[aceazzameen]

I've always known surge protectors age and eventually stop protecting from surges. But what I always wanted to know is how can you tell when it expires? I'm assumings it's based on how good/bad/stable the electricity is in your area. But still, is there any way to know when it's time to replace?

[malfist]

Typically surge protectors have a little light to let you know if the surge circuitry is still good. Others will fail safe, meaning the won't power on if the circuitry is bad. Cheap ones may do neither.

Either way, if your house has had a surge and other equipment has died that wasn't surge protected, probably a good time to replace all surge protectors in the house, they're not really meant to survive multiple large surges. They shunt the power destructively, just somewhere you don't care.

[neilv]

> they're not really meant to survive multiple large surges. They shunt the power destructively, just somewhere you don't care.

Is this a concern when buying used rackmount power conditioners (like used for live music setups?), to protect home IT gear? Can they be worn out without a sign that they are?

[cesarb]

What I've read is that their main failure mode is that, as they age, their trigger voltage gets lower and lower, and at some point the normal line voltage is enough to trigger them all the time. And when they overheat, either due to being triggered all the time or due to diverting a large surge, they fail open and no longer have any protective effect on the circuit. High quality surge suppressors would have fuses physically touching the MOVs, so that when a MOV overheats and fails, the fuse opens and cuts power to the now unprotected output.