Any device that challenges electricity for a living is going to lose a battle sooner or later. So, what's a surge protector to do when it can no longer provide surge protection?
One possibility is to visually indicate the failure, either by turning a light on or off or by changing the color from green to red. The problem with this is that the light may not be visible because the surge protector is buried in a corner. Plus, who's going to know what the light means years after the device was put into service?
Another possibility is sounding an alarm. Personally, this isn't the sort of thing I want to be woken up for in the middle of the night.
The most important issue after a failure, however, is whether the surge protector should continue to power the devices plugged into it.
That is, do you want the convenience of your stuff continuing to work unabated, or, do you want to go the safe route and have the surge protector not provide any power, when it can no longer protect against surges.
Being into Defensive Computing, I opt for safety. Not providing power insures that even a deaf and blind Pinball Wizard (the Who's Tommy) would be aware that his surge protector had failed (the Pinball machine wouldn't work).
In a recent blog here I described the somewhat pricey Tripp Lite ISOBAR4ULTRA whose documentation says that it provides unprotected power after a failure, and, the relatively cheap APC NET8 that promises not to provide power that it can't protect.
In a comment on that blog, someone claiming to work for Tripp Lite disputed their own documentation and basically said that APC was lying in theirs. But, of course, you can't trust anonymous comments, so I contacted each company for an official comment.
APC responded, Tripp Lite did not.
Mark Kaloudis, Senior Product Manager at APC said
With respect to the statement made by the person claiming to be from TrippLite, it is false.
The NET8 is designed to take many hits and keep on working. In the event a MOV between Line and Neutral were to fail, a thermal fuse would open up, preventing any power from being passed to the load. This would mean the load would be protected, although it would not be receiving power.
The NET8 has a lifetime warranty however, so we would replace it free of charge. Ultimately, the NET8 also has a $100,000 Equipment Protection Policy, which is in essence our guarantee that it will work as advertised.
The NET8 has been around for a long time. It was first introduced in 1997 and is still selling well (meaning there are a lot of satisfied customers using it). We added a feature to our website in the last couple of years that lets our customers review our products so I looked at the reviews for the NET8. Interestingly, one of the reviews describes the specific behavior we are talking about. Here's a link to the review on our website.
The judgment still stands. APC surge protectors are the Defensive Computing choice.