Designing and sizing a standby generator system for a business can be a complex process that requires careful consideration. A well-designed standby generator system can provide reliable power during power outages, emergencies, and scheduled maintenance. On the other hand, designing a generator system that fails to meet the needs of the building can result in added cost, loss, or liability. In this article, we will discuss how to design and size the right standby generator system for a commercial building.
- Determine the Load Requirements and Generator Size
The first step in designing a standby generator system is to determine the emergency load requirements of the building. Load requirements refer to the amount of power needed to keep the building operational during a power outage. The load requirements can be determined by conducting a load analysis, which involves identifying all the electrical equipment and appliances that need to be backed up by the generator and estimating their power consumption.
Sizing the appropriate generator begins with determining if the generator will back up the entire building or just emergency loads. For an entire building, the sizing is often based on peak power demands during summer months, also factoring the amperage size of the electrical service to the building. If the generator will provide standby power for emergency loads only, the emergency circuits will need to be determined, and those circuits will need to be separated from the main electrical panel into a separate emergency panel.
- Determine the Type of Generator
The next step is to determine the type of generator that will meet the emergency load requirements of the building. Most commonly, there are two types of generators to choose from: diesel and natural gas.
Diesel generators include the convenience of an onsite fuel supply. Diesel fuel is also generally available in most areas, making this a popular fuel choice throughout the U.S. Considerations could include a limited run time on the fuel tank which will require refueling for extended power outages. Diesel fuel also has a limited storage life and may require regular maintenance to avoid fuel degradation.
Natural gas generators have the benefit of a long run time from the local utility, as well as lower emissions and lower maintenance costs. This fuel source may not be viable for critical operations facilities, such as healthcare, if onsite fuel storage is required.
Diesel generators are often utilized for buildings with high power demands, while natural gas generators are commonly used for buildings with low to moderate power demands. However, with generator paralleling technologies, multiple generators of either fuel type can be combined to meet a higher power demand, making both fuel types suitable for many large building applications.
- Determine the Location
The location of the generator is another important factor in designing a standby power system. For diesel generators, the location will need to be easily accessible for re-fueling. This often requires a fuel truck to directly fill the fuel tank unless the building is equipped with a fuel storage and pumping system. The location of a natural gas generator will need to be suitable for the utility gas line to be plumbed to the generator with adequate fuel supply and pressure.
The air intake and exhaust should be considered to ensure proper airflow and operation of the engine. The generator location should also be easily accessible for routine maintenance and repair with adequate space around the entire unit.
- Determine the Transfer Switch
The transfer switch is responsible for switching the building’s power source from the grid to the generator during a power outage. The amperage rating of the transfer switch will need to be determined. This can be sized to match the utility service, the main panel, or the emergency panel depending on whether the generator will power the entire building or only emergency loads. When a generator system is sized to run an entire building, the transfer switch may be installed near the utility service entrance to the building, which may require the transfer switch to be service rated.
- Ensure Compliance with Local Codes and Regulations
It is important to ensure that the standby generator system complies with all local codes and regulations. These codes and regulations vary from state to state and can have a significant impact on the design and installation of the system. If you have questions regarding local codes, one of our power experts can consult with you to ensure the generator will be in compliance.
A well-designed standby generator can prevent loss, liability, and life safety risks during a power outage. Proper planning can help ensure the generator system you design will be reliable and meet the needs of both the building and the personnel inside.
For more information about generator system sizing, see Generac’s Power Design Pro™ Generator Sizing Software, or contact your local Clifford Power representative for more information.
Clifford Power Systems, Inc. provides dependable generator equipment, service, and rental. We are solely focused on power generation and offer professional consultation to meet all your project needs. Contact us at any of our locations in Oklahoma, Texas, Missouri, Kansas, or Arkansas.