Install Wiring for a Second Light Fixture
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How to Install One or More Light Fixtures to an Existing Light Fixture: Wiring for More Light Fixtures, Preventing Circuit Overload by Calculating the New Circuit Load, Locating the Power Source, Making the Electrical Wiring Connections. © By: Dave Rongey |
Guide to Adding a Light Fixture
Electrical Question: I’m attempting to add a second light fixture to an existing wiring run, which currently has a single fixture attached to a single pole switch.
- The power currently comes into the fixture. I’d like to avoid replacing the wire that’s run to the switch if possible, which is 12-2, and simply pass the hot through the new second fixture to the switch. Is this possible?
- The wiring configuration would have the power entering on the far left, and the switch located on the far right.
Any help would be greatly appreciated!
This home electrical wiring question came from: Troy, in Poland, Ohio.
Dave’s Reply:
Thanks for your electrical wiring question Troy.
How to Install One or More Light Fixtures to an Existing Light Fixture
Skill Level: Intermediate to Advanced. This electrical wiring project is best performed by a Licensed Electrical Contractor or Certified Electrician.
Tools Required: Basic Electricians Pouch Hand Tools, hole saw and drill motor, drop cloth, a Voltage Tester and a fiberglass ladder.
Typical Materials Required: Type NM Cable or same type and gauge cable as the existing light circuit cable, staples for securing the cable, light fixture cut in box or required well supported fixture box for the specific light fixture, wire connectors.
Estimated Time: Depends on personal level experience, ability to work with tools, access to the circuit wiring and project area, and experience working with light circuit wiring.
Precaution: Identify the panel lighting circuit, turn it OFF and Tag it with a Note before working with the wiring.
Notice: Modifying or installing additional electrical wiring should be done according to local and national electrical codes with a permit and be inspected.
- Wiring for More Light Fixtures
- Adding one or more light fixtures when there is an existing fixture and switch is relatively easy when you understand the wiring that is necessary.
- Find out how much power the new light fixture(s) will require by counting the number of lamps and the watts for each lamp, then determine the total power required.
- Convert watts to amps with this calculation: Watts divided by 120 Volts = Amps. Example: 600 watts / 12o Volts = 5 Amps
- Preventing Circuit Overload by Calculating the New Circuit Load
- As a rule, electrical circuits are not loaded beyond 80% of the circuit rating.
- Identify the circuit which the additional lights are planned to be added to. Note the amperage rating of the circuit breaker and keep the 80% rule in mind.
- Turn on all the light fixtures that are on this circuit.
- Measure the existing load of the circuit using a clamp on amperage meter.
- Add the additional proposed load of the new light fixtures to the existing load and determine the load percentage.
- To calculate the Percentage of Circuit Load take the Total Load and Divide by the Circuit Rating. Example: 10 amps Load / 15 amp Circuit Rating = a 66% Load.
- Locating the Power Source
- All of these wires are already located at the existing light fixture, so the easiest method for adding one or more light fixtures is to extend the wiring from the existing light fixture to the new location of the additional light fixture.
- It is best not to install the wiring from the wall switch, in fact the wall switch may not have the necessary neutral wire, and in that situation the wiring would to be correct due to the absence of the neutral wire.
- It is easy to get confused about switch wiring when white wires are seen attached to a switch, however a white wire on a switch is the continuation of the loop of wire that is used for the switching process, this is also known as a switched leg.
- Making the Electrical Wiring Connections
- Wiring connections are made by stripping off about 1 inch of the outer wire insulation from each wire to be spliced together.
- Typical wiring connections are made color to color, such as black to black, white to white, and bare copper to bare copper or in some cases green and the bare copper are used as the ground wires.
- Wire connectors that are sized for the size of the wires and the number of wires to be connected. Commonly yellow or red wire connectors are used for wire splices for 15 gauge and 20 gauge wire respectively.
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