What Are The Red And Blue Wires On A Ballast

An electronically controlled device known as a ballast delivers and controls electricity to fluorescent lights. According to Electrical 101, the ballast is located within an overhead fluorescent bulb unit and is usually concealed from sight by a cover or plate. It is necessary to repair a worn-out ballast since it may result in hazardous shorts or electrical spikes. Additionally, it may result in fluorescent bulbs burning out too soon.

What Are The Red And Blue Wires On A Ballast

There are several different kinds of ballasts, but two-tube light fixtures typically use the basic kind. The ballast contains a hot as well as neutral wire for receiving energy, two blue wires, and a red cable for feeding electricity to the lighting at the other end. We’ll talk about this topic in more detail and learn more about ballasts and the wires that make them up in this piece.

The Ballast’s Red and Blue Wires

A mechanism used in series with a load to restrict the flow of electricity in an electrical system is known as ballast. The inductive ballast used in CFLs is a well-known and often-used example. Without it, the energy thru the tubes would’ve been allowed to increase to a damaging level because of the negative differential resistance of the tube’s voltage-current feature.

Ballasts come in a wide range of complications. They might be as basic as a resistor, inductor, or capacitor linked in series with light, or as sophisticated as the electrical ballasts used in higher flow lamps (HIDLs) and compact fluorescent lights (CFLs) (HID lamps).

The wiring diagrams on the internet on the replacement ballast will show you whichever color-coded wires go where in the light fixture, so pay close attention to it. Five wires are provided by the new ballast: black, white, blue, blue (equivalent), and red. A hot plus neutral wire and two blue wires and a red wire are located at one end of the ballast, which is used to deliver electricity to the lights.

Kinds of Ballast and All There is to Know

In this section, we’ll talk about different types of ballasts, how to wire them, test them, and other important ballast wiring-related topics.

Ballasts: Magnetic vs Electronic

The majority of quick start, older magnetic fluorescent ballasts are series connected. Instant start (connected in parallel), quick start (wired in series), programmed start (wired in series-parallel), dimmable, and CFL ballasts are examples of more recent electronic ballasts.

Ballasts With A Rapid vs An Instant Start

When one of the lights in a quick start ballast (which is wired in series) fails, the connection is opened, and the remaining lamps won’t ignite.

The lights function independently of one another when a circuit’s numerous lamps are wired in parallel with an immediate start ballast. The others can continue to run as long as the circuit connecting them to the ballast is intact, even if one light fails. If one light in a series-parallel-wired 3- or 4-lamp controlled start ballast malfunctions, the lamp(s) in the parallel connection will keep running.

Only series wiring is possible for rapid-start ballasts. Following the wiring schematic on the ballast, quick-start ballasts can only be connected in parallel. A fluorescent fixture’s wire must be switched from series to parallel to go from quick start to instant start.

Grounding A Ballast

A ballast must always be grounded. If the lighting fixture is grounded correctly, grounding normally happens automatically.

A light fixture has to be linked to the power source’s ground line. Automatic grounding of the ballast occurs when the ballast is attached to a metal light fixture. A ground wire has to be attached to any ground terminals found on ballasts.

The Wiring Of A Ballast

With a wire connector, join the black and white cables coming from the home circuit wire to the black and white wires coming from the ballast. On the ballast, there ought to be a combination of red and blue wires. If necessary, remove 1/2 inch of insulating from the end of the wires.

Testing For Fluorescent Ballasts

Set the resistance settings on the multimeter to somewhere about 1,000 ohms to test it. The white ground cable on the ballast should be connected to the black leads. After that, use the red lead to test each additional wire. A proper ballast will give you an “open-loop” or maximum resistance when you perform this test.

What A Fluorescent Light Fixture’s Ballast Does

The ballast controls the current to the bulbs in a fluorescent system and supplies enough voltage to turn them on. A fluorescent light directly attached to a high-voltage electricity supply will rapidly and uncontrollably increase its power usage without ballast to regulate it.

Size Of The Wire For The Ballast

The following recommendations should indeed be considered for installations wherein ballasts should be installed distant from light sockets utilizing extended wire leads: Use #14 wire size for lengths up to 15 feet. Use #12 wire size for lengths up to 25 feet.

What do the common and individual cables on fluorescent ballasts do?

Each of the bulb holders on the opposite side of the tubes is connected by the same wire(s). Based on the kind, brand, and quantity of lights a fluorescent ballast can support, different wire colors will be used for the individual and common connectors.

Frequently Asked Questions

What Kind Of Wire In A 30-Watt Ballast Is It Wired With?

The red wire is shared by both lamps when wiring two 30W bulbs, thus need to utilize the other blue wire to supply electricity to that light. Just wire the new ballast according to the wire color codes in the figure above. The light would be flawless.

What Do Fluorescent Lighting Fixtures’ Magnetic Ballasts Do?

A magnetic ballast was used in older fluorescent lighting bulbs to regulate the flow of the black and white cables that the ballast is connected to should have their wire nuts removed. 47CFR Part 18 Non-Consumer of the FCC.

What Is The Purpose Of The Red Wire On A Ballast?

On the opposite side of every lighting, the common red wire links the ballast to both bulb holders. The two common side light holders are connected by an extra red wire.

Which Wire On A Ballast Is Hot?

Black is hot when wiring a 120v AC circuit, presuming you’re in the US. Red is a close second. Green is the ground; white is neutral. 

What Occurs If A Ballast Is Improperly Wired?

A failed ballast must be changed since it might result in short, burnt-out tubes or possibly a fire. Lack of illumination, blackened ends on fluorescent tubes, and brown, burned tube electrodes are all signs of a defective ballast.


A fluorescent light hooked up to a high-voltage power supply could rapidly and uncontrollably increase its current consumption without ballast to regulate it. We believe you now own all the knowledge you want concerning ballast. If you replace your ballast as required, you’ll save money and protect your health.

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