Just curious about electrical safety at home.

When is the last time you exercised the "Push to Test" button on the GFCI device in you HOME? This may be called something different outside of the United States and Canada such as Earth Leakage Circuit Breaker or Residual Current Device.

This week
This month
This year
A long, long, long time ago...
Um.... never
I Don't have these devices

I have 9 GFCI devices around my house. They do not all get checked each and every month.

As a general topic, ground fault detection and/or tripping is very regionalized as well as industry specific. It is relatively uncommon outside of petrochemical/mining in the U.S., for instance but in some countries and industries it is required. As an example in the U.S., MSHA Part 77 requires it for all coal mines and all voltage levels. In Canada M421 requires it for all mines, not just with specific minerals. Similarly where ungrounded systems are used, it is Code required to have ground fault detection (alarm only). It is also "required" for construction sites as per OSHA regulation in the U.S. but up until recently, the price of a portable GFCI was so crazy that they were rarely on the job site but more and more these days as the prices came down, I'm starting to see them used everywhere.

What is much more rare is when someone actually tests them. Many of the portable ones though enforce this because they contain an undervoltage trip function so at least the trip function (if not the actual detection function) gets tested every time it gets unplugged.

I've found any number of GFCI's manufactured as receptacles that fail around the 10 year mark in residential installations, almost to the point where if they are that old, I automatically replace them.

I should know better but realized I have not checked this in a very long time. Thanks for a great reminder (whether that was the intention or not) I just checked it a few minutes ago.

The year matters, approx five years ago the UL standard changed. The UL standard is changing again this June 29th. Prior to these changes the devices were dumb. The first change forced the receptacle open if the the push-to-test saw a problem with the electronics or tripping mechanism, the older style merely created a current unbalance in the differential trip circuit. The latest change requires the receptacle to periodically self test the electronics.

Whether it self-tests or not, the trip mechanism itself can and does still fail to trip. Seen that case, too. Some of the older "test" buttons didn't even introduce an imbalance...they were really just testing the mechanism.

With breakers the two most common failure components according to IEEE Gold book data are the mechanical mechanism that opens the power conductors, and the trip relay, although this does not necessarily translate 100% to small residential GFCI's. The mechanical failures are primarily due to lubrication issues (too much, too little, seized up, etc.) but I've also seen misalignments, worn parts, etc. The trip relay as with all electronic parts fails mostly because of failed solder joints. Adding more and more complexity (as in the revised UL Code) only makes matters worse in this regard. The expectation would be that reliability should increase as a result of more "coverage" on self tests. But in fact quite often what happens is just the opposite as system complexity increases.

Yes Paul, the principle is true not only for RCDs (GFCIs) but circuit breakers in general. Even with the best of lubricants (and take care that the correct lubricants are used - bad experience with some service experts flushing out lubricant with penetrating oil) stiction can cause circuit breakers of all types to fail to trip (HV & LV). Exercising of the breaker at least annually is normally recommended to overcome this issue. Generally working the mechanism a few times can restore the circuit breaker opening time quite quickly. The danger is that with routinely tested CBs, where the failure mode is consequently eliminated, it could be concluded that the test frequency is too high. Stick with proven experience.