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What is load bank testing and why is it important?

26th June 2024

What is load bank testing?

A load bank test is used to test the UPS and generator, as an alternative to the building load mitigating the need for intrusive testing onsite.

The main reason for testing with load banks is to prove the UPS and Generator are working at its optimum and to its full capacity, this is rarely achievable with site load.

The load bank test is carried out alongside preventative maintenance necessary to avoid future damages or breakdowns, putting site load at risk. Load bank testing also provides information on a battery’s real life, where the UPS is concerned rather than its theoretical capacity and should be used in combination with impedance testing to determine the overall condition of the battery.

The end users hope that they never have to use their UPS unit – like a fire alarm that exists silently most of the time, in the hope that there will never be a fire. However, it is vital to ensure that UPS and generators are fully operational so they can be called into action if ever needed.

Testing is particularly useful if conducted one week after commissioning a new UPS battery installation, as this ensures that the voltages across the battery blocks have had the opportunity to equalise and the batteries are fully charged. Another useful time for testing is at two-thirds of the UPS battery’s expected useful life, to confirm predicted capacity. If this shows the battery to be healthy, there is no reason to suspect that it will not perform correctly in an emergency, so no further load tests will be necessary.

How is load bank testing carried out?

To carry out the testing process, the load banks should be supplied with suitably rated cables to facilitate effective energy transfer. The load bank should not be placed more than 20 meters from output power distribution unit (PDU) or UPS terminals. Those carrying out the testing should carry out a risk assessment on the site due to the heat produced from the rejected energy that load banks produce from their predominantly resistive elements and fans.

Therefore, allowances should be made for heat dissipation and attenuation of noise during the testing process. Also, the UPS system should not be tested close to an area where people are working, near sensitive alarms or sprinkler systems as a precautionary measure.

Measurements are taken during discharge where the battery and system performances are determined. A load bank test identifies the problems with the generator and the UPS prompting for immediate actions to be taken to facilitate its efficiency.

What are the advantages of load bank testing?

Load bank testing allows any problems or shortfall in capacity to be spotted and rectified immediately, rather than waiting for them to reveal themselves under real critical load conditions.

With the UPS, although valuable as being the only practical way of truly establishing a battery’s capacity and therefore autonomy, the approach has some disadvantages and should be used sparingly. Therefore, it’s important to understand both the full value and the issues that should be considered before setting up a test programme.

Where the generator is tested, the load bank can decoke the engine, ensuring the engine temperature stats and pumps work, and also check the alternator is functioning correctly.

Setting up for load bank testing means disconnecting the real load from the UPS, and making arrangements for its continued supply and protection. It is also necessary to check that the site’s mains supply and power network has sufficient capacity to support the real load and the load bank simultaneously.

Furthermore, completely discharging a VRLA lead-acid battery will mean that for the succeeding short-term it will be incapable of supporting a load fully until it is recharged. Sometimes, batteries can recharge unevenly, with some cells undercharging while others overcharge, leading to possible problems. There are also the practical considerations that load banks can be large and expensive to hire or purchase, and transportation and positioning on site create non-trivial challenges.

It is advisable to carry out regular a load bank test because they will ensure that the components in the power protection system will perform effectively and optimally when needed to support a critical load.

For all enquiries about Load Bank Testing, Generator Maintenance or UPS Maintenance, please do get in touch with our expert team.

[email protected] | 01977 688155