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The Myth of Whole-House Surge Protection

Surge protection at individual components or circuits is the only way to protect against internal surges.


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Wouldn't it be wonderful if we could put an air filter in Chicago and filter all the air in America? A good idea, but it can't possibly work effectively. That's why a service entrance powerline surge protector -- often called a whole-house surge protector -- does not live up to the billing.

Just like the Chicago air filter, a service entrance surge protector can provide some protection from the 20 percent of surges originating outside a house, but not the 80 percent of surges which originate within a house.

Where Do Surges Come From?


For a better understanding, you need to know that:
  • 20 percent of surges originate outside a house from nearby lightning strikes, which couple surges into nearby power wires
  • Normal utility operations can cause electrical disturbances
  • Perhaps the most common external surge source is when power is interrupted for any reason – a tree falling on wires, a car hitting a pole, wind damage, utility repairs, etc. Wires conducting electricity create a magnetic field. When power is interrupted, the magnetic field collapses, inducing large voltages in the wires. A 12-volt spark coil relies on this principle to generate many thousands of volts to fire spark plugs.
  • 80% of surges come from within a building are generated every time equipment cycles on and off.
Internal surge levels are related to the magnitude of current being interrupted and the length of wire from the service entrance to the load.

The longer the wire and the higher the current, the bigger the surge generated when the power is interrupted. A classic example is a coffee pot located far from the service entrance. Every time the heater kicks on and off to maintain the coffee temperature, significant surges are generated. It should be obvious that a coffee pot cycling on and off several times an hour is a much more frequent event than a tree falling on the power wires, or a lightning storm.

2 Technology Choices


Two basic surge protection technologies are available today with radically different performance and endurance. The dominant technology is sacrificial shunt mode technology. Typically, this technology uses MOVs (metal oxide varistors.) The second is series filter technology.

The shunt mode (MOV) technology relies on a three-stage, or zoned approach to whole-house protection:
  1. Service entrance protection
  2. Branch circuit protection
  3. Point of use protection
Service entrance and branch circuit protection must be installed by licensed electricians. The point-of-use plug-in protection should be used with each piece of sensitive equipment.

These products generally incorporate "protection working" lights or alarms since they use sacrificial components (MOVs) that should be periodically replaced to maintain protection as the protection degrades with exposure. In many instances, it is impractical to have service entrance and branch circuit protection. Either an electrician would need to install and periodically inspect the service entrance and branch circuit protectors or the homeowner would have to rely only on the point-of-use plug-in products. In these cases, the shunt mode plug-in point of use protectors have much greater exposure, and may not even be rated for the level of exposure they will see.

Related: 3 Big Smart Home Trends

With series filter technology, plug-in point-of-use filters are available that can repeatedly eliminate damaging surge energy and noise. This eliminates the electrician-installed service entrance and branch circuit protectors needed by the shunt MOV technology. Since there are no sacrificial elements in the filters, routine maintenance and concern about protection level is eliminated. "Protection working" lights are not required since filters do not "wear out" with use. Advanced Power Quality filters are now available that cancel out the worst-case powerline surges and noise and have at least a 10-year life with the worst surge.

Powerline surges consist of a brief burst of high-frequency energy. The power frequency is 60 Hz. Surge frequencies are 20,000 Hz and higher.

A filter that removes the surge frequencies will eliminate not only the surge but also the associated noise. Removing powerline noise has the added benefit of improving the quality of the A/V signals.
Filters work continuously. Unlike shunt mode clamping circuits that do not begin to suppress a surge until the clamping level is exceeded, the continuous operation of a filter can be much more effective.
In fact, modern Power Quality Filters have been shown to filter and cancel out surge voltage to such an extent that protected equipment will be unaware a worst-case surge event has even occurred.

Couple this with a 10-year life for point of use applications, and you have a worry-free, noise free, maintenance-free electrical environment.

Safety Certifications


Underwriters Laboratories has a UL 1449 Safety category for "Surge Protective Devices" (SPDs). This covers the older shunt mode technology.

Filter technology is covered under UL 1283 "Electromagnetic Interference Filters."

Meanwhile, Modern Power Quality Filters under UL 1283 can be effective and reliable at surge suppression. They operate over a wider voltage range than products called Surge Protective Devices (SPDs), which are under UL 1449.

Rudy Harford is chief engineer at Zero Surge Inc. He holds over 40 U.S. patents in the field.

Related: 3 Big Smart Home Trends


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Article Topics

News · Power Protection and Management · Power Protection · Power Protection · All topics

About the Author

J. Rudy Harford
Rudy Harford is chief engineer at Zero Surge Inc. He holds over 40 U.S. patents.

10 Comments (displayed in order by date/time)

Posted by jeff g  on  12/20  at  02:24 PM

Ahh, just get a home owners insurance policy that covers surges and be done with it. Plus it lets you “upgrade” your electronics every time there’s a surge!

Posted by Surge  on  12/21  at  08:20 AM

Ah, and don’t forget that you’ll be able to “uograde” your insurance carrier right after your first claim… when they decide not to renew your policy.

Posted by jason  on  01/06  at  11:11 AM

Huh, guess what Zero Surge, Inc. sells?

Posted by Stephen Brown  on  11/24  at  01:55 PM

j rudy is one of the most talented power related electrical engineers in the country….you should listen to him…...

Posted by Jay  on  04/09  at  02:48 PM

If you use a whole house surge protector u do indeed get more than just protection from the “20 percent” that this gentleman claims. He’s omitting the directly connected breakers for your major appliances, HVAC and other possible directly fed “circuits” (breakers). They indeed are protected at the panel from internal surges from other equipment coming back into the panel from other circuits. If the equipment is so good that this gentleman is referring to, why is it only warranted for 10 years? Also, a layered (multiple protection levels) approach is always better than a single point of use protection scheme. This guy is selling his protectors with this article is the bottom line and he can’t offer a whole house protector.

Posted by gary m  on  10/25  at  01:05 PM

Yeah, nearly all of those 80% of internal power surges are too small to damage your electronics. It’s those 20%, most of which are external, that do the damage. A whole house surge protector combined with surge protection at the electronics is the way to go. When you need stable, filtered power get a big smart UPS.

Posted by Guy  on  01/10  at  01:00 PM

Like Gary said, the 20% is what you need protection from, the surges from lightning or your power supply is what can fry all your electronics. Its like saying Chicago 80% windy so the only thing that will help is shutting the windows. Well if only 20% could blow your whole friggin roof off, that is what you want protection from.

Posted by Mike  on  01/21  at  09:21 AM

I don’t agree with this article completely. The only time I actually suffer damage is when the power company has faults. You can’t protect your z-wave devices with individual protection. Last power outage I lost a z-wave power switch and a surge protector that was only computer and then the computer power supply. This circuit is very close to mains.
Hour analogy was also very poor. We are not trying to protect a city against surges, just a house. Better analogy would be to filter and treat the air to a house. Oh wait, that actually can be done.

Posted by Marv  on  06/09  at  06:17 AM

FYI - most newer electronics with their own internal power supplies do provide some surge protection for that device only.  I’ve had lightening twice take out ALL appliance control boards and panels, hifi receivers, and TVs, but never had a device damaged by a surge internal to the home.  All our sensitive electronics are now protected by high wattage UPS connections which do provide limited lightening surge protection.  Someone ought to invent a master circuit breaker that is fast enough to stop most of the outside surges but I guess that’s too much to ask.

Posted by John  on  07/09  at  11:37 AM

This article is pretty vague and doesn’t offer any understanding on the actual components of the specific type of power line filter that he’s talking about or how they work. And you’ll have to do a lot of searching and reading just to figure everything thing out, so I’ll try to condense/distill everything here for you.

Most companies that sell surge protectors such as APC etc. sell, what they call A/V power line filters (A/V standing for audio/visual meaning your tv and speakers etc.) right next to their regular surge protectors, only difference is, there is none, because most power line filters with surge protection use MOVs as their surge protection in conjunction with some sort of filter.

The type of surge protector he’s talking about, is called a Series Mode (SM) surge suppressor which works completely different from an MOV. SM suppressors actually absorb voltage spikes through a series of inductors capacitors and resistors and are not rated in joules.

The only thing I’m not exactly sure of is the difference in filtering. From my understanding and readings, SMs use low-pass filters which are rc circuits that allow only certain frequencies through while blocking and diverting others and suppressing surges by using capacitors resistor…etc. MOVs can use filters as well, I’m just not sure as to the type, some sites mention “isolated power filter banks” which seems to suggest that they use CMCs (common-mode choke) but I can’t be sure because most sales associates aren’t electrical engineers and neither am I.

The main thing to worry about though, is not noise on the line but surge protection and SMs seem to be the best option, they just filter out high/low frequencies as well. Now whether this is a product of it’s design (eg. it can’t function or is dangerous without it) or something added as a side benefit that they can sell to you, I don’t know. But what I do know is that Zero Surge Inc. is one of the few (possibly the only) companies that actually sell SMs, this could be because they have some patented technology with their SM that’s far superior to what other companies can offer or companies don’t want to make SMs because MOVs are cheaper to produce and have higher profit margins.

Well I hope you learnt something today as I did and you can check out this article which explains things a little clearer http://www.pcmag.com/encyclopedia/term/52279/surge-suppression
they also mention uninterruptible power supply’s, for that you can check this http://electronics.howstuffworks.com/everyday-tech/surge-protector5.htm

and you can read more about SMs
http://www.surgex.com/surgetypes.html
http://www.bryston.com/PDF/newsletters/Bryston_Newsletter_V9_2.pdf
http://en.m.wikipedia.org/wiki/Surge_protector#Series_Mode_.28SM.29_surge_suppressors

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