A new bathroom fan I want to install has 2 green and 1 each white and black. The line in the attic consists of a white, a black and a ground. What do I do with the 2 green wires?

  • 4
    All green wires are grounds. Ground is bare, yellow/green or green. That's the one wire standard the whole world agreed on! Jan 31, 2021 at 18:40
  • @Harper-ReinstateMonica: I used a system that used green for Common. The system had no ground per say, but Common was the thing everything connected to. The whole thing floated with respect to building ground due to transformer decoupling.
    – Joshua
    Feb 1, 2021 at 3:16

2 Answers 2


Green designates a ground (earth) wire. If the incoming wires have a ground wire (usually bare copper or green stranded insulated) attach the grounds to it with a wire nut or a crimp connector.


In Alternating current (AC) electrical distribution, that is used in providing electricity to light fixtures, switches and outlets in buildings, the ground wires are bare copper. Since it does not carry and load, electricity, it has no need for an insulating cover. When the ground wire enters a fixture box or outlet box it is tied together with other ground wires that are/may be entering the box.

All of the ground wires in the system are connected back at the main breaker box which is connected to the earth (grounded) via a grounding rod. This creates a ground through out the whole system.

If the fixture box is metal then the bare ground wires are usually attached to the box thereby grounding the box to the system, or if the box is plastic they are tied together with a crimp or a wire nut or just twisted very tightly together with linesman pliers.

What do i do with 2 green wires

In fixtures and devices Green insulation is used on wires as the designated color to indicate that it is a ground wire. When installing a light fixture you need to connect the Green wire(s) of the fixture to the ground wires in the box. This can be done with a wire nut or, if it is a metal box that is grounded, with a screw to the body of the box.

All fixtures, switches and outlet receptacles are required to be grounded. (connected to the ground system)

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