters, and others have sine wave inverters. The difference is obvious in the price. Square Wave Systems are now just as economical as an offline system, although they are a little bigger and heavier. They should be used in the same way as an offline UPS
  • Sine wave systems are an excellent choice for mid range applications. They are quiet in operation and provide high levels of power protection, due to the fact that enhanced filtering and surge suppression is normally standard for these higher end systems. These systems are fine to use on a wide variety of applications although at high power levels they start to become rather heavy and bulky. Usually so much so that the higher powered versions require 2 boxes - one for the UPS and the other for batteries.
• Online Double Conversion
  • An Online Double Conversion UPS System is always on, effectively isolating the input from the output. Your load is provided with clean power all the time making online double conversion technology the preferred technology for critical systems.
  • They are generally more expensive than other technologies, although the differential is now small. Due to the forced cooling required, the fan noise can be a distraction and hence this technology is not recommended for quiet environments. These UPS Systems can usually be provided with extended run battery banks to enable hours of runtime if required.
  • Online Double Conversion UPS Systems provide the highest degrees of power protection

Here, at Power Inspired, we believe in providing the highest value products. Consider the following Cost-Performance Chart:

The leading brands can, and do, charge more for their products, hence the value of these products is reduced as you can buy technically equivalent products at lower costs, making these products higher value. The VIX Series UPS represents a low cost UPS at the low end of the performance spectrum, but represents good value as the cost paid for the relative performance is low. The KR Series on the other hand represents great value as the cost is low, and the performance is high. You can opt for online double conversion technology at similar prices to the line interactive PS Series UPS.

Of course, performance is relative. You may need a very small and discrete UPS which makes the VS Series of better performance than the slightly larger VIX Series.

The DS Series is more expensive than the KR series, but has enhanced features that ultimately you will need to pay for. If you don't require these features, choose the KR Series series instead.

Although we always recommend online double conversion for the best power protection, it is not always appropriate to do so. In environments where fan noise would be a distraction, or efficiency is a concern, then a sinewave line interactive UPS such as the PS Series provides a great alternative.

Every Uninterruptible Power Supply is rated primarily in Volt-Amperes, or VA. This value indicates how much power the Uninterruptible Power Supply can deliver. Similar to the fact that you cannot put a 3Amp fuse into the plug of a piece of equipment that draws 10Amps you cannot draw 1000VA from a UPS System rated at 500VA. Each piece of electrical equipment that operates at mains power voltages must, by law, have a rating plate. On this rating plate you will see how much power your equipment uses. In some instances this will be displayed in Amps, in other times, Watts and occasionally VA.

If the rating is in Amps, multiply this figure by 230 and you will get your VA Rating.

There is another factor that needs to be considered. Every Uninterruptible Power Supply has not only an obvious VA rating, but also a Watts rating which is usually less than the VA rating.

In order for your Uninterruptible Power Supply to work correctly, you must not exceed either the Watts rating, or the VA rating. Most Uninterruptible Power Supplies have a Watts rating of 0.7 times the VA rating. For example a 1000VA UPS has a Watts rating of 700W. So, how can you be sure you have selected the correct UPS?

Well, the easiest way to be sure is to work out your loads VA rating and multiply this by 1.4. If Watts or VA are quoted on the rating plate then multiply these by 1.4 also. If you purchase an Uninterruptible Power Supply rated higher than this figure you will have no problems.

In order to help you, we have put together this Power By Device tool which has all the factors taken care of. Just select the devices you want the Uninterruptible Power Supply to support, and the tool will determine your power consumption.

Then you can select the Uninterruptible Power Supply that is rated above this figure.

• The Power Protection Blog contains a host of useful and informative articles on UPS Systems.
• This UPS Demonstration aims to show you how the different technologies of UPS function