Opening a failed outlet strip reveals something really scary.
This photograph shows what was left of a GE SurgePro outlet strip that failed catastrophically.
Failed outlet strip
When this happened, the circuit breaker in the basement shut off but, quite clearly, there were some very dangerous pyrotechnics going on until that basement circuit breaker finally responded.
When I opened the plastic shell and took out a circuit board, I discovered something really scary.
The failure point
I didn't trace out the exact circuit, but there were three varistors, one of which had clearly been blasted and next to that varistor, there was a charred fuse with one broken wire lead. The scary part was that one lead of the fuse's package had broken open. The charred fuse itself had NOT blown out.
Using an ohmmeter, I found that the fuse itself still had continuity. One wire of the fuse's package had unintendedly opened up and that is NOT how fuses are supposed to work.
Taking a look at the bottom of the plastic case, I found the following:
Outlet strip label
Even though there is a label to the effect that this product was UL Listed, its pyrotechnic failure raised some very serious questions in my mind. I decided to do a Google search for the model number and this is what I found:
There were a great many search results, but this one in particular from Amazon caught my attention with that warning that "surge protectors wear out over time."
Is wearing out what killed the varistor and if so, why did the associated fuse fail to do its job? What do you think?
John Dunn is an electronics consultant, and a graduate of The Polytechnic Institute of Brooklyn (BSEE) and of New York University (MSEE).Related articles:
- A circuit simplification for AC power supply surge protection devices
- Protect POE systems from lightning surges and other electrical hazards
- Overvoltage transients: The silent killer