Walk any commercial site with a PAT engineer and the first thing they do with each appliance is identify its class. That single call, Class 1, Class 2 or Class 3, decides which electrical tests get carried out and which ones do not. Get the classification wrong and the wrong tests run, the wrong results go on the report, and the whole exercise loses its value. If you are the person signing off electrical equipment testing across an office block, warehouse or multi-site portfolio, understanding what each class actually means puts you in a much stronger position when reviewing your PAT testing results.
What is Class 1, Class 2 and Class 3 Appliances?
Every portable electrical appliance falls into one of three classes based on how it protects the user from electric shock.
Class 1 appliances rely on an earth connection for protection. The appliance has a metal casing connected to the earth pin in the plug, so if a live wire comes loose inside, the current flows safely to earth rather than through anyone touching it. You will find Class 1 equipment across almost every commercial site.
Class 2 appliances are double insulated. They do not rely on an earth connection because the insulation around the live parts is built in two layers. If the first layer fails, the second layer still protects the user. These are marked with a small double-square symbol on the rating plate.
Class 3 appliances run on Separated Extra-Low Voltage (SELV), typically supplied through an isolating transformer or a dedicated power supply unit. Because the voltage is so low, the risk of electric shock is minimal. The appliance itself does not usually go through the standard PAT testing procedure, but the power supply that feeds it does.
How to Tell What Class Your Appliances Are
On a busy commercial site, the quickest way to identify class is a combination of the rating plate, the plug and the appliance markings.
Class 1 appliances rely on an earth connection for protection. Common examples across offices and industrial premises include kettles, washing machines, microwaves, desktop PCs, and floor-standing fans.
Class 2 appliances carry the double-square symbol (a smaller square inside a larger one) on the rating plate or casing. They have no earth connection. You will typically see these on TVs, hairdryers, desktop printers, small kitchen appliances such as toasters and food mixers, and power tools with plastic casings.
Class 3 appliances operate at Separated Extra-Low Voltage (SELV) and are powered through an external transformer or power supply. Examples include phone chargers, laptop power supplies, and low-voltage LED lighting strips. Class 3 equipment still needs to be subject to a formal inspection process. In practice, the transformer or power supply unit that feeds the appliance is what gets classified and tested as part of the PAT testing procedure, and the Class 3 appliance itself is inspected as part of the visual examination.
If you are unsure about any appliance on your site, your engineer will identify the class on arrival as part of the visual examination before any electrical tests begin.
How Each Appliance Class Is PAT Tested
The class of an appliance directly determines which electrical tests are carried out.
For Class 1 appliances, the engineer starts with a visual examination of the casing, cable, plug, and fuse. From there, the electrical tests include an earth continuity check, plus insulation resistance and polarity checks where applicable, up to three tests depending on the construction of the appliance. Because Class 1 relies on that earth connection, verifying it is intact is the priority.
For Class 2 appliances, there is no earth connection to test. The visual examination still covers the casing, cable, plug, and fuse, but the electrical testing focuses on insulation resistance. That double layer of insulation is the appliance’s only line of defence, so confirming it is in good condition is what matters most.
For Class 3 appliances, the appliance itself sits outside standard PAT testing. The power supply or transformer that feeds it is what gets tested, and it will be classified as either Class 1 or Class 2 depending on its own construction. If the transformer is earthed, it gets Class 1 tests. If it is double insulated, it gets Class 2 tests.
Our engineers identify class on arrival and carry out the right tests for each item. You do not need to pre-sort or label anything beforehand. Once testing is complete, you receive a certificate and an itemised report covering every appliance tested, with pass and fail outcomes recorded against each one. Passed items are labelled with the date tested, and any items that fail are labelled with the reason and removed from use where practicable.
You can find a full breakdown of the PAT testing procedure, including the visual examination and electrical tests, in our guide to PAT testing.
Does Appliance Class Affect PAT Testing Frequency?
This is one of the most common misconceptions. It used to be the case that the class of an appliance determined how often it was tested. Class 1 items might have been on a shorter cycle than Class 2, for example.
That changed with the 5th Edition of the IET Code of Practice for In-Service Inspection and Testing of Electrical Equipment. The industry moved to a risk assessment approach, and frequency is now based on four factors:
- How often the equipment is used
- The environment it is used in
- Who uses it
- The lifespan of the equipment
So, a Class 1 kettle in a low-traffic office kitchen and a Class 1 industrial grinder on a factory floor would not automatically sit on the same testing cycle, even though they share the same class. The risk profile of each appliance is what drives the schedule, not the class alone.
If you are not sure what needs PAT testing on your site or how often, we can advise based on your specific setup.
Book Your PAT Testing with Hawkesworth
We take care of appliance classification on the day. Our 200+ City and Guilds certified, DBS-checked engineers identify the class of every item on arrival and carry out the correct tests accordingly, with out-of-hours and weekend testing available at no extra charge.
Whether you manage a single office or a portfolio of commercial sites across the UK and Ireland, a company like Hawkesworth can do all the hard work for you. Request a quote and we will get back to you.
Michael Kiddle
Managing Director of Hawkesworth and a nationally recognised leader in electrical and fire safety, Michael (GIFireE) directs one of the UK's leading compliance companies, safeguarding thousands of businesses each year. Through his voluntary Safe Home Initiative, he has identified and removed thousands of dangerous household appliances from vulnerable people's homes, replacing each one with a safe alternative free of charge.
