How to Properly Read Electrical Blueprints

Electrical blueprints have many symbols.

Blueprints are architectural tools used by professionals for design and planning. Blueprints are hand drawn or created using special software to display detailed information on building dimensions. Electrical blueprints are either embedded within primary blueprints or created as standalone documents. The purpose of the electrical blueprint is to show the logical layout of a structure's electrical components, including power outlets, circuit breakers and lighting. Blueprints use numerous lines and symbols to represent various devices. Fortunately, reading electrical blueprints is similar to reading a map; you must use the legend included with the document to decipher symbols that are used.

Things You'll Need

• Electrical blueprint or schematic

Instructions

1. Find the blueprint legend. The legend is your key to the variety of industry-specific electrical symbols used throughout the diagram. It is typically located on a corner of the diagram. Review the symbols in your blueprint's legend, as these are the symbols used throughout the rest of the blueprint. Standard symbols include a shape for electrical outlets, usually a circle with three lines, lights, usually circles with lines projecting from the center, and appliances, usually a combination of circles and other shapes along with initials like "CT" for cook top.

2. Start in one section of the electrical blueprint, such as the foyer, and take note of each symbol represented in that space. Match the symbol in this section with the blueprint legend to identify its function. Certain symbols are apparent, depending on where they are on the blueprint diagram. For example, symbols on the part of the blueprint that represents the front door depict a doorbell, which resembles a square attached to a stick, or a generic porch light, a circle with protruding lines.

3. Follow white or black solid lines from one symbol to another. This shows how electrical transmission lines are wired throughout the house.

4. Check for numbers enclosed in a circle on the diagram. These are used to identify a cross-section of the room, which is found on another page of the blueprints where electrical lines lead. For example, if you see an encircled "4" on page one, that section of the room is labeled with an encircled "4" on page two (or any other page) that shares electrical components with the room on page one.

5. Look for thick solid lines, which represent full-height walls. Also look for thin solid lines, which symbolize built-in structures. This aids in your understanding of where electrical components are placed and connected. For example, a switch in a thin solid line in the schematic bedroom can indicate the power switch for a motorized TV stand.

Tips & Warnings

• Refer to your blueprint legend. There are dozens of electrical symbols used by electricians and engineers for schematics, but a small and specific subset are in use for any one set of blueprints.

• Consult a standard electrical blueprint symbol reference (see Resources) if no legend is available.

References

• Learn C: Tutorial -- How to Read a Schematic
• Integrated Publishing: Reading Electronic Diagrams and Schematics
• Eplans: How to Read Blueprints

Resources

• Read this Article in Spanish
• The House Plans Guide: Electrical Blueprint Symbols