How to Wire an HPS Ballast

outdoor street light
  • 3-5 hours
  • Intermediate
  • 200-400
What You'll Need
HPS ballast kit
Wire strippers
Wire nuts

When installing an HPS ballast, it is probably more economical to buy the parts unassembled. However, there are also ready-made kits that are designed to be installed with ease. Unassembled or in kits, follow the steps below to effectively install your HPS ballast.

Step 1 - Prepare

There are three basic parts inside the ballast: the transformer, the capacitor, and the ignitor. Each of these parts can be bought separately. When purchasing individually, make sure to buy the correct rating for the home, usually 120V in most homes. In addition to these three, the HPS ballast should also be wired to a bulb and socket; therefore, there is a need for a 14 gauge wire, wire nuts, power cord, and male plug set. Also, obtain a wiring diagram for the ballast. This usually comes in the manual or written on the ballast enclosure.

Step 2 - Wire the Internal Parts

The wiring diagram shows three components connected to the lamp (the transformer, the capacitor, and the ignitor). Inspect the two sides on the transformer to see its long side and the short side. Notice that wires come out of the device through two protuberances.

The capacitor has two wires and the ignitor has three wires (X1, X2, and X3). Keep in mind that the description on the wires is important when connecting them.

Locate the wire on the transformer with the word cap. Connect this wire to the capacitor and secure the connection with a wire nut. On the long side of the transformer, locate the wire marked X3 or 3. Connect this wire to the ignitor wire marked X3 or 3 as well. Be certain no bare wire is exposed.

Step 3 - Connect the Ballast to the Socket and Lamp

a bundle of multi-color wires

To connect the ballast to the socket, get the white wire from the socket, locate the com2 or comX2 on both the short side of the transformer and the igniter and connect the three together using a wire nut.

Locate the wire labeled lamp on the long side of the transformer and the X1 wire on the ignitor. Connect both of these together with the black wire coming from the socket. Connect all three using a wire nut.

Step 4 - Final Connections

There should be two wires coming out of the transformer’s short side labeled com and 120. Remove the sheathing from the power cord, and strip the insulation on both black and white wires about ½-inch. Connect the com wire to the white wire on the power cord and the 120 wire to the black wire. Make sure all connections are secured using wire nuts. Afterwards, connect the bare wire to the base of the transformer or to the enclosure. Install the enclosure to cover the ballast and tighten the screws.

Step 5 - Test

Check to make sure that all connections are correct and complete. Install a bulb onto the socket and plug the ballast to a power supply. If the light works, the wiring is successful.