In the United States, grounding of appliances is governed by the National Electrical Code (NEC), which is updated regularly by the National Fire Protection Association (NFPA). The primary purpose of grounding is to provide an extra layer of safety by directing electrical faults away from the user and into the ground, reducing the risk of electric shock and potential fires.
The general rule for grounding appliances in the United States is that all appliances that have metal enclosures or can conduct electricity should be grounded. Grounding is typically achieved by connecting the metal components of the appliance to the ground wire of the electrical system. This ground wire is usually a bare or green wire in the electrical circuit.
Some common appliances that should be grounded include washing machines, refrigerators, ovens, dryers, dishwashers, and power tools, among others. These appliances often have metal exteriors or components that could become energized in the event of an electrical fault.
However, there are certain types of appliances that are exempt from the grounding requirement. These include:
Appliances with Double Insulation: Some appliances are designed with double insulation, meaning they have two layers of insulating material to protect users from electrical shock. These appliances are labeled with the symbol "Double Insulated" or "Class II" (a square inside another square) and do not require grounding because the extra insulation provides adequate protection.
Small Appliances: Small appliances with two-prong plugs (non-polarized plugs) are often exempt from grounding. These appliances, like blenders, toasters, and some lamps, typically have plastic enclosures and are considered low-risk for electrical shock.
Certain Old Appliances: Older appliances designed before grounding requirements were established might not have a grounding provision. In such cases, it's generally recommended to replace or update these appliances to meet current safety standards.
It's important to note that while some appliances may be exempt from grounding requirements, they still need to comply with other safety standards and regulations to ensure safe operation. If you're unsure about the grounding requirements for a specific appliance, it's best to consult the manufacturer's instructions or seek advice from a licensed electrician. Additionally, local building codes might have specific requirements that could be more stringent than the NEC, so it's essential to be aware of those as well.