Based on the product that you have selected, you may need a neutral or earth ground. If you are installing Decora Smart Wi-Fi, Z-Wave, or Zigbee see the article How do I know if I have a Neutral? If you are installing Decora Smart No-Neutral Switch (DN15S) or Dimmer (DN6HD), you will need an earth ground.
Grounds in electrical boxes started in the 1960s. If your home was built in the 1970s or later, it is highly likely your electrical boxes include a ground. For older homes with plastic electrical boxes, the ground can be determined with a visual inspection. If the boxes are metal, a simple electrical test with a voltmeter can confirm if the box is grounded.
To determine if you have an Earth Ground, you must first disable the live circuit from your electrical junction box to your switch.
- For the load you are verifying - start with the light on, and switch the circuit breaker or pull the fuse to ensure the load turns off.
- DO NOT disconnect any wires.
- Note, just because the load is off, it is possible to have more than one live circuit in the box. Be certain power is removed to any adjoining loads in box.
- With power to the box turned off, unscrew and remove the wall plate and existing switch.
Use the following as a guideline to determine if you have an Earth Ground. Installation should be performed by a professional electrician, not all structures are wired the same; therefore, results may be different than described below.
Power is delivered to the switch box or load over 3 conductors:
- Black – Hot
- White – Neutral
- Bare copper – Earth ground
If you have a plastic box:
- With the power off, look for bare copper conductors
- The bare copper may be the same thickness (gauge) as the white or black conductors or it may be much thinner
- The bare copper will typically be attached to the grounding screw or terminal on the switch
- If there are multiple electrical connections or switches in the box, it is common for all of the bare ground wires to be tied together
- If a modern electrical device is installed, it may have a green lead attached to the bare copper
- To confirm a ground wire is properly connected to ground (i.e. grounded)
- With the power off, separate the wires in the box and ensure that no conductors are touching
- Restore power
- With a voltmeter, set the meter to read AC voltage in the 120 VAC range
- Carefully touch one probe to the bare copper conductor and the other probe to the white conductor and then to the black conductor while observing the voltage reading
- If you see a reading of approximately 120VAC when touching the white or the black conductor, then that conductor is the hot and the bare copper conductor is grounded
- If the reading is much lower than 120VAC on both the white and black conductors, then the bare copper conductor is not grounded
- If the bare copper conductor is not grounded, it will need to be grounded by an electrician in order to use a Decora Smart No-Neutral Switch (DN15S) or Dimmer (DN6HD)
- Be certain to turn power back off before completing the installation
- If no bare copper connection exists in the box, then a ground connection would need to be added by an electrician in order to use a Decora Smart No-Neutral Switch (DN15S) or Dimmer (DN6HD)
- If the box has a neutral a Decora Smart Wi-Fi Switch (D215S) or Dimmer (D26HD) can be installed
If you have a metal box:
- With the power off, look for bare copper conductors
- The bare copper may be the same thickness (gauge) as the white or black conductors or it may be much thinner
- The bare copper will typically be attached to the grounding screw or terminal on the switch
- If there are multiple electrical connections or switches in the box, it is common for all of the bare ground wires to be tied together and connected to the electrical box screw
- If a modern electrical device is installed, it may have a green lead attached to the bare copper
- If no bare copper connection exists in the box, it is possible the box is grounded via BX cable
- With the power off, separate the wires in the box and ensure that no conductors are touching
- Restore power
- With a voltmeter, set the meter to read AC voltage in the 120 VAC range
- Carefully touch one probe to the box and the other probe to the white conductor and then to the black conductor while observing the voltage reading
- If you see a reading of approximately 120VAC when touching the white or the black conductor, then that conductor is the hot and the electrical box screw can be used as a ground
- If the reading is much lower than 120VAC on both the white and black conductors, then the box is not grounded
- Be certain to turn power back off before completing the installation
- If the Earth Ground connection does not exist in the box, then a ground connection would need to be added by an electrician in order to use a Decora Smart No-Neutral Switch (DN15S) or Dimmer (DN6HD)
- If the box has a neutral a Decora Smart Wi-Fi Switch (D215S) or Dimmer (D26HD) can be installed