The electrical plan or plans for a commercial building are one of the primary mechanical plans that are required for construction. The other primary mechanical plans are for plumbing and heating/ventilating/air-conditioning. Secondary mechanical plans are created for communications and safety/security.

The process of laying out electrical plans for a small commercial building is comparable to the designing of a residential structure with a few variations. A residential structure usually requires a 240/120 volt, 100 amp service (larger houses may require a 200 amp service). Since commercial buildings usually involve more occupants and/or visitors and a wider range of activities that require higher amounts of electricity, most start with a 440/220/110 volt, 150 amp service and go up from there depending on square footage and the type and quantities of equipment.

The first step in the process of designing a commercial electrical system is to create a "Riser Diagram" that shows the amounts of power and the basic components that control and distribute the power throughout the building. A "Riser Diagram" includes:

1. Transformer that sits outside of the building usually on the ground at the property line or on a pole. The transformer controls the voltage provided to a building. The primary service would provide 440/220/110 volts and a secondary service would provide 24 or 12 volts for low voltage lighting.
2. Electrical power enters a building through an electric meter that attaches to a panel on the exterior wall of the building usually at the rear of a building. The meter is also the point where the electrical system is grounded using a 1/2" or larger diameter copper rod that is driven into the ground.
3. From the meter, electrical powers enters the building through a master switch or series of master switches depending on the size of the building and the number of stories.
4. Power is then directed to a distribution panel which act like a large circuit breaker where power is directed to any number of circuit breaker panels or to sub-distribution panels on multiple storied buildings.
5. Circut breaker panels may be located near the distribution panel or may be placed in closets in other parts of the building or on upper floors. Multiple circuit breaker panels are used to control power to outlets, lights, fans, motors, etc.

The process for laying out plumbing plans for a small commercial building requires the development of TWO drawing sheets. One sheet is for the supply system that shows how water is enters the building and how the water is distributed to fixtures such as heaters, sinks, showers, fountains, sprinklers or faucets. The second sheet is for the waste system that shows how waste water or sewage is directed away from fixtures and from the building.

The supply system includes a pressure regulartor to maintain a constant water pressure; a meter to measure water usage; a heater or boiler to provide hot water; filters to remove minerals and purify drinking water; and copper piping of various sizes to maintain pressure throughout the building. A variety of fittings are used to contol the of flow water: valves, elbows, reducers, tees and caps. Risers should contain air, act as a shock absorber and are placed near outlets to reduce "water hammer", the sound that occurs when faucets are shut off quickly.

The waste system includes traps to keep gases from entering the building; vents to allow gases to leave the building; clean-outs to allow cleaning of lines; removable caps to allow access to lines; check valves to keep sewage from backing up into a building and PVC or cast iron piping of various sizes to allow for uniform flow of wastes.