One of the first things to work out before testing an appliance is whether it's Class I or Class II.
Why? Because the classification affects the electrical safety tests that need to be carried out.
There are a few clues that can help you identify the class, but don't rely on whether an appliance is metal or plastic, or simply how many pins its plug has.
Check the Manufacturer's Label First
In this short video, Mark, one of our test and tag trainers, shows you where to find the manufacturer's label or rating plate and what to look for when identifying Class I and Class II equipment.
For Class II equipment, one of the key things to look for is the square-within-a-square symbol. This indicates that the equipment uses double insulation and doesn't rely on protective earthing for its electrical safety.
What Is Class I Equipment?
Class I equipment relies on protective earthing as part of its protection against electric shock.
It typically has an earth connection, and may have a metal enclosure or a three-core cable. However, these features alone aren't enough to determine its classification.
Common examples can include desktop computers, kettles, microwaves and fridges, depending on the design and construction of the appliance.
Always check the manufacturer's label, markings and equipment information rather than relying on appearance alone.
What Is Class II Equipment?
Class II equipment uses double or reinforced insulation to protect against electric shock. It doesn't rely on protective earthing and is commonly identified by the square-within-a-square symbol.
Examples can include hair dryers, chargers, some power drills and other household appliances, depending on their design.
Remember, a plastic enclosure doesn't automatically mean an appliance is Class II. Always check the relevant markings and manufacturer information.
Class I vs Class II at a Glance
| Class I | Class II | |
| Protective earth | Relies on protective earthing | Does not rely on protective earthing |
| Protection | Insulation and protective earthing | Double or reinforced insulation |
| What to look for | Equipment markings, construction and earth connection | Square-within-a-square symbol |
Why Getting the Class Right Matters
Correctly identifying whether equipment is Class I or Class II helps you determine which electrical safety tests are appropriate. However, before you test anything, a visual inspection is required to ensure there's no visible damage or defects.
If you're learning to test and tag, identifying equipment classes is one of the fundamentals you'll cover during the practical part of your test and tag training course, using real appliances and portable appliance testers.
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