What should be connected to an emergency generator in a commercial building?

Commercial buildings are characterized by the continuous presence of a large number of occupants, which means that security must be among the top priorities of the owner companies. When addressing the topic of backup generators, the New York Building Code classifies loads into two main categories: emergency loads and standby loads.

Emergency loads include building equipment and systems that would create life-threatening conditions if they stopped operating. For example, exit signs and stair lighting are always considered emergency loads, as it is very difficult to evacuate a building without them.

Standby loads may cause disruption or discomfort if they stop operating, but do not create risks such as those involved if an emergency load loses power. Keep in mind, however, that backup power for some backup loads is mandatory, especially loads that simplify troubleshooting during an electrical service outage or if they are useful for rescue operations during an emergency.

General Emergency and Backup Power Requirements for Commercial Occupancies in New York

Commercial buildings in New York City typically fall into one of the following occupancy classifications:

• Assembly groups A-1 to A-5, which include restaurants.
• Business Group B, which includes office buildings
• Educational Group E, which includes schools.
• Institutional Groups I-1 to I-4, which include hospitals.
• Grupo Mercantil M, which includes retail.

The New York Building Code provides a general list of emergency and standby loads for which standby power is mandatory, but there are additional requirements for the following occupancy groups:

• Assembly group A, all subgroups
• Business Group B and Educational Group E, where the building occupied space less than 75 feet above the lowest fire vehicle access and a gross area in excess of 15,000 ft2 per floor or at least 100,000 ft2 in total.
• Institutional Group I-3: Correctional centers and psychiatric hospitals
• Special requirements also apply to indoor shopping malls, high-rise buildings and underground locations.

The following table provides a list of all loads that must be connected to emergency power and standby power in commercial occupancies in New York. Specific requirements for some occupancies or building types are provided in the next section.

Emergency and Standby Power: Special Cases

The New York Building Code establishes additional requirements for some occupancy groups or building types. They are summarized in the following table, and remember that the general requirements still apply.

Optional standby power: additional requirements

All loads not included in the tables above are considered optional standby loads, meaning that the New York Building Code does not require a standby power system for them, but they may be installed anyway if deemed appropriate. It is important to note, however, that the following loads must be added to any optional standby loads when sizing the generator:

• Fire alarm systems
• Emergency light
• At least one elevator serving all floors, in buildings with occupied floors more than 75 feet above the lowest fire truck access

Although these loads are typically covered by emergency or mandatory standby power systems, the code requires that they be counted toward any optional standby system as a fail-safe measure. Additionally, the code allows fuel supply to be shared between optional emergency and standby generators. Additional equipment required for generator operation can also be shared between emergency units and optional standby units.

When is optional standby power recommended?

There are many loads in commercial buildings that are not legally required to have backup power. When determining what to connect to an optional backup power system, the best recommendation is to work closely with the property owner and use common sense.

Cooling systems

When refrigeration systems stop working, it is only a matter of time before the products and supplies they contain begin to degrade. This may not be a critical problem in an office building that has just a few small refrigerators, but it can have serious consequences in a restaurant or hospital where large quantities of food or medical supplies require low-temperature storage.

In these cases, even if a backup power system is not legally required, it is in the company's best interest to install it. In both cases, the omission of the backup power system can have consequences for human health. Furthermore, even if spoiled food or medical supplies are discarded, it represents a financial loss for the company.

Water pumping systems

Water supply is a fundamental building system, especially when there are kitchens and bathrooms. Therefore, optional backup power is recommended if the building relies on a water booster pump; otherwise, an interruption in electrical service will cut off the water supply to upper floors.

Network infrastructure

Information technologies are fundamental to modern business operations and generally represent a small energy expenditure compared to equipment such as water heaters and HVAC units. Lack of connectivity can severely disrupt business operations and, in hospitals, can even reduce the ability of medical staff to care for patients.

Air conditioning

Providing optional backup power for air conditioning systems can be expensive as the required generator capacity increases significantly. However, there are many cases where the loss of air conditioning can be very disruptive to business operations and the additional cost may be justifiable from a business perspective. For example, the loss of air conditioning can drive away potential customers in restaurants and retail stores.