Class II Double Insulated Equipment
Most lightweight portable equipment, including power tools, hairdryers, electric razors, power supplies for cell phones etc fall in to this category. The words ‘Double Insulated’ or the symbol should be displayed on the nameplate.
All class II double insulated equipment do not need an earth conductor and should not be earthed (note: appliances still may have an earth pin on the plug for extra mechanical support) – the primary safety protection for the operator is the fact that the appliance has two layers of insulation hence the name ‘double insulated’. It is essential therefore that there is no damage to the insulation such as cracks etc. You will be aware of many generic items that are class II but when it comes to the AS/NZS3551, you will more likely be testing class II items such as beds, pumps and chargers found on equipment like wheelchairs and hoists. There may be other items but these are the most common you will probably deal with and we will demonstrate how to test several of these later in the course
Class II equipment does not need to have an earth pin on the plug but may still have one. The pin is often left in place as it acts as a mechanical securing device which prevents the plug from becoming easily unplugged.
You should be aware of the above symbols but practically speaking the only one that you will really come across and put into practice identifying is the BF symbol. You can see one in the workplace environment below located on a medical pump.
The above symbols are put on by the manufacturer to describe the type of medical equipment the appliance is and what medical rating the testing should be done for testing the appliance. For you, as the trainee, you will only be dealing with appliances that are type B and type BF. An example can be seen below.
