Knowledge Hub

Keeping you updated

CPD Seminars

Facilitated by backup power and battery experts we offer free CPD seminars targeted at consultants and electrical engineers.


Answers to the most common questions we get asked. For more detailed information and for tailored advice please contact us.

CPD Seminars

Keeping your teams up to date

Continu are regarded as industry experts in backup power and energy storage based on years of working as specialist engineers, ongoing international training and sound technical competence. We are passionate about sharing our knowledge with interested Mechanical & Engineering and IT consultants by delivering monthly CPD CIBSE accredited workshops. To organise one for your team, please contact us.

Topics include (tailored to your needs):

✔ Basics of Power Protection

✔ Power Quality Problems

✔ UPS Fundamentals

✔ Various Types of UPS

✔ UPS Architecture

✔ Latest UPS Technology


The most common questions we get asked


This section is intended to provide answers to the most common questions we get asked. For more detailed information and for tailored advice please contact us


What is a UPS?

The general perception is that a UPS is just for emergency power, in the event of a power failure. However a UPS has two main functions and the second function is arguably more important. In fact approx. 80% of electrical problems are due to in-building phenomena, e.g. Lifts, air conditioners, copiers, florescent lighting etc.

Uninterruptible Power Supply (UPS) is installed between critical loads and mains supply. Utility companies, are not committed to provide clean, uninterrupted power to sensitive IT equipment. An interface is required, there are two functions:

  • To provide short term emergency power in the event of a complete mains power failure and
  • To protect the load from power quality problems, including spikes, voltage dips, fluctuations thus providing a clean and stable supply to protect sensitive I.T. equipment.

Why should I invest in a UPS system?

UPS Return on Investment is very quick. Downtime is very expensive and rising in our ever growing digital world. What would the cost of downtime be for you? Consider the loss of business or potential business, not to mention loss of customer confidence? Consider these statistics:

15% of British companies having suffered a computer crash lost £1 million. 20% lost from £250 000 to £1million. Over 33% lost between £10 000 and £250 000.

It typically takes 4 hours to get a system up and running again after a crash. A recent survey of 450 leading companies showed that each organization suffered, on average, 9 computer failures a year.

What are the different types of Power quality problems?

Our technological world has become deeply dependent upon the continuous availability of electrical power. The national grid is responsible for supplying consistent and reliable transmission of electricity to our homes and businesses. Everyone is aware of the problems associated with Power failures however there are other power quality problems that can be as dangerous to critical loads as a partial or complete mains power supply failure leading to damage to sensitive electronic equipment. Understanding these types of Power problems, their magnitude and frequency will affect the choice of power protection selected.

Sags are short duration voltage reductions below the nominal mains power supply, typically lasting for several cycles. Sags are one of the more common forms of disturbance caused by starting large loads (such as starting up a large air conditioning unit) or large motors inside a production facility. This can cause component stress, heat build-up, data corruption and errors in production processes.

Brownouts are the result of long-term problems that create sags. The term ‘brownout’ has been superseded by the term ‘undervoltage’ Undervoltages can create overheating in motors, and can lead to the failure of non-linear loads such as computer power supplies. The solution for sags also applies to undervoltages.

However, a UPS with the ability to adjust voltage using an inverter first before using battery power will prevent the need to replace UPS batteries as often. More importantly, if an undervoltage remains constant, it may be a sign of a serious equipment fault, configuration problem, or that the utility supply needs to be addressed.

Surges are a short duration of very high voltage increases. Surges can be caused by electrical storms and the same causes as for sags. The result can be data errors, flickering of lights, degradation of electrical contacts, semiconductor damage in electronics, and insulation degradation. Power line conditioners, UPS systems, and ferroresonant “control” transformers are common solutions.

Spikes and Transients
The impulsive transient is what most people are referring to when they say they have experienced a surge or a spike (lasting only a few milliseconds) many different terms, such as bump, glitch, power surge, and spike have been used to describe impulsive transients.

Causes of impulsive transients include lightning, poor grounding, the switching of inductive loads, utility fault clearing, Electrostatic Discharge (ESD), florescent lights, lifts, fridges and freezers. The results can range from the loss (or corruption) of data, to physical damage of equipment, for example, motherboard and processor damage, memory loss and data corruption. Of these causes, lightning is probably the most damaging. Two of the most viable protection methods when it comes to impulsive transients pertain to the elimination of potential ESD, and the use of surge suppression devices (popularly referred to as transient voltage surge suppressors: TVSS, or surge protective device: SPD).

Electrical Noise
Electrical noise is unwanted voltage or current superimposed on the power system voltage or current waveform. Noise can be generated by power electronic devices, control circuits, arc welders, switching power supplies, radio transmitters and so on. Poorly grounded sites make the system more susceptible to noise. Noise can cause technical equipment problems such as data errors, equipment malfunction, long-term component failure, hard disk failure, and distorted video displays.

Harmonic distortion is the corruption of the fundamental sine wave at frequencies that are multiples of the fundamental. Symptoms of harmonic problems include overheated transformers, neutral conductors, and other electrical distribution equipment, as well as the tripping of circuit breakers and loss of synchronization on timing circuits that are dependent upon a clean sine wave trigger at the zero crossover point. Solutions to achieve the lowest possible levels of harmonic distortion can be achieved by installing a UPS system.

Frequency Variations
Frequency variation is extremely rare in stable utility power systems, especially systems interconnected via a power grid. Where sites have dedicated standby generators or poor power infrastructure, frequency variation is more common especially if the generator is heavily loaded. IT equipment is frequency tolerant, and generally not affected by minor shifts in local generator frequency. What would be affected would be any motor device or sensitive device that relies on steady regular cycling of power over time. Frequency variations may cause a motor to run faster or slower to match the frequency of the input power. This would cause the motor to run inefficiently and/or lead to added heat and degradation of the motor through increased motor speed and/or additional current draw.

A blackout or interruption is a complete mains supply failure. This can last from a millisecond to several hours. The causes of interruptions can vary, but are usually the result of some type of electrical supply grid damage, such as lightning strikes, animals, trees, vehicle accidents, destructive weather (high winds, heavy snow or ice on lines, etc.), equipment failure, or a basic circuit breaker tripping. While the utility infrastructure is designed to automatically compensate for many of these problems, it is not infallible. An interruption, can cause disruption, damage, and downtime. The most common mitigating devices employed are the uninterruptible power supply (UPS), motor generator, and the use of system design techniques that take advantage of redundant systems and energy storage. When the power goes out, these forms of alternative power can take over. For more information on types of Power Problems see – White paper 18

What type of Load do you have?

Critical Loads – These are systems that directly affect the ability of an organisation to operate and must be kept operational as far as possible and will not withstand a power break of more than a few milliseconds. For these systems a UPS and generator will be required.

Sensitive loads – These are systems that require a ‘clean’ and controlled shutdown. They cannot withstand power fluctuations or any delays in starting up the generator. A UPS is required to provide the power to the equipment whilst it shuts down correctly, preventing system crashes, data loss/corruption and hardware damage.
Essential loads- These are systems that must be supplied with power in the event of power failure, but can withstand a short power interruption before the generator starts, for example, general lighting.

What is the difference between a generator and a UPS?

A UPS system is used to ‘bridge the gap’ whilst a standby generator is started and synchronised. A UPS is essential to protect critical and sensitive systems which cannot be allowed to fail or require a ‘clean’ shutdown and cannot withstand power fluctuations whilst the generator starts up.

What are the different types of UPS?

There are three types of static UPS available, known as on-line, line interactive and off-line.

An on-line UPS also known as double conversion system because of its two voltage conversion stages: rectifier (AC to DC) and inverter (DC to AC). The purpose of an On-Line UPS is to supply a clean, stable and regulated electrical supply, allowing frequency variations to be maintained within prescribed limits. This type of UPS offers protection for individual servers to large data centres or large production sites.

Line Interactive
Line Interactive is the most common design used for small business, Web, and departmental servers. In this design, the battery-to-AC power converter (inverter) is always connected to the output of the UPS. Operating the inverter in reverse during times when the input AC power is normal provides battery charging. When the input power fails, the transfer switch opens and the power flows from the battery to the UPS output. With the inverter always on and connected to the output, this design provides additional filtering and yields reduced switching transients when compared with the standby UPS topology.

This UPS is the most common type used for desktop computers. The transfer switch is set to choose the filtered AC input as the primary power source, and switches to the battery / inverter as the backup source should the primary source fail. When that happens, the transfer switch must operate to switch the load over to the battery / inverter backup power source. The inverter only starts when the power fails, hence the name ‘off line’ High efficiency, small size, and low cost are the main benefits of this design. With proper filter and surge circuitry, these systems can also provide adequate noise filtration and surge suppression. 

What Electrical Phase do I need?

There are various aspects which affect the choice of unit. Single phase is typically for units under 20kVA. Above this size it is usually necessary to use three phase for both input and output. 

I have a mission critical facility - How do I avoid disasters?

A disaster preparedness plan is crucial to organizations operating in 24/7/365 environments. The goal is zero disruption therefore management must carefully evaluate and mitigate risks to the physical infrastructure that supports the mission-critical facility. While business continuity planning typically addresses Information Technology, this paper reviews and discusses the requirements of the facility’s infrastructure as part of a comprehensive business continuity disaster plan. Without a proper disaster mitigation plan for the facility’s infrastructure, the overall business continuity plan is built on a risky foundation. If a natural, human, or technological disaster strikes your facility, are you and your infrastructure prepared? Does your organization have procedures in place to prepare for severe winter storms, earthquakes, tornados, hurricanes, or other disasters? Surviving tomorrow’s disaster requires planning today.

How long will the UPS batteries last?

Batteries have a design life and this will almost certainly differ from the lifespan of your UPS system. There will be a standard design life, however this will depend on a number of factors including:

Charge/discharge cycles – constant discharging of batteries will cause them to reach their end of life prematurely.

Temperature – the optimum temperature range for a VRLA battery is 20-25ºC. Higher ambient temperatures may improve performance but rapidly age the battery. The batteries themselves also generate heat. It is therefore important to consider the cooling system should maintain optimum battery temperatures.
Your batteries should be checked on a regular basis to ensure your UPS will function correctly.

Why do I need to maintain the UPS batteries?

Unfortunately batteries are consumable items of your UPS system and they do fail. In our experience a large percentage of UPS problems are due to avoidable battery issues. Protecting your system from expensive downtime is achievable and since a sizable percentage (approx. 80%) of UPS failures are caused by batteries, it’s imperative to maintain the batteries. 

How do I optimise the lifespan of the UPS batteries?

To ensure you optimise the battery set performance over the longest possible working life, there are two main solutions:

Battery Testing – to understand the ‘health’ of individual battery cells it is imperative to carry out an impedance test. Our engineers are fully trained and have specialist meters and software to test and identify any faulty cells, all with minimum disruption to the operation of the UPS. The engineers will provide a detailed report of your batteries.

Battery Monitoring – this is a permanently fixed solution that consists of a monitoring device connected to each battery block and string. Critical services such as Data centers, financial services, heavy industry, communications and transport deploy battery monitoring systems for that added peace of mind. Continu offer PowerShield Battery Monitoring system. The modular structure of the PowerShield solution enables you to monitor all of your installed batteries, it may be a single battery string, a multi system site or all of your sites around the world. 

Why do I need a UPS Service Support Plan?

In order to ensure your backup power will actually work in the event of a power failure and that it is operating correctly, (remember, it has two main functions to protect the load from power quality problems as well as power failures), then it needs regular service to identify and prevent potential problems before they occur. Continu offer various Service Support Plans to suit your organisation. 99% of our customers take the view that a Service Support Plan is integral to the ownership of the UPS.

What if our UPS system is still under warranty?

Although your UPS unit may still be covered by the manufacturer’s warranty, most businesses benefit from having a Service Support Plan in place. This is because the manufacturer’s warranty will not guarantee engineer response times or cover preventative maintenance.

What should I do, we are relocating?

So, you’re relocating, and only realised just how heavy that UPS was when you tried to pick it up. You also need to make sure your systems are kept up and running whilst disconnecting exisiting telcoms/utilities etc. Your backup system is critical at this time so ensure your office move planners have covered this. Have you checked the batteries on your UPS? Is the UPS the correct size for the new location? Our team can help you with your planning. Our skilled team of engineers will disconnect your UPS, take it to your new site, put it where it needs to go and re-commission it. We can even do it out of office hours for a seamless relocation.

We need to get rid of our old UPS, what should we do?

Your UPS may have been upgraded and your old one is now obsolete. Bear in mind it is illegal to dispose of units without the necessary compliance due to environmental constraints covering the disposal of batteries and printed circuit boards. We have the necessary credentials to safely remove and dispose obsolete UPS units and batteries in line with the current EEC regulations and will provide you with the necessary documentation.

“Excellent leadership and commitment demonstrated during the audit with a comprehensive knowledge of the concepts of HSEQ Management, the requirements of the applied standards and specific application to the company’s operational needs. There is an excellent integration of HSQE management and a real appreciation of the link between IMS performance and business performance. Excellent oversight of the processes with an emphasis on continual improvement. The Directors have been very successful in communicating HSEQ policy, objectives and targets. An Excellent HSQE culture has emerged as a result.”

IMS External Auditor – Audit Summary