How to Choose a Generator for an Industrial Facility

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The Right Generator for an Industrial Facility

The selection of a generator for an industrial manufacturing facility is not as simple as choosing a backup generator for a home, office building, or local retail establishment. Using the existing electrical system in a previously occupied building might seem like an easy choice. If the operation is very similar, it might make sense. Otherwise, it isn’t quite that simple.

Determining Factors for Size and Type

• What is the purpose of the generator?
• What fuel is easily available?
• Medium-voltage or low-voltage?
• NFPA 110 Required? Level 1 or Level 2?

Related: Sizing Commercial Generators

What is the Purpose of the Generator?

Is the generator a required (NPFA 110) source of emergency power, or a power source to keep the facility open and operating during a blackout or power outage? Maybe the company has an agreement with the local electric utility to operate on its own power during periods of exceptionally high demand, in which case it must power the entire facility as the primary source of power.

Very often, an industrial manufacturing facility must have both types of backup power.

National Fire Protection Association (NFPA) section 110 governs the rules for commercial and industrial generators that provide power for life and safety. A good example of NFPA 110 is a hospital backup generator for operating rooms, intensive care units, ventilators, and any equipment that keeps people alive, and where loss of power would result in serious injury or death. Many of those areas and equipment have a battery backup supply of power to keep them working without interruption until the backup generator takes over within ten seconds after the outage begins.

In a manufacturing facility, life and safety could refer to water pumps for fire fighting, ventilation systems for areas handling dangerous or noxious gases, and egress lighting can all fall under NFPA 110 Level 1 rules.

NFPA Level 1 Class 10 requires the generator to handle the full load within 10 seconds after loss of power. Level 2 generator Class 60 or 120 require transfer of load to the generator within 60 or 120 seconds.

For systems that are not life and safety related, such as manufacturing equipment, the generator may not operate automatically at all. It may require a manual start and transfer of load.

Fuel Choice

Diesel fuel is a logical choice for several reasons, but there are some drawbacks as well. Other options include Natural Gas, Propane, and Syngas.

• Diesel provides the most power per unit than any other easily available fuel.

• Diesel engines are simpler than spark ignited engines and therefore less prone to breakdowns.

• It’s not hard to size a diesel generator to accept the full load in a single step within the required response time. Gaseous fueled (propane, natural gas, synthetic gas) generators are prone to stalling immediately on startup when accepting a full load in a single step. This makes NFPA compliance more difficult, but not insurmountable.

• A diesel generator must have fuel available to run. An NFPA Level 1 Generator at a high seismic risk facility must have fuel storage capacity of 133% OVER the quantity of fuel required for running at full load for 96 hours without interruption. That can translate into hundreds of thousands of gallons of fuel. The fuel tank(s) may only store fuel for that generator. They can’t serve other facility purposes or even fuel vehicles.

• If resupply is not readily available, the storage requirement may increase from 96 hours (four days) to much longer periods, resulting in greater fuel storage requirements and costs.

• Natural gas and propane are options, but may require load sequencing, which may not be an option under NFPA 110 requirements for class U (uninterruptible power) or class 10 (10 seconds from outage to full load acceptance) systems, common for life & safety requirements.

• An option where diesel resupply is questionable or unreliable is a bi-fuel system that uses natural gas as a primary fuel with diesel injection as a backup/blend.

Related: Choose the Best Fuel for a Generator

For NFPA 110 level 1 class U or 10 generators, resupply must be a consideration. Local facilities must store adequate supplies for delivery and have the ability to deliver to their customers. In a disaster such as a hurricane, power outages can last days and weeks. Following Hurricane Sandy, utilities were unable to restore power to some customers for up to 5 weeks.

In areas with high seismic requirements like the West Coast or some portions of the Midwest, local authorities may be reluctant or simply prohibit natural gas as the supply for NFPA 110 generators. Liquid Propane and Diesel are the only options.

Medium Voltage vs Low Voltage

Anytime the power requirements reach 500kW-1MW or higher, the engineer designing the system will consider whether the site requires a medium voltage versus a low voltage service, and match the generator to those needs. From 500kW-1MW, the consideration will likely fall on whether the facility will utilize large motors and how many large motors it has. A single 200 HP motor requires a minimum of 160kW to run, and six times that amount during the first 1–3 seconds when it starts.

Medium voltage generators for industrial sites:

• 4160 Volts: Most common in the USA for data centers, petrochemical, and factories.
• 6.6kV / 6.9kV: Frequently found in heavier industrial sites.
• 13.8kV: Large industrial parks and oilfields

The short version here is that a medium voltage generator is more economically feasible than a low-voltage generator.

The choice falls on the basic power equation of Watts = Volts x Amps. At high voltages, the current required drops proportionally. A 2000kW generator at 480 volts is pushing out 3000 amps, requiring large parallel cables for each phase (3 phases) plus ground. It quite literally turns into a wall of cables with an enormous wiring cost and a panel of breakers near the limit of their capacity. The same generator operating at 4160 volts is only pushing about 350 amps, requiring a single, moderately-sized cable for each phase + ground.

We could say that 4160 volts the typical industrial standard voltage for any installation requiring more than 500kW to 1000kW (1mW).

NFPA 110 Generators

To delve into all the specifics of the NFPA 110 requirements is far too specific for this article and the question lacks the depth of detail necessary for a good answer.

The bottom line is, will the generator provide power necessary to life and safety?

• Critical power for life and safety: Level 1, typically Type 10.
• Critical power for manufacturing: Level 2, typically Type 60 or Type 120.

An NFPA 110 level 1 generator of Type (takes the full load within 10 seconds of an outage) is the requirement at hospitals. For industrial or manufacturing operations, Type 60 or 120 is common for loads that don’t carry life or safety risks.

There are specific systems within an industrial facility that may require a level 1 type 10 emergency power supply system. These systems may have life-safety systems that run on a different Type 10 generator.

Bottom Line

Any commercial generator or industrial generator installation requires an evaluation by a qualified individual or consulting company. Smaller installations up to 250kW may only need the advice of an electrician qualified and experienced in commercial electrical work. Industrial and large scale manufacturing facilities should engage the services of an electrical engineering consultant.

Your electrical engineering consultant will work with other consultants to ensure your facility has the emergency backup power system that it requires, including the generators for life and safety, and to keep the facility running during outages or blackouts.

Commercial Generators