So I was swapping digging stories with a guy today and he told me about his 2 friends who both experienced HUGE power surges that damaged several pieces of electronic equipment. One guy hit a power line in his backyard while drilling fence post holes. He was 6 feet away from where the line was marked! Anyhow, he had a whole house surge protector installed and still several pieces of equipment got fried. Imagine what might of happened if he didn't.... Wait a minute, isn't that the point of the freakin' surge protector in the first place? So you gotta wonder - how good are these units and are they worth having? I heard it's about 400-500 clams to get one installed. That's a good chunk of change for something that might not work.
BTW, the power company wrote the guy a cheque for the replacement cost since hitting the power line beyond 2 feet of where they mark is considered their fault.
I'm currently digging a trench across my power line - scary.
We redid our electrical in March this year and our electrician, who is also a friend, recommended having it installed. Cost for this probably varies by location and it was only a couple of hundred dollars for us to do which seemed like a no-brainer. Besides various computer equipment we also have a pretty nice home theatre I was trying to shield.
He did say that this surge protector at the panel wasn't necessarily to replace the surge protectors you have at the outlet, and recommended we keep those in place. It just acts as the first line of defense and, as I understand it, only protects you from power surges coming off the pole as it enters the house. Don't quote me on that one though.
Surges can also come in via the cable or telephone lines, so it's not 100% protection.
(When we had our electronics sale/repair store, our technician used to phone my husband, cackling with glee and rubbing his hands together, when we had a thunderstorm rolling through the area. They'd get all sorts of work repairing surged equipment, and then sell bunches of surge protectors to boot.)
The surge protectors work, btw - some better than others, noting the caveat about the cable and telephone lines. Can't protect against unexpected surges, but it never hurts to unplug everything if a thunderstorm is in the area, or if your power has been disrupted - lots of surges happen when the power comes back on.
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Surge protectors are good at providing protection from large transients, like that from lightning hits - but not so good if it is an unusual rise in line voltage that is below the trip point of the varistors. Such whole house devices not only have some rather massive varistors, but employ spark gaps, so you really need to have an effective return to ground for it to work.
The varistors work by "crowbarring" the circuit, that is, when an over voltage occurs, they start to conduct all of the current, so that in effect, it shorts the line out and trips the circuit breaker. Because of this, the varistor has to be overrated so that nominal line increases don't trip the breaker, and that there is a finite delay in tripping even a fast acting breaker. I would say it is a good addition to have, especially in the country or on high ground, as a first line of defense in order to keep regular electrical devices from shorting out. For instance, a "double insulated" device is supposed to be able to stand off 3000 volts, while a grounded device is supposed to stand off 1500 volts.
Electronic equipment is far harder to protect - especially since most modern devices employ switchmode power supply topologies that can't tolerate over voltages on the inputs, as there is no transformer to soak up excessive transients. Of course, if one does careful design work, one can resort to a "saturable core transformer" which will entirely block over voltage conditions - but the problem is that a SCT runs very hot if not loaded down close to it's power rating.
Thus, secondary protection is of some assistance, like surge suppressing power bars or special Corcom line filters which many deviced have built in. Proper grounding is key for these protection systems to work. Plus, if there is a surge, it will tend to destroy the varistor built into the power bar - so many people think they have protection but don't. There is no easy solution, but if you are in an area where such electrical events are common, I'd go whole house, perhaps with adding extra grounding outside to bind to, and continue to use surge protection where ever you have equipment locally in the house.
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I've never put much faith in surge protectors (particularly since most people don't know the difference between a surge protector and a power bar that has a little circuit breaker and multiple outlets) - as noted above, by the time it trips, the damage is done.
I *have* put my confidence in UPS systems - like the APC backup units - thinking that the battery acts as a buffer. Am I misleading myself?