Imagine this: During a preventive maintenance (PM) service on the emergency power supply system at a Class A office high-rise, an oil leak was detected behind an intake manifold. A quote to fix the issue was provided, but the approval was delayed. During a run on building load, the unit failed due to an excessive oil leak. The service provider was called out for an emergency repair, which was approved and completed that night, averting a possible catastrophic failure.

Or consider this: While conducting a building load transfer test at a data center, a service provider discovered a switch that would not transfer. A monthly transfer is always recommended, but this customer only performed a quarterly building load transfer. Due to the lack of regular testing, the switch’s contacts were stuck from carbon buildup, requiring the original equipment manufacturer (OEM) to provide new parts for repair.

As Daniel Hornbuckle, Field Service Supervisor for Prime Power Services Inc., notes, both of these service issues are real.

But what would have been the outcome if an outage or weather-related event had occurred? How can a property manager ensure their facility is prepared for a major incident?

To avert such disasters, this article covers key aspects of emergency power supply system (EPSS) maintenance, including exercise frequency, spare parts inventory, testing, qualified service providers, and fuel storage and maintenance.

The Importance of Backup Power in Commercial Real Estate

An EPSS consists of an emergency backup generator, automatic transfer switch and/or switchgear, and electrical distribution, forming a complete system. Proper maintenance is required to keep this equipment compliant and functional. Commercial EPSS applications provide backup to essential and critical loads, such as egress lighting, elevators, servers, uninterrupted power supply (UPS), medical equipment, and HVAC systems—or anything a tenant or building owner deems essential.

If an EPSS supports egress systems (lighting, fire alarms, etc.), it falls into a category regulated by the local fire marshal/authority having jurisdiction (AHJ) as a Level 1 system.

According to NFPA 110, Level 1 systems must be installed where failure of the equipment to perform could result in loss of human life or serious injuries. Thus, NFPA 110 Chapter 8—Routine Maintenance and Operational Testing—specifies strict maintenance and operational criteria for an EPSS.

Key Risks and Challenges of Improper Fuel Storage for Diesel-Fueled EPSS

Underground storage tanks (USTs), above-ground storage tanks (ASTs), and belly tanks (sub-base tanks) require regular maintenance and oversight. Factors such as water contamination or low cetane levels in diesel fuel can cause an EPSS to fail when called into operation.

Understanding Generator Power Needs

Each EPSS is custom-built and designed for its specific site. Engineering design determines the generator size (kW rating), the number of automatic transfer switches, and the configuration of switchgear and electrical distribution. Standby generators provide backup power during outages and are automatically activated, but they are designed for limited operation—up to 100 hours per year under RICE NESHAP regulations.

Generators serve as the primary power source in areas with unreliable grid access and can operate continuously with variable loads. Continuous power generators run at a constant load for unlimited hours, making them commonly used in power plants. Most commercial properties use standby generators, which differ in operation, load handling, and runtime from prime and continuous generators.

Fuel Types and Storage Considerations

Most commercial EPSS units use diesel fuel. While natural gas may seem like a viable alternative, it can be limited by size, application, and local gas utility pressure availability. Additionally, natural gas generators can cause issues with UPS systems or other sensitive equipment due to harmonic fluctuations. Regulatory requirements mandate that underground storage tanks receive annual inspections by an authorized inspector, while above-ground storage tanks and sub-base tanks are also regulated but with fewer stringent requirements. Fuel must be inspected annually per ASTM standards to ensure it remains free of contaminants that could cause generator failure.

Fuel storage tanks are often overlooked, as they are static components with no moving parts. Annual fuel sample tests should be conducted, and monthly checks for water accumulation must be performed. If contamination is detected, fuel polishing and cleaning services can remove water, algae and other impurities. It is critical to maintain an inventory of spare fuel filters, as these can become clogged quickly during extended outages, potentially leading to system failure.

Routine Maintenance and Testing

Annual fuel tank cleaning and polishing are recommended to prevent algae growth and water contamination. It is best practice to maintain fuel levels between 85 and 90%to minimize water buildup while allowing for expansion and contraction. Generators should be exercised weekly for five minutes to bring the engine up to temperature and check voltage and wattage readings.

A monthly 30-minute test on building load, required by NFPA 110 Chapter 8, ensures excess fuel buildup is burned off, reducing the risk of wet stacking. Additionally, every three years, a four-hour building load test at 30%load must be performed. If the building cannot meet the required load, a supplemental load bank should be used.

Improper maintenance can lead to several common issues. Running generators too long without load causes wet stacking, leading to unburnt fuel buildup. Failure to conduct regular transfer switch testing increases the likelihood of switch failure when emergency power is needed. Ignoring service provider recommendations for critical repairs compromises reliability, and battery failures remain the number one cause of generator malfunctions. Ensuring that battery chargers are functioning properly is a simple but essential aspect of maintenance.

Emergency Preparedness and Response

Before a power outage, property managers should ensure emergency service provider contact information is up to date, the fuel tank is adequately filled, and high-mortality spare parts, such as filters, belts, hoses, battery chargers, and block heaters, are stored in a secure location on-site. During an outage, it is important to visually inspect the EPSS for any leaks, unusual odors or excessive smoke. If the outage lasts long enough to warrant preventive maintenance, scheduling a PM service as soon as possible will help prevent long-term damage.

The Consequences of Neglecting Preventive Maintenance

One of the most striking examples of the consequences of improper fuel maintenance occurred during Hurricane Katrina in New Orleans.

In the aftermath of the storm, several hospitals experienced widespread backup generator failures due to contaminated fuel. Water accumulation, microbial growth, and sludge formation rendered many emergency power supply systems inoperable, placing lives at risk and forcing emergency evacuations. The failure of these critical systems underscored the importance of regular fuel testing, conditioning, and securing emergency fuel supply contracts to ensure operational reliability.

Another incident highlighting the risks of inadequate fuel maintenance occurred at a major data center in Chicago.

During an extreme cold spell, diesel fuel thickened due to gelling, preventing proper fuel flow to the backup generators. As a result, the data center suffered significant downtime, leading to financial losses and service disruptions for numerous businesses. This incident demonstrated the necessity of using winter-grade diesel and installing insulated or heated fuel lines to prevent fuel from solidifying in freezing temperatures.

These real-world examples illustrate the severe consequences of neglecting preventive maintenance. By adhering to best practices in fuel management and routine generator testing, commercial property managers can ensure that their emergency power supply systems remain reliable, compliant, and prepared to function during critical moments.

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