Buying some new home theatre stuff this week, and it occurred to me that I ought to consider protecting my investment. I’ve been reading about surge suppressors, and was not surprised to find that they can’t be trusted to protect against lightning strikes, which deliver ludicrous voltages/currents/energies/powers. Any way you slice it, lightning is bad-ass.
And so now I’m wondering, what is the source of the surges against which surge suppressors are intended to protect? Typical clamping voltage for a surge suppressor is 300-400 volts, with a surge energy absorption rating of 500-2500 joules. Apart from a newsworthy short-circuit at the substation down the road, what sort of event could cause a spike in line voltage that exceeds 300-400 volts by a significant amount?
Umm, only if it close by. A hit a few blocks away can cause a medium size problem, and not just the juice in the bolt directly, it can take a few seconds for the effects on the grid to settle down. So there’s a small circle around your home that it won’t help but a very large circle that it will help. Guess how much more likely there’s going to be a strike in the big circle than in the little circle.
We get odd power glitches all the time here even in good weather. Transformer’s blow, lines get knocked down, etc. Maybe not a 400V surge but it helps.
Other people turning electrical things on and off.
The equipment in the auto repair shop down the street. the AC & refrigeration for the local grocery store. The freezers in the nearby restaurant. Even just the neighbor who does woodworking in his basement.
You’re all on the same electrical source, and every motor that starts up or shuts off generates a voltage spike of varying size. Sometimes they cancel each other out; sometimes they reinforce each other. Mains electrical power starts out fairly clean at the generating plant, but after going through all the system to your neighborhood, and then facing all the constant on and off of electrical loads from everyone in the neighborhood, the power coming into your house is really quite ‘dirty’.
So most expensive electrical equipment, like computers & TVs and such have some protection built in to their power supply. But adding more protection is a good idea. Some houses are now being wired with whole-house surge protectors in the main electrical box. Probably a good idea, as more & more appliances are smart ones, with electronic circuit boards inside – these can be vulnerable to dirty power, and can be very expensive to replace.
This will address your questions and some myths posted by others.
All appliances contain surge protection. Must (so-called) surges are nothing more than nose - made irrelevant by that internal protection. Many foolishly believe popular myths about surges from motors - because they did not view the numbers.
We install surge protection so that the rare and destructive surge cannot overwhelm internal appliance protection. Will 500 or 2500 joules stop and absorb a surge of hundred of thousands of joules? Of course not. Any yet that is how ineffective protectors are promoted.
From the NIST:
> You cannot really suppress a surge altogether, nor
> “arrest” it. What these protective devices do is
> neither suppress nor arrest a surge, but simply
> divert it to ground, where it can do no harm.
But plug-in protectors are promoted by “arresting” a surge. NIST says surge energy must be dissipated harmlessly in earth. That means the rare and typically destructive surge need not even enter the building.
Notice the important word - ground. How to identify the ineffective protector. 1) has no dedicated connection to earth. 2) Manufacturer avoids all discussion about earthing. That applies to most every plug-in protector as well as the many who promote a ‘protector’ only because it sounds like ‘protection’.
Essential to earthing is a single point ground. All incoming wires must be earthed to that same earthing electrode. Did you know all telephone lines already contain a ‘whole house’ protector? Find you NID (where their wires meet yours). Is that box (protector) earthed less than 10 feet to the same electrode used by cable and AC electric? Short to ground is essential. Also, the wire must be without sharp bends, no splices, separated from other non-grounding wires, not through conduit, and again - short.
Same applies to the ‘whole house’ protector installed in the breaker box. More responsible companies such as GE, Siemens, Keison, Polyphaser, Leviton, Square D, Intermatic, and Cutler-Hammer provide ‘whole house’ protectors. One means protection for everything in the house. The Cutler-Hammer version sells in Lowes for less than $50.
Since earthing is so critical (and never discussed by scam protectors), well, earthing must meet and exceed post 1990 National Electrical Code. Nothing inside a building need be upgraded. But that earthing is where surges dissipate harmlessly.
BTW, cable needs no ‘whole house’ protector. Cable can be connected directly to earth. Therefore no protector required. Appreciate what the protector is. Some wires cannot be connected directly to earth. So we install a protector. Cable needs no protector; can be earthing directly. What provides protection? Not the protector. Earth ground is the protection. At this point, reread that NIST paragraph. Appreciate how many protectors are sold that do not even claim to protect from the typically destructive surge.
Well the NIST then gets even blunter:
> A very important point to keep in mind is that your
> surge protector will work by diverting the surges to
> ground. The best surge protection in the world can
> be useless if grounding is not done properly.
For same reasons that a majority knew Saddam had WMDs, a majority will also recommend protectors that simply violate basic protection methods. Will that plug-in protector absorb hundreds of thousands of joules? Will it stop what three miles of sky could not? That is what the majority assume when recommending plug-in protectors.
Why does your telco not waste money on plug-in protectors? They need that computer protected from about 100 surges during every thunderstorm. So every incoming wire in every cable is earthed via a ‘whole house’ protector before entering the building. This is how surge protection was done even 100 years ago. That well proven. But plug-in protectors simply violate those principles - do not even have that always required short (‘less than 10 foot’) connection to earth.
Where does that energy get dissipated? What is the path that surge current flows through? Answer those questions to answer yours.
We install a ‘whole house’ protector so that even direct lightning strikes cause no damage. An effective protection system means you never even knew a surge existed. Means even the protector is not damaged due to a direct lightning strike. This is, after all, well proven for the past 100 years. How often does your telco disconnect their computer with each approaching thunderstorm? How often is phone service lost all over town for four days as they replace that computer? Why is a computer connected to overhead wires all over town not damaged from 100 surges during each storm? Protection is that routine everywhere in the world. And still a majority will recommend protectors that have no earthing AND do not even claim to provide that protection.
The ‘whole house’ protector that makes lightning irrelevant also makes other surges irrelevant - including ones supposedly generated by electric motors. But again - and this is most important: a protector is only as effective as its earth ground.
Above is secondary protection. You must also inspect your primary surge protection system: http://www.tvtower.com/fpl.html
What defines each protection layer? The only component required in every protection system: single point earth ground.
BTW, this is only a summary answer. Effective protection is that well understood in even greater detail. Concepts even demonstrated by Franklin in 1752. If you really want to learn about this, you should have reams of questions.