How to identify the positive and negative wires on a lamp
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Whether you use a fluorescent, chandelier, or incandescent light, you may need to replace or repair them from time to time. One of the most important parts of this job is knowing the differences in wiring. Most lighting fixtures have a hot wire and a neutral wire. Sometimes you will also see a ground wire. For proper wiring, identifying these wires is critical. With that in mind, here are some tips on how to tell the difference between the positive and negative wires on a lighting fixture.
Typically, in an AC lighting circuit, the white wire is neutral and the black wire is hot. The green wire is the ground wire. However, some lighting fixtures may have two black wires and one green wire. The black wire with white stripe or fins is the neutral wire.
Facts about luminaire wiring
Most fixtures are wired the same way. They are connected to each other in a parallel circuit. These fixtures have three wires; hot wire, neutral wire and ground wire. However, some connections do not have ground wires.
AC powered luminaires
AC powered lamps come with three different wires. The hot wire is the live wire, and the neutral wire plays the role of the return path. The ground wire does not carry current under normal conditions. It passes current only during earth faults.
Tip: Grounding is a mandatory safety mechanism for your lighting fixtures.
DC powered luminaires
When it comes to DC powered lamps, wiring is a bit different from AC wiring. These circuits have a positive wire and a negative wire. Here the red wire is positive and the black wire is negative.
4 step guide to disassemble the fixture and identify the positive and negative wires
Things You'll Need
- Screwdriver
- tester
- multimeter
- Wire stripper (optional)
Step 1 - Power off the light
Turn off the lights first. Find the circuit breaker that powers the lights and turn it off. (1)
Step 2 - Remove the outer casing
Then locate the screws holding the outer body of the lamp. Depending on the type of luminaire, this process may vary. If you are using a chandelier, you may need to remove three or four screws.
The same goes for fluorescent lamps. The purpose of this step is to find the wires.
So, remove all obstacles that may hide the wires.
Step 3 - Pull out the wires
After removing the outer casing, you can inspect the wires. For better observation and verification, pull them out.
Step 4 - Correctly identify the wires
You are now ready to identify the wires. Follow these guidelines properly.
Identification of hot and ground wires
There should be three wires. The black wire is the hot wire. Most fixtures have black wires. Remember that the wire should just be black. There will be no markings on the wires, except for information about the wire (sometimes there will be none).
The green wire is the ground wire. In some cases, there will be no colors for the ground wire. For example, some manufacturers use bare copper wires for grounding. (2)
Determine the neutral wire
Determining the neutral wire is a little tricky. In most cases, the neutral wire is white. However, some fixtures come with two black wires. When this happens, there are two ways to identify the neutral wire.
Method 1 - White Stripe or Ribbed Edge
If you can find a black wire with a white stripe or ribs on the surface, it is a neutral wire. The other wire is the black hot wire.
Method 2 - Use a tester
Use a tester if you can't find the stripe or rib on those black wires. When you place the tester on the hot wire, the tester should light up. On the other hand, the neutral wire will not turn on the tester indicator. Be sure to turn on the circuit breaker at this stage and strip the wires if necessary.
Keep in mind: Using a tester is a great option for all of the above situations. Even if you can correctly identify the wires, check them with a tester again to make sure everything is in order.
Take a look at some of our articles below.
- How to distinguish a negative wire from a positive one
- What is the wire size for the lamp
- How to install a neutral wire
Recommendations
(1) supplies power - https://www.sciencedirect.com/topics/
engineering/power supply
(2) copper - https://www.britannica.com/science/copper
