Commercial Construction Considerations: Electrical Systems

In the past few articles, we have looked into several different building components including structure, HVAC, roofs, in addition to performance based design. One important building component that we have not discussed is the electrical system. This article will take a look at building electrical systems. We will also discuss some of the basics of utility electrical systems, but that topic is very important and is outside of the scope of this discussion.

Why is knowledge of a buildings electrical system important? The most vital is life safety. Coming into contact with the wrong components of the electrical system in the buildings where we fight fires, perform rescues, or provide EMS could lead to severe burns, and death. Most of the time these deaths can be easily avoided if we had a little more knowledge, paid a little more attention to what we were doing, or didn't try to get just a little bit closer to that power line.

The easiest way to discuss this topic is to start at the utility pole on the street. They are typically transmitting high voltage, from 4.5 to 13.2 kilovolts. This power is then transformed to one of several lower voltages for use in commercial buildings and homes.

Most commercial buildings use, 120/208 volt power or 277/480 volt power, while most homes use 120/240 volt power. The actual voltage that a facility uses is not overly important. However, it is a good piece of information to have.

The Basics
The transformers that convert the voltage are located in several places including utility poles, mounted on pads, or in some cases -- mostly in older facilities -- you can find them in the basement of a facility. These are very dangerous to personnel who are not adequately trained. Firefighting personnel should never open a pad-mounted transformer and should never use an aerial device to gain access to a pole-mounted transformer.

In addition to the electrical hazards, most transformers contain oil to assist in the cooling process. This oil should be treated as we would treat any other hazardous material. In addition to the cooling oil that is used today, you may still find polychlorinated biphenyls, or PCBs used as the cooling fluid in some older transformers.

These transformers should be clearly labeled which is why we need to remember to take a minute and think about what we are doing before we do it. As with any Class C fire, a transformer fire should be handled with a dry chemical extinguisher that is rated for Class C fires. When fighting these fires make sure you know what you are dispensing the dry chemical on. If the cooling oil is exposed, you will splash it, spreading the fire.

Once the power from the utility is transformed it then comes into the building or to the side of the building, where it is metered. This typically happens outside the building and then the power is routed to the main control point for the power.

The Main Control Panel
The device used as the main control point can be referred to by several different terms including, main disconnect, main circuit breaker, or main switchgear. Regardless of what it is called, this is the point in the system where the power to the entire building can be shut off. You should not assume that it will turn all of the power off. The only way to be sure that the power to the facility is completely off is to have the electric company disconnect the conductors feeding the facility. From the main switchgear, the power system continues to out to sub panels located throughout the facility, and from the sub panels to actual devices, lights and receptacles.

There are several items that you need to be aware of in the electrical room including the switchgear described above, conduits, transformers, and wire ways. Firefighters need to be very careful when operating in electrical rooms because of water use with exposed panels and exposed conduit. Many electrical rooms in commercial facilities are located in the basement or in a room below grade.

These rooms naturally attract water because of their location and after several years, underground conduits develop leaks that allow ground water to travel into the room through the conduits. Therefore, firefighters need to be aware of panels missing covers exposing their live buss bars and conductors. You do not need to be in contact with a live piece of electrical equipment for you to receive a shock. If you encounter a situation were there is a panel without a cover or exposed conductors, stay away until the power has been disconnected by the utility company, or a licensed electrician can assist.

Generators Are Now Common
Generators are a key piece of electrical equipment that we all need to be aware of. For many years, generators were only found on buildings that served a critical purpose such as hospitals, police, and fire stations. However, there has been a large increase in the number of buildings that have generators. You can find a generator in almost any facility including homes.

There are a few issues we need to consider with generators. The first is pretty basic. There are combustion engines using diesel fuel, propane, or natural gas to operate. The second is generators that are located indoors. Because they are combustion engines, they produce products of combustion that may not be exhausting properly.

The combustion concern in no different than the concern from HVAC equipment. The last concern in regard to generators is the automatic transfer switch. Many facilities utilize these switches so that downtime during a power failure is minimized. Just as their name implies, these transfer switches are automatic, so when utility power is lost the generator starts to run. The problem is you may think you are shutting off the power, and while you are disconnecting the utility power the generator is starting and feeding the system. Therefore, it is important that the power is disconnected by the utility and the generator is disconnected to be sure there is no power in the building.

So we have discussed some of the components of electrical systems that you will find in commercial facilities. As we all know, electricity kills and we need to make sure we remain safe. We have now discussed the all of the main building systems.

In the future, look for more information on utilities, gas, electric, water, and sewer and some of the key features of these systems.

As always, spend some time getting to know the facilities in your response area. It could be the difference between life and death.


MATTHEW STIENE, a Firehouse.com Contributing Editor, is a project manger for the Mecklenburg County Real Estate Services Department, and a firefighter with Robinson Volunteer Fire and Rescue, in Charlotte, NC. He is a licensed professional engineer in North Carolina, New York and Pennsylvania, and is a certified facility management professional. To read Matthew's complete biography and his archived articles, click here. You can reach Matthew by e-mail at mattstiene@hotmail.com.

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