How to Set Up a Reliable Standby Power System

A standby power system isn’t worth much if you can’t count on it to deliver when needed. Here are some ideas for setting up a system that’s always ready to run reliably.
How to Set Up a Reliable Standby Power System
All-weather enclosures help ensure reliable emergency generator performance. Enclosures can also be sound-attenuated to limit the effects of noise on neighboring properties.

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A reliable standby power system is vital to any water or wastewater treatment plant. Without one, a storm or other event can knock the facility offline and put the drinking water supply or local water resources at risk.  

Just having a generator on site is not enough — it needs to be sized to fit the facility’s needs, installed properly and maintained effectively. Managers, supervisors, operators and technicians share responsibility for ensuring reliable emergency power. When installing a new generator or upgrading an existing one, three components are especially important:

  • Meeting the National Electrical Code (NEC)
  • Identifying the proper motor starter
  • Integrating the generator with the entire plant operating system

Meeting code

Ask your consulting engineer to confirm the type of emergency power system your plant needs. The requirements are dictated by the NEC. The required generator size varies with specifics of the operation and the amount of equipment that needs to run at any given time.

An accurate load schedule and sequence of operations is critical to proper generator sizing. A sizing tool can help in verifying different sizing approaches. When choosing a generator, make sure it is sized for a full load, meaning it has capacity to power all equipment in the facility at one time. It’s rare that all components (pumps, blowers, dryers and more) will operate at the same time, but it’s important to be prepared in case that should occur.

A treatment plant can choose a generator with less capacity than the plant’s full load if certain equipment or processes can be taken offline or cycled.
Various other code requirements must be considered. These include a 60-second startup time and on-site signage indicating the generator type and location — this is vital if first responders need to locate the generator and obtain operating data.

Additional considerations were added after poor generator performance during relatively recent natural disasters, such as hurricanes. These codes aim to ensure that standby power systems can support mission-critical operations for extended periods. Here are five actions your consulting engineer should consider:

  • Perform a risk assessment.
  • Ensure full-load, 72-hour continuous alternate power sources by having ample diesel fuel storage on site, and consider dual fuel standby.
  • Review all sources and circuits for grounding compliance.
  • Protect against damage, such as flood-proofing (installing generators in a high location) or selecting a wind-rated, aluminum-coated enclosure to protect against saltwater damage.
  • Understand special requirements. Consult your authority having jurisdiction for local or state requirements.

Motor-starting capabilities

The vast majority of treatment plant components are driven by motors, and that makes it important to choose the appropriate motor starter for a generator. There are three basic motor starters: across-the-line starter, variable-frequency drive (VFD) and reduced-voltage drive.

VFDs require the least power to start the generator and allow sustained operation at varying operating speeds, making this a user-friendly option. VFDs can also help lower energy consumption and costs. VFDs can reduce energy usage by as much as 70 percent while extending equipment life.

An across-the-line starter, the simplest and least expensive option, quickly applies full voltage to the motor. However, reaching full voltage that quickly increases torque, creating mechanical stress that could reduce generator service life. It also stresses the power supply, leading to voltage dips that may impair equipment operability.

Reduced-voltage starting is designed mainly to avoid the large mechanical pulses that go with starting a motor. It is older technology, largely replaced by soft starters, which offer a greater range of torque at a more attractive price. Reduced voltage still has a place as it tends to work best with high-horsepower motors occasionally found in water and wastewater facilities.

There are numerous reduced-voltage starters, each with its own advantages and ideal fits:

  • Autotransformer or solid-state starters work well with medium-voltage motors. Autotransformer starters also fit well with motors larger than 200 hp.
  • Primary-impedance motors are suitable for lower-horsepower motors.
  • Part-winding or wye-delta starters require motors with special windings, which means a more intricate, expensive and involved design.

Soft-starter technology entails an electronic, reduced-voltage motor starter. It can ramp up voltage to the generator, creating a softer loading that helps limit voltage and frequency dips.

Controller integration

Water and wastewater treatment plants contain many types of machinery, all incorporated into one building management system. A standby generator must integrate with this machinery. Choosing the right controller helps ensure that all components work together.

Controllers are standard on most generators, but each controller offers various options that can affect operations. For example, a traditional controller configuration may have separate controllers for individual functions. More modern controllers integrate all functions into one hardened controller.

A controller interface may also have varied capabilities. A traditional configuration may have a limited display with a reliance on fault code numbers. Newer models offer a more comprehensive display with touch-screen monitors and diagnostic screens.

Controllers also offer different levels of data logging and trend identification. Older models log outage events and alarms together, which can result in normal events displacing alarms. They are also limited in their ability to identify outage trends. Modern controllers boast high-speed data capture with time-stamped event and alarm logs that enable them to fully track any trends in plant power.

Predictive maintenance, a newer function in controllers, can significantly enhance generator reliability. With predictive maintenance, team members can monitor filters, batteries, belts and other components and estimate their remaining life so that they can be serviced or replaced at the optimum times.

A word about maintenance

No one factor determines the right emergency power system for a given treatment plant. It’s important to consider all factors when sizing, installing and configuring the generator that will best keep the plant up and running when utility power fails.

One constant, though, is maintenance. Many generators come with an engine maintenance schedule supplied by the manufacturer. It’s important to have a preventive maintenance plan in place. Routine engine exercising and maintenance helps keep your generator operating safely and properly over a long period of time, preventing downtime at your plant.

About the author

Mark Sweeney is a power solutions manager at Generac Power Systems, a supplier of generator sets for multiple purposes, based in Waukesha, Wisconsin. He can be reached at


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