How to Read Electrical Schematic Blueprints

Written by tammy bronson
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How to Read Electrical Schematic Blueprints
More than one phase of construction is read on a single blueprint. (compass on blueprint image by FrankU from

Interpreting an electrical blueprint is simple if you know what the symbols and numbers mean. A typical electrical schematic blueprint shows the type of power and the layout of power entry into a building. The purpose of the blueprint is to tell people what to do and in what order. There is more than one schedule going on simultaneously in constructing a building. A few examples of schedules include how and when to make a panel board, a connected-load and fixture installation. In order to read a blueprint you need to know the language.

Skill level:


  1. 1

    Find the symbol legend on the blueprint. The symbol legend shows you the path of wiring throughout the building and room by room. Find the number written by each wire on the blueprint. The number represents which breaker the appliance or light will run to.

  2. 2

    Study the symbols associated with electrical wiring from the symbol legend. Standardised symbols are used on all blueprints. A straight line will symbolise the electrical wire. Letters are frequently found in circles to symbolise devices. An "A" inside a circle on the wiring diagram represents for an ammeter, a "V" in the circle is a voltmeter, a "W" is a wattmeter and a "G" is a galvanometer. Some symbols, such as electrical sockets, resemble the real device. See Resources for electrical blueprint symbols. Ask a certified electrician if you can't figure out what a symbol represents on the blueprint.

  3. 3

    Look for room names on the blueprint. Each room has the same wiring pattern, but outlets and fixtures map out differently.

  4. 4

    Check to see if all appliances have separate breakers. Decide if the blueprint shows phasing. Phasing is grouping lights and appliances in an area of a building on one line. This is a personal preference decision for the electrician.

Tips and warnings

  • Review the lighting plan. The lighting plan tells you the types of fixtures going into the building and the order of installation.
  • Never overload a breaker; this is a fire hazard.

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