Uninterruptible Power Supplies installed in harsh environments

The ideal environment for an Uninterruptible Power Supply (UPS) and it associated battery set, would be in an area that is secure, dust free, dry with an ambient temperature maintained between 20-25C and adequate airflow to meet the manufacturer requirements.

When installing a UPS as part of a new build project or renovation works, the environmental requirements are usually carefully considered and the UPS will be ideally located in order to increase reliability and maximise the operating life.

Sometimes, if the UPS is retrofitted to an existing electrical infrastructure, the ideal environment often isn’t physically available. With poor planning, designers locate the UPS alongside other electrical equipment, such as switchgear located in plant rooms, basements or even outdoor containers. The UPS then may have to contend with the elements of a harsh environment. If this is the case, how can the effects of a poor environment be mitigated?

Dust Filters

In normal operation, the UPS is always running and so a constant flow of air enters and exits the system. If the environment is prone to dust or other airborne particles, the inside of the UPS can become clogged, not only causing cooling problems but coating the internal components with debris and potentially causing failures. Selecting a UPS which features dust filters as standard or which have the option for retrofitting and regular replacement will prevent harmful internal build up of dust compromising the reliability of the system. In extremely poor environments “Conformal Coating” may also be recommended, see below.

Conformal Coating

As already mentioned, the ambient air (and associated airborne particles) are blown through a UPS constantly throughout its service life. Where the air may have moisture present, a chemical contaminant or high humidity content, some manufacturers offer the option to apply a “conformal coating” (sometimes called tropicalisation) to the internal circuit boards. The Conformal Coating is a protective chemical coating applied by the manufacturer before shipping. By being electrically insulating, it maintains long-term surface insulation resistance, thus protecting the electronic assemblies from air-borne contaminants such as salt spray, which will assist in preventing corrosion. This procedure was historically used for “industrial” UPS, but now manufacturers such as Huawei and AEC use this technology as standard on their three phase UPS range.

Summary

Cooling fans degrade over time and have a service life of around five to seven years under good environmental conditions, it is rare a single fan may fail before this time, but if so it should be replaced as soon as possible.

Arranging for a preventative replacement of all the cooling fans at a fixed interval is the most cost effective method by saving on labour expenses and arranging maintenance windows. It is also the best way to increase the reliability of performance of the UPS, reducing the chances of losing the connected load and costly downtime.

Component Failure

With the exception of the battery system, there are two other critical functioning components which have a finite life and are integral to UPS performance, they are the Capacitors and Cooling Fans. Failure of either could cause the loss of connected load, the premature ageing or destruction of other components and result in costly downtime. Here we discuss the reasons why, some frequently asked questions and how to best to avoid this drastic outcome.

Do I know when my fans will fail?

It is possible that before a total failure the fan will start to make audible noise as the grease dissipates and fan bearings start to run dry. Some manufacturers also have tachometers, which will sound an alarm when the fan speed decreases below an acceptable level.

The cooling fans’ service life is affected by the ambient temperature around the UPS, the environment and the load level applied to the output of the UPS.

Preventative Replacement

Most manufacturers recommend a preventative replacement at between five and seven years. Although replacing fans that have not yet failed may seem wasteful, the cost of an individual fan is normally significantly less than the associated labour expense of a UPS engineer along with the time scheduled to take the system offline to complete the replacement. Not only will the preventative replacement of fans be more cost effective than replacing them individually as they fail, it will also minimise the period of time the connected load is at risk while running on mains power while the UPS is in bypass mode. As capacitors typically have the same service lifetime, it can make sense to replace both sets of components together. See capacitors below.

Summary

Cooling fans degrade over time and have a service life of around five to seven years under good environmental conditions, it is rare a single fan may fail before this time, but if so it should be replaced as soon as possible.

Arranging for a preventative replacement of all the cooling fans at a fixed interval is the most cost effective method by saving on labour expenses and arranging maintenance windows. It is also the best way to increase the reliability of performance of the UPS, reducing the chances of losing the connected load and costly downtime.

Capacitors

Capacitors are components inside the UPS that smooth out fluctuations in electrical voltage. A three phase UPS may contain hundreds of capacitors, connected in banks for specific roles. They dampen out any changes filling in the troughs and eliminating the peaks to maintain a constant level. They are used for both DC (Direct Current) and AC (Alternating Current) power circuits within the UPS.

How long will my capacitors last?

Capacitors have an operational lifetime calculated by the manufacturer according to the rated voltage, current and ambient temperature. The lifetime can be optimised by avoiding running the UPS at full load or with a high ambient temperature, but the capacitors are consumable and will fail during the service life of the UPS. Depending on the manufacturer, this is usually between five to seven years. Capacitors should be visually inspected and checked during each service visit.

When should I replace my capacitors?

Waiting for ultimate failure of the capacitors will usually cause damage to surrounding components and possibly cause an interruption to the UPS output, especially if the AC output capacitors fail. Replacing the capacitors as a preventative measure when checks show signs of distress or when recommended by the manufacturer will avoid a UPS failure and potentially costly downtime.

Summary

Prevention is better than the cure. The AC and DC capacitors are of a limited service life which is normally shorter than the service life of the UPS. Regular checks of the capacitors during servicing and replacement when issue arise or when the service life has been reached avoids larger issues caused by capacitor failure. Capacitor failure has been the cause of fire suppression being triggered, damage to other internal components, loss of load and even fire. The preventative replacement of all the capacitors once signs of raging are apparent helps avoid these major issues. As capacitors work together in banks, if one fails it is often more cost effective in site labour and downtime to complete a full replacement.

Why UPS Maintenance?

Uninterruptible Power Supply (UPS) units are often the first line of defence to protect your critical load equipment. They constantly take the incoming mains power complete with spikes and surges and perfectly regulate a clean stable power output.

Careful planning and significant investment goes into UPS as part of a power protection strategy and even business continuity planning. When your UPS is working correctly, you will forget it is there. But should you?

Once a UPS is installed and commissioned it can sometimes be left until it next alarms before giving it a second thought. With UPS becoming a commodity item and initial product price decreasing some manufacturers now start to charge a premium for ongoing service and “maintenance”. But what exactly is entailed in that “maintenance”? That’s why some of the most prevalent questions I have had from users over the years is, what should I include in my UPS service and maintenance agreement? Do I even need one?

The technical stuff

Upon learning the correct switching procedure and safely shutting down the UPS, whilst maintaining critical load through the bypass line, the UPS can then undergo a detailed visual check of all components, connections can be checked and tightened if necessary, signs of corrosion can be noted and excess dust deposits can be removed should the environment be harsh. The DC & AC capacitors, IGBT devices and batteries should be visually inspected for signs of budging, leakage or overheating – all are signs that the components may be failing (or approaching that Bang scenario).

If the visuals check out, the UPS engineer can then restart the UPS and take on-load readings. The DC side of the UPS can be measured for AC ripple of both voltage and current (High ripple on the DC could indicate worn capacitors or aged batteries). The measurement of the output AC waveform can highlight aged AC filter capacitors. Analysing the input power to the UPS can also highlight mains issues such as high harmonics, poor power factor or even just high voltage – for short periods of time the UPS is designed to filter these mains issues from the critical load, but permanent running with higher than nominal input voltage or high harmonic content will cause the premature aging of components within the UPS. If the external factors cannot be rectified, this should be noted and recommended action be taken in due course.

Whilst a user will be able to clearly see any current alarms on the UPS, usually it is only the UPS engineer that is able to download and analyse detailed history logs of conditions the UPS has been subjected to and how it has behaved since installation (or the last service visit). This is all vital information for predicting how long components such as capacitors and batteries will have a useful life for.

Finally, firmware, depending on the age cycle of your UPS it may have a newly updated version of firmware for control of the sophisticated electronics. Only an experienced and trained UPS engineer should attempt this (and if anything doesn’t go to plan, you want him there anyway!). New firmware is vital to prevent you experiencing unexpected events, which unfortunately other users of the same product may have already reported. An upgrade protects you so well worth insisting upon, especially if the manufacturer recommends it.

Sophisticated job tracking

With our sophisticated job management software, we are able to ensure you, the customer gets a timely report as soon as the service has been undertaken. Our engineers have access to your system information, parts schedule and potential likely issues based upon the history of the UPS. This means we are always prepared before we arrive on site and are able to ensure your system is carefully looked after for the duration of it’s life span.

Our findings

Finally, all of the findings during a service visit should be communicated to you in a swift, clear and transparent method. You can then make decisions or ask for assistance or recommendations in actioning.

So, after reading my thoughts on the above, in answer to our questions, what should I include in my UPS service and maintenance agreement? You should ensure that as a minimum all elements discussed above are completed during the visit, then communicated clearly to you along with any potential risks and recommended actions are followed up. Do I even need one? If the UPS engineer is just going to turn up check for green lights then ask you to sign a piece of paper, Id probably just save your money and wait for the Bang.