In today's era where mission-critical infrastructures rely on emergency power systems to act as a backup during power outages, it is imperative that your electrical equipment, such as generator sets (genset) and UPS systems, can operate outside of the network and start up perfectly. If power failure is not mitigated, it could have a huge impact on the world's interconnected businesses – from operational disruptions to the inevitable loss of profits.
Take as an example the large-scale power grid that supplies electricity to all end users in residential, commercial, institutional or industrial applications. Despite the small scale of the affected area, sudden or planned power failure can be transferred in a cascade effect, causing repercussions in almost all sectors.
Airport terminals with dysfunctional emergency power systems are major sources of canceled flights and stranded passengers, disrupting businesses that could make full use of available labor and equipment. In the event of a power outage, hospitals also depend on a backup power system to preserve vaccines and support patients' lives with mechanical ventilators. As a preventive measure in life or death situations, it is very important that these electrical design criteria are addressed early in the planning phase.
Given that you have your emergency generator systems installed to run when the power goes out, the question here lies: are they running at full speed? And if so, are they operating at maximum capacity? This is when and why you should perform a load bank test to assess whether your generator set will operate at optimal performance. The regularity of load bank testing – annual, semi-annual, quarterly or monthly – will depend on code requirements, load application, size, capacity, nameplate rating and type of the generator set itself.
Test the functionality of your generator through load banks.
What is Generator Load Bank Testing?
Generator load bank testing is an important aspect of preventative maintenance – requiring a thorough assessment and examination of your generator components under load conditions. When there are no recurring power outages in your area, your backup and emergency power systems only run with little or no load for a long period of time. However, this is not enough as there is no guarantee that your generator will reach its full performance capacity when a power failure occurs. Generators become insensitive over time – and in the worst case scenario, if not maintained – can cause fire and safety risks, high operating costs and increased emissions.
Observe generator load bank testing as insurance for contingency options during emergency power situations. Despite constant exposure to light loads, your generator will need periodic testing to ensure it meets some of the most stringent electrical codes. To eradicate unnecessary downtime and ensure the continuity of electricity flow, your generator should undergo load bank testing.
In fact, NFPA 110: Standby and Emergency Power Systems mandates that after initial installation, acceptance testing be performed. In accordance with 7.13.4.3, your backup and emergency power systems must be tested at full load for two hours on site at their initial commissioning. In addition to these initial acceptance tests, monthly load bank tests are required in accordance with 8.4.1 of NFPA 110. Mission critical infrastructures require additional proactive and preventative measures by subjecting generators to quarterly, semi-annual, and annual load bank tests. .
Here's the general rule of thumb: When your generator has no exposure to more than 30% of its rated kW load, that's when you need to consider load bank testing. According to the specific clause of NFPA 110 8.4.2, generators must be imposed a minimum load of 30% of the nameplate kW rating or as recommended by the manufacturer for exhaust temperature. Otherwise, neglecting scheduled maintenance or operating the generator with zero to light loads can have undesirable repercussions.
Wet stacking
Case in point, diesel generators not subject to the minimum 30% kW rating are susceptible to wet stacking. Operated only at light load or zero frequency, diesel generators over time accumulate carbon deposits on their specific components such as injectors, exhaust valves and exhaust system – leading to unburned fuel, dirt build-up, oil leakage and black combustion gases.
To correct this condition and burn off carbon deposits, prepare the diesel generator for load bank testing and run the engine for a few hours at 30-40% of rated load per NFPA 110 8.4.2. Operating the diesel generator at full power will recalibrate it back to its rated operating temperature and pressure level, clearly serving the purpose of why load bank tests should be performed regularly.
How Generator Load Bank Testing Works
Routine exercise of your electrical equipment is mandatory for its proper maintenance and efficient operational status. To test whether your generator is in proper operating condition, operate it under artificial loads at its maximum operating capacity for an extended period of time.
Load banks test your generator at its total kW output rating in incremental steps to see if it can produce the higher power required when connected to the generator's AC output. This load step switching can be calibrated via a control panel to appropriately match the rated capacity of the generator. Each time you place an additional kW load, critical data such as engine parameters (proper operating temperature and pressure level) are simultaneously recorded to evaluate the efficiency of your generator. In addition to load bank testing, you can also use infrared scanning as a preventative measure for early problem detection.
Specifying load banks involves taking into account the physical configuration and installation considerations. Load banks can range from permanent to temporary, covering a full range of uses – unit-mounted, radiator-mounted or portable. When installing load banks, location is the main issue to consider. For permanent installation of load banks, minimum physical separation between the load banks, the building, and landscaping is required for adequate cooling airflow and damage control. The same principles of proper site location also apply to portable load bank junction boxes.
Conclusion
As the demand for a reliable emergency power system increases, so does the generator load bank. Investing in periodic load bank testing for your generator ensures you experience a multitude of benefits, including backup capability, proactive problem detection, optimal cooling system performance, and elimination of wet stacking. Our expert electrical engineers will guide you through the design specifications so you can take full advantage of generator load bank testing.
