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Testing and Standards

IEC 61140 – Safety Classes Description

The Quality Control Blog recently discussed the safety classes of IEC 61140. The last article showed why it matters and how to ensure compliance. Three safety classes are important nowadays. Lets talk about how we can spot physical non-compliance. These are very common for products made-in-Asia. Suppliers sometimes are unaware of the regulation. Other manufacturers simply try to cut corners.

Safety Classes: Class I

Safety Class I

This appliance class is designed for high voltage devices. An inspector will check for proper grounding wires in the cable, connector and device. The inspector will also check if there is a fuse, circuit breaker or residual current device. During on-site tests, an inspection company will also apply very high currents to test the insulation and fuse. A typical example is a fridge – and yes, some factories try to pass off Class II (designed for lower voltage) on a fridge!  

Safety Classes: Class II

Safety Class II

Designed for medium/low voltage appliances, an inspector will check for double insulation. A grounding wire is not necessary. We recently heard of an inspection of hair straighteners with single insulation cables! In this case, replacing the cables delayed shipment substantially.

Safety Classes: Class III

Safety Class III

Products designed for low voltage devices (below 50 V alternative current or below 120 V DC) require  simpler cables. Examples include flash lights or your loudspeakers. What many Chinese manufacturers fail to realize, is that Class III never applies to medical devices.

Remember: you can always use a higher Safety Class but never a lower one. Also, it is best to avoid mixing components from different classes (this is the most common problem).


Maximilian Hess

I am in the customer service team, based in China. I also work on marketing projects. I am a technical and precise person. I enjoy writing about my daily life at work, telling about the problems faced and the solutions!

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