Information about the types of failures we find 

This series is designed to pass on  some of what we have learned from doing Electrical Safety Testing over several years. The information is probably not available elsewhere as is is presented from our particular perspective as safety testers. It is not intended to cover all aspects of the safe use of electrical products, only to highlight issues we have become aware of through safety testing. As such, it should be read in conjunction with and in addition to warnings and recommendations from the manufacturers, regulatory bodies and electrical authorities. 

AC Adaptors - Care and feeding of

AC adaptors are so familiar that they tend to be overlooked as a potential hazard. Some people who should know better, will even tell you that AC adaptors don't need to be checked. The news for these guys is all bad. 

The Australian Standards do not exclude AC adaptors from testing. While an adaptor in good condition is very unlikely to fail an insulation test, we find a significant number of adaptors fail for other reasons.  Their failure rate ( the number of failures per units tested) can be similar to the rate for supply leads.  

Further, faulty adaptors are just as likely to present an immediately lethal hazard. Typically the plastic case fails by cracking, disintegrating or separation of a join. With the outer case gone, 240 volt contacts are often exposed.   

Contributing factors

Factors contributing to failures appear to be:

Impacts from being dropped, heat, stressing of the AC pins and old age. The last item is inevitable but the others can be avoided. 

If an adaptor gets dropped it should be carefully checked for cracks and loose pins etc before being reused.

They usually run warm but shouldn't be overly hot to touch. Some normally run warmer than others and these (in particular) should have as much cool air flow as possible. That is, not be run in a confined space.

We sometimes find adaptors running hot because they are supplying the wrong load. If using a substitute adaptor, its specifications should match the voltage AND current of the load. (Email us if you want to know more about this.) If the specification label is missing from an adaptor and you aren't sure what it was for,  it shouldn't be used. 

Stressing of the AC pins is usually caused by the adaptor being jammed up against something in the next outlet. (This probably doesn't do much for the outlet either.) We know it is a problem because cracks have been seen developing around the AC pins of these adaptors. The simple solution is to use a power board to plug into the outlet and plug the adaptor into the power board. 

In summary, AC adaptors have the potential to cause fatality. They should be included in your EST program and handled with respect.