Re: Whole House Surge protector
All MOV surge supressors have a "joule rating." A power surge is also measured in joules. MOVs get used up. So if you have a 5,000 joule MOV, and you get a 20 joule surge, the MOV is now good for 4,980 joules. (That's a BIG surge suppressor. Most are rated 500-1500 joules, and that rating is the sum of all the MOVs in the supressor. So if you've got a 1200 joule supressor, that's probably 400 joules hot-neutral, 400 joules hot-ground, and 400 joule neutral-ground. The 400 joule neutral-ground is unlikely to ever come into play, so your effective rating is more like 800 joules.)
As you can see, eventually it will wear out and will no longer be able to protect your appliances. That's why it's a good idea to replace the surge protectors for your electronics every several years (more often if you have dirty power or a lot of electrical storms).
Some have LEDs that indicate protection is working. They do not tell you when it is *almost* used up. So if there's only 100 joules left and you get a 200 joule surge your appliances and electronics are toast. (That's a BIG surge you'd only see in a direct lightning strike or a primary utility line contacting your residential feeder.)
That said, there are SOME surge protectors that will interrupt the circuit when they fail. I'm not aware of any whole-house protectors that provide this kind of protection.
Last edited by Fencepost; 10-27-2011 at 01:21 AM.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.