Commercial buildings are characterized by the continuous presence of a large number of occupants, which means safety should be among the top priorities for the companies that own them and the electrical engineers involved in their maintenance. When addressing the topic of backup generators, there are two main categories: emergency loads and standby loads.
Emergency loads include the equipment and building systems that would create life-threatening conditions if they stop operating. For example, exit signs and staircase lighting are always considered emergency loads, since evacuating a building without them is very difficult.
Standby loads may cause inconvenience or discomfort if they stop operating, but do not create risks like those involved if an emergency load is left without power. Keep in mind, however, that backup power for some standby loads is mandatory, especially loads that simplify troubleshooting during an electric service interruption, or if they are useful for rescue operations during an emergency.
Optional Standby Power: Additional Requirements for Electrical Engineers
Not all loads are considered optional standby loads, which means the building code does not require a backup power system for them, but it can be installed anyway if considered appropriate by the owner and electrical engineers designing the system. 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 lighting
- At least one elevator serving all floors, in buildings with occupied floors more than 75 ft above the lowest fire truck access
Although these loads are normally covered by emergency or mandatory standby power systems, the code requires them to be counted for any optional standby system as a failsafe measure. In addition, the code allows the fuel supply to be shared among emergency and optional standby generators. Complementary equipment that is needed for generator operation can also be shared among emergency and optional standby units.
When Is Optional Standby Power Recommended?
There are many loads in commercial buildings that are not legally required to have standby power. When determining what to connect to an optional standby power system, the best recommendation is working closely with the property owner and using common sense.
When refrigeration systems stop operating, it is only a matter of time before the products and supplies they contain start to degrade. This may not be a critical issue in an office building that only has a few small refrigerators, but can have severe consequences in a restaurant or hospital, where large amount of food or medical supplies require low-temperature storage.
In these cases, even if a standby power system is not legally required, it is in the best interest of the company to install it. In both cases, omitting the standby power system can have human health consequences. In addition, even if spoiled food or medical supplies are discarded, it represents a financial loss for the company.
Water Pumping Systems
The water supply is a key building system, especially when kitchens and bathrooms are present. Therefore, optional standby power is recommended if the building relies on water booster pump; otherwise, an electric service interruption will cut the water supply for upper floors.
Information technologies are key for modern business operations, and they generally represent a small energy expense compared with equipment such as water heaters and HVAC units. Lack of connectivity can disrupt business operations severely, and in hospitals it can even reduce the medical staff’s ability to serve patients.
Providing optional standby power for air conditioning systems can be expensive, since the required generator capacity is increased significantly. However, there are many cases where the loss of air conditioning can be very disruptive for commercial operations, and the extra cost may be justifiable from the business standpoint. For example, the loss of air conditioning can ward off potential customers in restaurants and retail stores.
In conjunction with the owner of the establishment, electrical engineers must consider all of the elements listed above – perhaps even more, if the situation calls for it.