How to plan house wiring

Written by cathy douglas
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Whether you are building a new home or remodelling an existing home, an electrical plan is essential. If you are not familiar with the principles of electricity, you will need to learn this skill, either by reading a book, taking a class or finding a mentor. Electricity is not hard, but it is dangerous--advance preparation can save your life. In an existing home, you have the luxury of knowing where outlet or lighting deficiencies are. You must consider your needs and wants, and take into account electrical code and proper wiring technique when planning your home's wiring.

Skill level:
Moderately Challenging

Things you need

  • Instruction book or class
  • Tape measure
  • Graph paper or software program
  • Plan drawing paper (24 by 36 inches)
  • Pencil

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  1. 1

    Attain the necessary knowledge to understand home wiring. Consult your local code rules to check if there are additions to the national electrical codes. If you are working on an existing home, decide if you are going to remove wall material, or if you are going to run wire through existing walls. This may make a difference in your outlet and light switch placements. Walk through the area, if possible, and get a feel for where you need lighting, what type of lighting you wish to have, how a room will be used, furniture placement, where outlets need to be.

  2. 2

    If you do not have a drawn house plan, you must draw one. Measure the outside of the house and sketch the basic footprint of the house. Include measurements in your sketch. Next, go inside the house and measure each room. Draw the walls on your sketch, including measurements. If you are planning lighting for the ceiling, do a diagonal measurement--from corner to corner--both ways. This will create an X and identify the centre of the room.

  3. 3

    Begin adding outlets, switches and lighting on a copy of your drawing. Keep the original to make copies for revisions. Draw the minimum number of outlets and switches you need to meet code. Use proper electrical symbols.

  4. 4

    Analyse your needs vs. what is necessary to meet code. You will likely want more outlets and switches. Make sure all of your outlets are accessible, and that there are enough outlets. Check the switch locations to ensure they are on the side of the door that opens. Whether you do the wiring, or hire someone to do it, the planning stage is the time to make any changesyour drawing will be used to wire the house.

  5. 5

    Redraw your house dimension sketch, including all exterior and interior walls on plan drawing paper, or create a plan drawing with software and print on a large scale printer. Figure out your scale. Each square will equal 1 or 2 inches or more, depending on the size of your home. Add your electrical switches, outlets and lighting to the drawing, using the proper electrical symbols.

  6. 6

    Determine how many circuit runs you will need. Circuit calculations depend on the size of the breaker, and the wattage of the item being switched or plugged in. If you have a 15 amp breaker on a 120 volt run, the maximum wattage available is 1800 watts per breaker. You can only use 75 to 80% of this before a circuit will trip. Each circuit run needs to add up to less than 1350 watts. A good rule of thumb is to keep each circuit to 7 to 10 switches or outlets. If you have a high-wattage appliance or light, reduce the number of switches or outlets on the run. Some items must have a dedicated circuit run to meet code.

  7. 7

    Draw a line connecting each switch or outlet on the circuit run. Once you have the rough drawing done, and are satisfied with the number of switches and outlets on each circuit run, have a licensed electrician check the drawing if you wish.

  8. 8

    Submit the drawing to your local building agency if it is necessary to get a permit.

Tips and warnings

  • There are many variations in wiring, especially lights, if you wish to use multiple switches for one light, or multiple lights on one switch. A good instruction book can walk you through these many variations.
  • Use a voltage probe or other tester to make sure outlets or switches are turned off before you perform any work on them.
  • If you are hand drawing, it is much easier if you use paper with a grid.
  • Make sure the breaker or electrical main is turned off while you are doing any electrical work. You may receive a severe electrical shock if you touch electrical sockets, wires or the breaker panel.

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