UPS Maintenance: Buyer Beware
Mike Elms, sales and marketing director at CENTIEL, outlines what you should look for in a UPS maintenance provider, as well as the importance of batteries when it comes to ensuring the maximum efficiency and availability of your system.
Data centre managers need to protect their critical power with a UPS system which provides power when the main source has anomalies, is interrupted or even fails. It also ensures a high-level of power quality. Therefore, ensuring the highest possible level of availability of a UPS system is of paramount importance. Efficiency is also high on the UPS tick list in order to keep costs under control.
However, it is not just the UPS system itself which will influence levels of reliability and availability. A system needs to be properly maintained to remain efficient, reliable and therefore available.
The most modern modular UPS system will not continue to operate optimally without regular maintenance and support. Choosing a reliable supplier who will act in your best interest as a trusted advisor and give excellent value for money in terms of support is essential.
Key questions to ask when purchasing a UPS are: who will be responsible for maintenance and support? What are the details of the service level agreement (SLA), including guaranteed response time? What is the schedule of preventative maintenance visits? Is there a 24-hour support hotline? It is also necessary to find out if labour, travelling and expenses is included and the cost of replacement parts.
The whole purpose of the UPS solution is to protect the critical load and if there is no valid warranty, proper maintenance and support contract, the whole power source could be compromised however brilliant or cost effective the technological solution. So: who is the warranty held by? Is also an important question. Smaller ‘vendor neutral’ UPS providers source technical solutions from multiple manufacturers. Is the warranty held by them or the manufacturer?
As well as selecting a suitable maintenance and support contract, ensuring that you have the best solution versus your requirements also requires due diligence on behalf of the data centre manager. Cost reduction has always been a big driver and criteria for winning contracts, but if cost-cutting compromises the availability of the UPS then again, the critical load will not be properly protected.
One example I am personally passionate about and see time and time again, relates to batteries. The de-facto standard request of most UPS solutions is a 10-minute run time if the power should fail. At tender or quotation stage the configuration of the battery system can only be determined by calculation. The actual performance of the battery system is only tested once it has been purchased and installed
Battery autonomy calculations have a number of variables which can lead to very different battery configurations which all appear to meet the required specification and run time. These variables include: what efficiency has been used for the UPS unit; the final end of discharge voltage (EODV) value per battery cell and the temperature at which the autonomy has been calculated.
Take temperature for example. Battery blocks will give a better performance (Watts per cell) at a higher temperature, so by calculating the battery run time at 250C will result in the need for fewer batteries.
While legacy UPSs were restricted to a fixed number of battery blocks per string, modern transformerless UPSs can have variable numbers, hence the autonomy calculation can be “fine-tuned”. However, high temperature is a VRLA battery’s enemy. Keeping the battery in a high ambient temperature will impact on its end of life figure.
As battery systems are maintained around the 20-22oC mark then battery calculations should be done at this temperature and the relevant Watts per Cell data sheet from the manufacturer used.
Other points to consider for comparison when it comes to batteries include: what load the battery autonomy has been calculated at: KVA @ 0.8 p.f. or Unity p.f.? Whether there is a separate or common battery system; the number of battery strings, is resilience required; the number of battery blocks per string; 5 or 10 year batteries; battery containment system; method of battery string DC isolation and dimensions of the battery containment system size and weight.
A very simple philosophy that I have is to compare the weight of proposed battery systems when evaluating different proposals. Batteries are heavy so a large difference in weights should flag up a concern. Request information from your supplier about how they calculated their battery run time.
The good news is that UPS technology has improved significantly over the past few years. Transformerless UPS technology has matured and overtaken transformer UPS. Modular UPS offers the newest technology in the UPS evolution and offers real CAPEX and OPEX savings.
Modular technology is now available for large data centres with 100 KVA modules and 500 KVA building blocks. The challenge for any data centre manager is to balance the cost of a UPS system and its resilience. Generally, with UPS solutions, as in life, you get what you pay for, so it is important to study the technical submittals evaluation documentation carefully.
At CENTIEL our design team have been working with data centres for many years at the forefront of technological development. We are the trusted advisors to some of the world’s leading institutions in this field.
For this reason, we have developed our pioneering 4th generation modular UPS system CumulusPower which offers offer industry-leading availability of 99.9999999% (nine, nines), with low total cost of ownership (TCO) through its Maximum Efficiency Management (MEM) and low losses of energy.
Originally featured in Data Centre Review October 2018