At a commercial structure fire, it’s important that the truck companies assigned to securing utilities are familiar with utility hardware and the hazards associated with each system.
Occupancy type will usually drive the type, size, complexity and placement of utilities. Considering that the time and personnel needed to secure utilities are often underestimated, preplanning is the best way for truck companies to become familiar with the different systems in their first-due area, how to secure them and how long it will take.
Upon arrival at an incident scene, truck companies should put in an early request to the utility company to respond to the incident to help ensure that the utilities are secured. On occasion, complex systems may need to be secured by the responsible party of the occupancy or the power company.
As firefighters, we should know not only what we can shut off, but also what objects we must avoid. With that in mind, this article will address some of the most common electrical hardware that crews may encounter when at the scene of a commercial fire.
Commercial & Industrial Power Shut-Offs
Commercial buildings and strip malls have service entry cabinets, which are usually found in the back of the structure and may be marked with the utility company’s name. These cabinets contain a variety of shut-off configurations and may be marked with individual zones or suite numbers. The main power disconnects are in the same panel or adjacent to the meter. In strip malls, the anchor store may have its own main panel and several sub-panels.
There are three general types of disconnects: 1) fused or non-fused pull-out, 2) circuit breaker and 3) external lever. The external lever is the most common type in commercial buildings. It’s used to control single electric devices and will make a loud “pop” sound when turned off. (See photos, p. 39.)
Many buildings, especially the anchor occupancy in a strip mall, will have an electrical room with a utility company lock box. Most often, the Knox-Box keys on the truck won’t work on these exterior doors, as the box belongs to the utility company; however, there will be an interior door that’s accessible with a Knox-Box key. Although this door is safe to force open, it’s more effective and provides better customer service to pick another door in the rear and open it with a key to access the interior door to the electrical room.
The inside of this electrical room will contain main shut-offs as well as sub-panels. Here, it’s possible to shut off certain sections of the occupancy, while leaving certain zones on (i.e., coolers for food).
In smaller, isolated fires where securing the entire power to a strip mall may not be necessary, each individual occupancy may contain its own sub-panel that controls utilities for that specific business. These sub-panels will look like a residential panel, and each breaker should be labeled for the device(s) it controls.
Generators are often overlooked when securing utilities. Most commercial generators operate in the same fashion. Industrial generators store some type of fuel (most often natural gas or diesel), for the generator head that provides electrical current. These generators are usually hardwired permanently into the building’s electrical system.
When securing power, it’s important to know that once the power is secured, a back-up generator may also need to be secured. There are two ways to prevent a generator from delivering power to the structure: 1) shut off the generator or 2) shut off the breaker that feeds the building from the generator.
A generator usually has numerous doors in the housing with most often only one leading to the panel that enables the system to be secured. The door that usually contains the shut-off switches will be on the end of the cabinet, opposite of the exhaust. The exhaust is on the end of the cabinet that has no baffles (due to being soundproofed to help reduce the noise of the exhaust).
When securing the breaker, there are two types of generator transfer switches: automatic and manual. These systems are often driven by building code requirements and should be identified prior to a fire.
An automatic system turns on automatically and feeds power to the building from the generator when the main power has an outage or has been turned off. This back-up power must be secured to ensure that back-up power is not re-energizing the system. In a manual system, truck companies must ensure that the generator is not turned on, but no shut-off procedures need to occur.
Equally important as knowing what to shut off during a fire is identifying what will hurt us and what we should avoid. Electrical boxes are found everywhere and have no standard shape or size. Utility electrical boxes in particular are extremely dangerous and should not be opened, as there is no shut off within them.
Switching Cabinets: These boxes contain primary cables in and out, and are used to switch power on and off, much like a light switch. These boxes are usually the bigger electrical boxes on the property and may be controlled from a remote location by the utility company. If it’s safe to do so, obtain the number on the box to relay to the utility company. Important: Firefighters should avoid these boxes, as they have extremely high voltage and there is nothing for us to secure!
Transformers: Transformers step down electricity from primary to secondary voltage and feed into a service entrance cabinet or breaker panel. These boxes contain a high-grade mineral oil used to keep wires cool and are smaller than switching cabinets. These boxes come in different shapes and sizes and make a “buzzing” sound. They also have numbers on them that may be relayed to the utility company. Again, firefighters should avoid these boxes, as they are also very high voltage and there is nothing for us to secure.
Communication Cabinets: These cabinets come in a variety of shapes and sizes and are usually low voltage. If a meter is attached to these systems, we should assume it’s high voltage. There is nothing for firefighters to secure in the boxes, and they should not be opened up.
A Final Word
Securing utilities on commercial structures is not as simple as flipping one switch; it’s an involved task that requires preplanning and time. Technology is changing daily, and it’s therefore important that firefighters stay knowledgeable about new systems. Become familiar with building code requirements for your respective cities, as this will often drive how shut-offs are arranged.