Why was the ground for this fluorescent fixture not connected to the ballast?

Question

I just purchased a set of fluorescent fixtures that are fitted with a plug to connect to a standard 3-prong receptacle. My intention is to replace the plug with Romex cable, and wire the fixture directly into a switched-controlled circuit.

When I disassembled the fixture I noticed the plug's ground wire was attached to the fixture chassis via a screw, while the live and neutral attached to the ballast. However, the ballast has a terminal for live, neutral, and ground wires (see photo), which is confusing. Why not just attach the all plug wires directly to the ballast?

I suspect this happened because the plug ground wire is stranded and that it may not make good contact with the spring-loaded terminals on the ballast. In any case, is my plan to connect the three Romex wires directly to the ballast sound?

Answer 1

My guess would be that because the fixture has a metal frame, the ballast is grounded via its contact with frame. If the frame were plastic, you would need to use the terminal on the ballast.

If you're converting it to hardwired, you should definitely connect the ground wire to the grounding screw.

You're also going to need to cut a hole if there's no punch-out available and make sure to use a cable clamp/strain relief suitable for using with romex.

Answer 2

Look for the Pal nut on the other end holding the ballast to the metal housing it's mounted on. It's made to bite through the paint to ground the ballast to the housing which is then grounded.

For safety, it's more important that the metal housing you will touch be solidly grounded than the ballast which is inside and protected from direct contact be grounded and then hope that the fastening between it and the housing provide low enough resistance to ground the metal you will touch in operation.

Sometimes that which "makes sense" is backwards to what you're really trying to accomplish.