As I understand it, the MOVs on your typical surge protector continually degrade until the ability to absorb excess energy is no longer adequate. As such, you should replace surge protectors before the protection capability wears too low.

Well, if that's the case, then how is it that when you buy a surge protector from, say, Snap, there are no guidelines about when to replace it. In fact, there isn't even a mention of the fact that the protection degrades!?

And, since there is no visibility into the condition of the MOVs, how do you determine when to replace the surge protectors?

Also, if the surge capability degrades, then isn't IP controllable surge equipment a bad way to go? Shouldn't you instead use IP controllable outlet strips (and move the surge protection upstream of those strips), so that you don't need to replace the costly IP infrastructure when the protection degrades?

I'm not sure there's a way to estimate the life of this kind of device without knowing the quality of the power delivered. Most of what I have read recommends layers of protection, starting at the breaker panel with whole-building protection devices and then using something at the equipment, to catch surges that come from motors, switches and other sources IN the building.

Check out Surgex's booth at Cedia. They discuss exactly the problem you're talking about and why their equipment is better than MOV based protection.

Just to be clear, MOVs do not just degrade over time. They degrade when they handle a surge (when they conduct). Catastrophic failure of the MOV happens when the surge is more than its capacity.

It is impossible to know how much life a MOV has left in it. Many surge protectors have indicator lights, to let you know when the protection has failed. But an MOV based protector can be on the verge of failing (with little protection left in it) and that light will not be lit until it gets zapped for good.

This seems like a significant shortcoming in our industry. You’d never think of installing expensive electronics without installing adequate surge protection, and yet it seems there are tons of projects out there with inadequate protection by virtue of having degraded MOVs.

I don’t get why this doesn’t get more attention in the trades, by vendors, in the forums, etc.

What are you all doing about this on your projects?