Does your building have a good critical response plan? Every facility needs one. In fact, some local laws require more than one plan for different sorts of emergencies. Part of a good emergency response plan is an understanding of your building’s systems.
Current national electrical safety guidelines call for up-to-date information about your building’s electrical system. Incomplete or inaccurate information about electrical systems can cause injury or death. Often, electrical plans differ widely from the plans used at construction.
Emergency incident response depends on accurate information about the building and its hazards. Your building single line diagram is a critical part of building safety.
What Is a Single Line Diagram?
A single line diagram is a roadmap of the main components of your electrical system. It uses single lines and graphic symbols. These illustrate the course of an electric circuit or system of circuits.
The diagram includes the component devices or parts used in the circuit. It includes all redundant and spare equipment in the system. It shows the distribution path from the power source to each piece of equipment.
It includes circuit conductors and protective devices. The diagram includes all of the ratings and sizes of each piece of equipment.
Refer to Codes and Regulations
Safety regulations in the U.S. refer to these important documents:
- NFPA 70, The National Electrical Code
- NFPA 70B, Recommended Practice for Electrical Equipment Maintenance
- NFPA 70E, Standard for Electrical Safety in the Workplace
All electrical systems in the U.S. are uniformly bound by these codes. Building management and emergency workers depend on the protections mandated.
These codes work together. They define what belongs in a single line diagram. They also specify the systems, safety and analysis procedures for electrical circuitry.
Key sections of NFPA 70E that refer to the single line diagram include:
- 120.2, Lockout/Tagout Principles
- 120.5, Process for Establishing and Verifying an Electrically Safe Work Condition
- 130.5 (G), “The incident energy analysis shall be updated when changes occur in the electrical distribution system that could affect the results of the analysis. The incident energy analysis shall also be reviewed for accuracy at intervals not to exceed five years.”
- 205.2, Single Line Diagram
- 340.5, Specific Measures for Personnel Safety
- E.3, Typical Electrical Safety Program Procedures
NFPA 70B calls out the single line diagram in Section 6.2.2. Every electrical maintenance program depends on accurate, complete and contemporary information.
Section 126.96.36.199 gives the recommendation that the diagram shows all electrical equipment in the power system with ratings for voltage, frequency, transformers impedance, and protective devices.
Why Update and Review Regularly?
Needs and equipment can change between planning and placement in service. Loads get added or removed, safety equipment changes or redundancies disappear. These small changes aren’t a problem until a small change causes a major failure.
An updated single line diagram provides a concise map of equipment, redundancy, and protection. Regular updates with each change are necessary, no matter how minor.
These documents form a foundation for the work of many other related functions.
- Workers use the documents to create safe lockout/tagout situations
- Vendors use the documents to bid accurately
- The law requires them
- Designers and engineers determine plant expansion based on them
Modifications to the power system can form hazards. Changes in motor or transformers can create larger than expected fault currents. Any over-current protection devices applied over their rating can fail without warning.
The documentation is also used for efficient maintenance scheduling, safety evaluations and more.
Where Do You Get a Single Line Diagram?
The diagram begins with the building designer and engineer. As the building contractor installs equipment, the first adjustments and markups occur. At the end of the building process, as-built diagrams pass to an engineer for final review.
The building user conducts regular surveys to maintain the as-built diagram. At a minimum, a review of the diagram by a qualified engineer should happen every five years. A single line diagram is maintained throughout the building occupancy.
Elements included in a single line diagram include:
- Equipment inventory
- As-built drawings and diagrams
- Load confirmation connection to backup/emergency feed
- Identify single failure points
- Critical equipment redundancy design
- Widely distributed drawings (each facility, emergency responders, central off-site location)
In addition to emergency planning use, single line diagrams have daily use as well. The information in the document informs maintenance and replacement schedules. It provides troubleshooting for over-capacity circuits.
When the Diagram is Out of Date
The building designer works with a qualified electrical engineer to document the electrical needs of the building. From these plans, the contractor builds and installs the system.
The contractor consults with an engineer to document changes made during construction. The business owner receives the complete as-built diagrams.
Once the building is turned over to the user, a regular review by a qualified engineer is good practice. For many buildings, neglect of the line diagram is due to a lack of personnel or knowledge. A few simple steps can keep a building single line diagram correct and up-to-date.
Make notes of the changes on an existing copy of the diagram. Conduct a periodic survey to correct the diagram. A qualified engineer can perform the survey and provide an updated single line diagram every few years.
Find a Qualified Engineer
You need not keep an engineer on staff at all times to keep your single line diagram up to date. Bring in an engineer to update your diagram periodically. Use the information to keep emergency response plans relevant. Up-to-date safety procedures depend on accurate single line diagrams.
Complete your electrical circuit survey and single line diagram update project with an independent contractor. Start with whatever existing documentation you have. Determine the scope of your project like any other regular building maintenance and get competitive bids.
Complete information is critical to good emergency response plans. Don’t put off documenting your electrical systems. An engineering professional can complete updates on your diagram and troubleshoot problems. Contact us today to find the right electrical engineer for your needs.