The Commercial Power System
The power system for a commercial space begins with the municipal grid and ends with the electrical panel in the building. The panel board contains wiring and circuit breakers that serve devices in the facility, ranging from lights to equipment for manufacturing.
The panel may also contain an ATS or an Uninterruptible Power Supply (UPS) system. ESP and UPS systems differ in their ratings and function.
Power Distribution
Commercial buildings typically require a higher level of power distribution than residential properties. Having sufficient capacity to support the load demands of all equipment in the facility is important. Additionally, regulations may place requirements on the system that aren’t required for residential systems, such as emergency egress lighting and fire alarms.
The electrical distribution system starts at the power company’s utility pole and transports high voltage electricity to a transformer where it is adjusted down for distribution. It’s then delivered to the building through a main distribution panel and/or utility closet. From there, the supply wires connect to a meter and then to a bus where it is split into several circuits that feed individual consumers inside of the building. The distribution bus is connected to regulator banks that prevent an excess or deficiency of voltage as it delivers power to the end users.
In many cases multiple customers share a common transformer and power infrastructure within a complex or industrial park. This can be due to reduced demand for power, the cost of purchasing a power transformer or space constraints. A load-flow study helps to determine the ability of the system to satisfy a load and if it can be operated at lower cost.
A system one-line diagram, defined in IEEE 315, is a map that shows, by means of single lines and graphic symbols, the course of electric current through a Commercial Power System circuit or a group of circuits. This is a crucial part of the design process for electrical systems.
Backup Power
The high reliance on power in commercial facilities makes emergency standby power a necessity. From computers that maintain massive loads of financial information to manufacturing equipment that generates profits, critical systems need sustained power to stay operational during a power outage. If they don’t, the effects can be devastating.
For example, a hospital needs backup power to maintain life safety systems such as fire alarms and elevators in the event of a normal or extended outage. The National Fire Protection Association (NFPA) 110 standard, as well as the Joint Commission on Accreditation of Health Care Organizations, dictates that a hospital must provide power to life-safety devices within 10 seconds of the loss of utility power. This requires a generator sized to meet the specific load of each device in the facility.
Additionally, sensitive instruments may require uninterruptible power supplies to keep them from being shut off by the transfer switch when a generator comes on line. A load study is recommended to determine which devices will be backed up by the generator and which will receive priority from an uninterruptible power supply.
Regardless of the size of your facility or its critical systems, you need Commercial Power System a plan in place to deal with both short and long-term blackouts. Contact a local commercial electrician to learn more about designing a safe, reliable, and efficient power system for your property.
Lighting
Lighting is one of the largest end uses of electricity in commercial buildings. In 2012, it accounted for 17% of all commercial building site electricity use, down from 21% in 2003. The share of lighting energy use in smaller commercial buildings has not changed much since 2003, but the overall trend has been a decrease in lighting demand due to the adoption of more efficient lighting technologies and controls.
Lighting control systems are used to reduce power usage by dimming or turning off lights when spaces are unoccupied. The most common types of control devices include occupancy sensors, which turn lights off or down when the space is unoccupied, and scheduling, which controls lighting power based on an established schedule. Occupancy sensors were reported in 16% of all lit buildings and 55% of large (more than 50,000 square feet) lit buildings.
Three-phase power is more reliable than single-phase power because it provides an uninterrupted flow of current, eliminating the possibility of a flickering light bulb caused by voltage drops. It is primarily used in large, heavy loads that might otherwise cause single-phase circuits to fail, such as motors on sizable commercial air conditioners or drive systems for mechanical systems.
With significant strides in technology, advanced lighting system upgrades are among the most cost-effective and energy-efficient ways for a commercial power system to cut operating costs and improve occupant comfort and productivity. This playbook outlines lighting system fundamentals, tips for selecting lighting fixtures and control systems, and strategies to maximize daylight.
HVAC
The HVAC system in a commercial power system helps to control the indoor climate in a building. The size and type of HVAC system varies depending on the requirements for each space. In most cases a contractor will estimate the capacity needed and then design, select, and install the system. Building inspectors will then inspect the installation to ensure compliance with local codes.
Most power systems use alternating current (AC) electricity. The electricity moves through conductors from the power company’s meter to the building panel board, which may be located in a utility closet. From there, the circuits branch out to the various sub panels that serve the building’s equipment, lights and receptacles. Conductors are also labeled as high or low voltage in order to identify which ones carry the highest and lowest amount of energy.
A large three-phase system is often used in commercial applications because it allows for greater load capacities. Unlike single-phase AC, which has one voltage peak per cycle, a three-phase system has three peak voltages occurring simultaneously over a 360° cycle. This gives a much more stable current that can handle the higher loads. When one leg of a three-phase system is supplying less current than the other two legs, it is considered an imbalance. This can cause the equipment to malfunction or even fail, if the imbalance is extreme.
