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Electrical Wire and Cable

How to Add a Light Fixture

Can I tie into an existing light fixture to add a new one?

Home Electrical Wiring Video

Hooking Up a Generator to the House Panel
Using a Circuit Breaker Interlock Kit
for Backup Power

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Adding a Light Fixture

Electrical Question: Can I tie into an existing light fixture to add a new one?

Light Fixture Wiring

How to add a Light Fixture


Application: Light Fixture Wiring.
Skill Level: Beginner to Intermediate. This electrical wiring project is best performed by a Licensed Electrical Contractor.
Tools Required: Basic Hand Tools and Safe Ladder.
Estimated Time: Depends on personal experience, the type of light fixture and access to the fixture.
Precaution: Identify the light fixture circuit, turn it OFF and Tag it with a Note before working with the wiring.
Notice: Replacement parts for the light fixture should be compatible with the type of  fixture that has been installed.

Dave’s Reply:

The Light Circuit Wires
Because the fixture box has 4 black and 4 white wires does not mean the circuit is overloaded and the circuit should be protected by an appropriate breaker or the fuse at the electrical panel.

The Light Circuit Load
In order to determine your circuit capacity, we have to identify the wire gauge of the circuit (not the wires of the fixture). Typically this would be a #12 which is rated for 20 amps, or #14 rated for 15 amps, #14 being smaller that the #12.

Identify the Light Circuit at the Panel
Next you need to identify this circuit at the electrical panel that supplies the power, with is either a circuit breaker or a fuse.

What Else is On the Light Circuit
Next, find out what devices (lights, plugs etc.) are on this circuit. Make a list of these devices and make note of the power that is being consumed. Simply make a list of the number of light bulbs and the watts of each bulb. If there are receptacles on this circuit, make note of the items that are typically used. Look for name plates that state watts or amps. You need to convert this total number into amps or watts.

Convert Watts to Amps for Lights
To determine watts take 120(volts) times the amps. To determine amps divide watts by 120(volts).
Then we determine 80% load factor so we do not overload the circuit:
So a #12 gauge wire can be safely loaded up to about 17 amps or 1920 watts, and a #14 gauge wire can be safely loaded up to about 12 amps or 1440 watts.

What is the Proposed Additional Light Fixture Load
Of course you need to take your proposed light fixture into consideration, and the ceiling fan, and don’t forget to deduct the original light fixture you would be removing. Also, keep in mind that we understand that the circuit will most likely never have all these devices turned on all at the same time, however we do want to identify the circuit potential load and keep the load below the maximum allowed. The circuit wiring is protected by the breaker or the fuse, and this is why we should never replace these protective devices with oversized circuit protection, but stay with the right size breaker for the wire size.

More Considerations about the Light Circuit
Ok, now that we have that out of the way, I have some things for you to consider. If you determine that your circuit will in fact allow you to add the ceiling fan, you need to make certain that the ceiling support box is in fact rated for the weight of a ceiling fan.

The Light Fixture Box
These boxes are identified with a stamp or printing stating their compliance for ceiling fans. If you are not sure, I would encourage you to replace the box with an approved box, and install wooden blocking between ceiling supports if needed. (I will be placing info about these methods on the website soon.)

Access to the Light Circuit Wiring
If you do not have access to the ceiling you may purchase an approved metal fan box kit which comes with an adjustable spanning bar, and follow the directions provided.

Light Circuit Electrical Safety
As always, positively identify your circuit and never work on an energized circuit, or perform any work where you do not feel comfortable or lack experience. It’s always best to hire a qualified licensed electrician to insure best results.

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Understanding electrical junction boxes and what they are used for. Home electrical wiring is the process of installing electrical wire to a location that will serve electrical devices or an appliance. One very important component is the box where the wire will be installed. The type and size of the home wiring electrical boxes will depend upon the circuit size, application and its location.

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Dave's Guide to Home Electrical Wiring:

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Wire It Right with the help of my Illustrated Wiring Book
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Complete Guide to Home Electrical Wiring

Perfect for Homeowners, Students,
Handyman, Handy Women, and Electricians
Wiring GFCI Outlets
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120 Volt and 240 Volt Outlet Circuits
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Learn more about Home Electrical Wiring
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Be Careful and Be Safe - Never Work on Energized Circuits!
Consult your Local Building Department about Permits and Inspections for all Electric Wiring Projects.

Electrical Tips to Help You Wire it Right

The Safest Way to Test Electrical Devices and Identify Electric Wires!

The Non-Contact Electrical Tester
This is a testing tool that I have had in my personal electrical tool pouch for years, and is the first test tool I grab to help identify electrical wiring. It is a Non-contact tester that I use to easily Detect Voltage in Cables, Cords, Circuit Breakers, Lighting Fixtures, Switches, Outlets and Wires. Simply insert the end of the tester into an outlet, lamp socket, or hold the end of the tester against the wire you wish to test. Very handy and easy to use.

The Quickest Way to Check for Faulty Electrical Wiring!

The Plug-In Outlet Tester
This is the first tool I grab to troubleshoot a problem with outlet circuit wiring. This popular tester is also used by most inspectors to test for power and check the polarity of circuit wiring.
It detects probable improper wiring conditions in standard 110-125 VAC outlets Provides 6 probable wiring conditions that are quick and easy to read for ultimate efficiency Lights indicate if wiring is correct and indicator light chart is included Tests standard 3-wire outlets UL Listed Light indicates if wiring is incorrect Very handy and easy to use.

Strip Off Wire Insulation without Nicking and Damaging the Electric Wire!

The Wire Stripper and Wire Cutter
My absolute favorite wire stripping tool that I have had in my personal electrical tool pouch for years, and this is the tool I use to safely strip electrical wires.
This handy tool has multiple uses:
The wire gauges are shown on the side of the tool so you know which slot to use for stripping insulation.
The end of the tool can be used to grip and bend wire which is handy for attaching wire onto the screw terminals of switches and outlets..

The wire stripper will work on both solid and stranded wire. This tool is Very Handy and Easy to Use.

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