5 Common Electrical Symbols All Builders Need to Know
Jul 16, 2020
Heating and air-conditioning systems, plumbing, electrical outlets and wiring (including lighting), and other mechanical systems are typically detailed in MEP (mechanical, electric, plumbing) plans, and installed by specialists in their field. While builders don’t need to understand everything in the MEP plans, builders should be aware of how these systems will operate and where the wires and pipes will be placed.
Architects also include information about outlets and switches in their power and data plans—which are part of the blueprints package—though these are generally not as comprehensive as MEP plans. Some elements of these plans will have more direct implications for builders as recessed lighting, ceiling fans, and features that have to be blocked (surrounded by a small frame) for support.
Of the different systems on MEP plans, you’ll want to pay special attention to the electrical elements and their placement. Jordan Smith explains in his Introduction to Reading Blueprints course:
“The homeowner is going to interact with electrical much more than they’re going to interact with things like plumbing lines or HVAC ductwork. There’s going to be many points throughout the house where the homeowner’s going to interact with light switches, with appliances and other things that are fed through the electrical system. So the architect pays a lot of attention to the electrical design.”
While installation of the wiring and outlets will be left to an electrician, here are common blueprint symbols. These will typically also be listed in a legend, so it isn’t necessary to memorize them all.
Common Electrical and Lighting Symbols
A circle off of the wall and connected to it by two parallel lines represents a typical outlet (or receptacle) with two sockets. Abbreviations and numbers next to the duplex provide additional information.
For example, GFCI indicates a ground-fault circuit interrupter (an outlet with a built-in fast acting circuit breaker that prevents electric shocks and will typically be used with outlets near water, in bathrooms and kitchens). The number 220 next to a duplex indicates it’s a 220-volt outlet, commonly used for appliances that require 220 volts, like ovens and dryers.
Finally, if you see a square around a duplex or a quad (that is an outlet with four sockets) that indicates it’s a floor receptacle.
2. Lights and fans
The basic symbol for most lights is a circle and, as with duplexes, variations on how it is drawn and abbreviations next to it convey additional and essential information. The key on the floor plans will explain the particular symbols used on any project.
For example, half of the circle may be shaded black to indicate it’s an LED wall washer; the letter W next to it indicates it is intended for a wet area (like a bathroom). A recessed light is sometimes represented by a diagonal slash across the circle, though in other plans the letter R next to the circle is used to indicate that it should be recessed.