how to change a ballast

How to Replace Ballasts

Ballast Wire Colors

If a ballast is replaced with the exact same type of ballast, the wire colors usually match. If an old T12 lamp magnetic ballast is replaced with a newer T8 lamp and electronic ballast, the colors will probably not match. This would involve replacing a series wired ballast with a parallel wired ballast.

When replacing a ballast where the wires colors don't match, it is important to understand the ballast wiring concept. Just matching colors could cause a problem.

Ballast wire (top) is 18 AWG. Line voltage wire (bottom) is 12 AWG.

Strip wires about 3/8 to ½ inch in length.

Use orange, yellow, or tan wire connector.

Ballast wires are 18 AWG. Use a blue wire connector for up to four 18 AWG wire connections.

Use orange wire connector for more than four 18 AWG wire connections.

Wire connector for line voltage wires Wire connector for ballast to lamp holder connections

Light fixtures from the factory are wired with the ballast wires connected directly to the lampholders. When changing a ballast, it is not feasible to disconnect and reconnect the wires from each lampholder. When done this way, the lampholders need to be removed from the fixture. It is simpler and faster to do the following:

1. Shut off power to light fixture at the circuit breaker.

2. Cut the wires close to the old ballast and remove the ballast.

3. The wires from the new ballast are trimmed of excess length.

4. The new ballast and lampholder wire ends are stripped.

5. The new ballast wires are connected to the lampholder wires with wire connectors.

Ballast Wire Connectors

Twist-on wire connectors are also know as wire nuts. Wire-Nut® is a registered trademark of Ideal Industries and is the name of their commonly used twist-on wire connectors. Wire nuts come in different sizes depending on wire gauges and number of wires that are to be connected together. See Wire Connector page for more info.

Wire connector for line voltage wires

Wire connector for ballast to lamp holder connections