practice guide NAT'L INST. OF STAND & TECH

A 1 1 1 ( DS3D77

THE APPLIANCES

IN YOUR HOME

NIST

National Institute of Standards and Technology

Technology Administration

U.S. Department of Commerce
ABOUT THIS BOOKLET

This booklet has been prepared to help home dwellers, owners,

contractors, insurance agents and all parties interested in reducing

the number of cases and severity of equipment damage caused

by the unavoidable surges that occur in the electrical systems.

It is offered as a public service without any commercial

intentions. The information offered here is the result of collective efforts by several

experts on the subject, but presented in a simple format with practical hints on what to avoid and what to do. General principles are explained, but specific brand names are not discussed or mentioned as the technology and packaging techniques are

constantly evolving.

The need for protection - What is a "surge

A few words about other power problems

Source of surges - Lightning and other

How tough are today's appliances

Protection for the whole house

Protection at the outlet Good and bad installations Where and how to get help

Common questions and answers A few hints for your electrical contractor

ISBN 0-16-050782-0
HOW TO PROTECT THE APPLIANCES

IN YOUR HOME

What's a surge ?

The power you get from the wall outlet is known as "120

volts AC power." It can be represented by a sine wave

of voltage, as shown at the bottom of this page. The

power companies try to keep that voltage

uniform. Lightning, short-circuits, poles

knocked down by cars, or some other

accident can make the voltage jump to hundreds, even thousands of volts. The voltage spike shown on the left of this page is what

engineers call a "surge." A surge will last only a few

millionths of one second (the "blink of an eye" is thousands of times longer than the typical

surge). It is enough to destroy or to upset your appliances.

What can a surge do

to your appliances ?

Your appliances are designed to run on the normal 120 volts AC

supply, with some tolerance for more or less, but they can be

damaged, or their controls can be upset by surges. The

result is then frustration and repair bills, and even a fire in rare cases. See the next pages for a discussion of how sensitive\your

appliances can be to these surges.

Don't give up ! You can do something about it, your electrician can help

and even the power company can offer help, as this

booklet will show you - the why's and how's.

1
Other disturbances

.... and what they can do to your appliances

In the normal operation of a power system, unavoidable disturbances

other than surges also happen. They can upset electronic appliances,

but are unlikely to cause permanent damage. This booklet is concerned with surges and how to protect your appliances

against surges. However, just to give you an idea of what

these other disturbances can be, the graphs and words

below will give you the right words when you want to discuss a problem with your power company, your

electrician, and (hopefully, not any longer) an

electronics repair shop.

This is the voltage that we all take for granted, every second of the minute,

every minute of the hour, every hour of the day, every day of the year. But

occasionally, for a short time .... Normal line voltage

The voltage falls below normal: a sag.

Sags are unlikely to damage most

appliances, but they can make a computer crash, confuse some

digital clocks and cause VCRs to forget their settings.

Sag

The reverse of a sag is called a swell: a short duration increase in the line voltage. This disturbance might

upset sensitive appliances, and

damage them if it is a very large or very long swell. Noise is a catch word sometimes used

to describe very small and persistent

disturbances. These do not have

damaging effects but can be a

nuisance.

Noise

There is, of course, the ultimate disturbance: an outage - no voltage at all ! These disturbances are different from surges, but they should be

mentioned because the remedies are generally different. As we will see later, some available devices can help overcome both.

\ A A A A A

2
Sensitive appliances in your home

Your home contains all sorts, types or kinds of appliances. By "appliances,"

understand not only the traditional household helpers, but also the

entertainment electronics, the family's computer(s), smart telephones,

control systems (thermostats, garage door, etc.), and all the new things

to come.

^—— . / as power interruptions, but that is another story ...). To help sort out which types of your appliances might be damaged or upset,

you can describe them in general terms depending on their connections:

power, telephone, cable, or antennas. Each of these connections offers a path for a surge to come in, something that might be overlooked

when the cause of damage is explained as a "power surge."

The first type includes electronics that are connected only to the power, such

as a computer with no modem, a TV set with rabbit ears, a VCR not connected to cable TV, a table-top radio, a microwave oven, etc. Surge

protection of these is not particularly difficult, and quite often it is already built-in by the manufacturer.

The second type, for which more protection might be needed, includes

electronics that are powered, of course, from your power receptacles but

also connected to an external communications system: telephone, cable

TV, satellite receiver. A slightly different but similar situation, which

also needs attention, is that of appliances connected to a household

control system such as garage door opener, intrusion or fire alarm,

automatic sprinklers, or intercom.

We will see later why the two kinds of appliances face different risks of being damaged and consequently might require different protection

methods.

3
Where do surges come from?

There are two origins for the surges that occur in your power system: lightning

surges and switching surges. A few words about these will help you better understand what can be done to protect against them, and make good decisions on risks versus economics.

Lightning surges occur when a lightning bolt strikes between a cloud and objects on earth. The effect can be direct - injection of the lightning current into the object, or

indirect - inducing a voltage into electrical From circuits.

to Mother's

gentle touch

We will look at ways of protecting your

appliances against lightning surges that come by way of the wires - power,

telephone, cable, etc. Protection of the

house against the direct effects of lightning is done by properly grounded

lightning rods, a job to be done by

professionals t. Note also that lightning

rods are intended to protect the structure

of the house and avoid fires. They do not prevent surges from happening in the

wiring.

Direct lightning effects are limited to the object being struck and its surroundings, so that the occurrence is considered rare but it is nearly

always deadly for persons or for trees. Well-protected electrical systems

can survive a direct strike, perhaps with some momentary disturbances

from which they recover (blinking lights and computers restarting

during a lightning storm). The key word, of course, is "well-protected"

and that is why this booklet is offered to help your home have a well- protected electrical system.

Indirect lightning effects are less dramatic than from a direct strike, but

they reach further out, either by radiating around the strike, or by

propagating along power lines, telephone system and cable TV. From

the point of view of the home dweller, unwanted opening of the

garage door, or a surge coming from the power company during a

lightning storm, would be seen as indirect effects. Switching surges occur when electrical loads are turned on or off (by "Mother's gentle touch" or by some appliance

controls) within your home, as well as by the normal

operations of the power company. An analogy often given

is the "water hammer" that can occur in your piping if a

faucet is turned off too quickly: the electric current flowing in the wires tries to flow for a short time after the switch has been opened,

producing a surge in the wiring, just like the surge of pressure in the piping,

t You might find useful information about lightning protection on the Web - see page 20.

4
How often, how far, how severe ?

So, surges can and do happen ! These questions - how often do surges occur, how far do they travel before

hitting your appliances, how severe are they - must be answered, as well as possible, so that you can proceed to the next step of taking calculated

risks or making a reasonable investment by purchasing some additional

protection. There are several ways of getting surge protection, from

the simple purchase of a plug-in device from an electronic store (more

on that later) to the installation of protective devices for the whole

house, to be done by an electrician or the power company.

How often ?

You are probably best placed to answer that question if you have lived in your

neighborhood for several years. Lightning is random but can strike more

than one time at the same place. There are now sophisticated means to record the occurrence of individual lightning strikes; electric utilities and

businesses seek the data to make decisions on the risks and needs for investing in protection schemes. The reason for mentioning "several

years in your neighborhood" is that the frequency of lightning strikes varies over the years and the section of the country where you live t How far, how severe ?

The answers to these two questions are linked: a nearby lightning strike has more severe consequences than an equal strike occurring farther away.

There is also a wide range in the severity of the strike itself, with the very severe or very mild being rare, the majority being in mid-range (a current

of about 20,000 amperes for a short time) - but still much shorter than

the blink of an eye. Calculated risk or insurance ?

The trade off: A large stack of dollar bills and somte

change to replace your unprotected

computer, if and when a lightning or some other surge destroyed it or use a small number of bills to purchase a "surge protector" for peace

of mind and effective protection.

If you look at it from that point of view,

the choice is probably easy and, most

likely, you will be looking for one of those "surge

protectors" - or some device with a similar name

to do the same job, as explained next.

t Look on page 20 for information about lightning by surfing the Web.

5
What's in a name ?

When you walk in the computer store or electronic supply store, you might ask

for something to protect your appliances against surges, but what to call it ? The devices that can protect against surges are called "surge-protective

devices" by engineers, but that sounds too much like jargon to some people.

One name that seems to stick is "surge

suppressor" with a variety of trade- mark names. The Underwriter's

Laboratories chose to call them

"Transient Voltage Surge

Suppressor" and you might find that name or the TVSS acronym

next to the listing on the product.

Always make sure that the product

has been tested by a product safety testing organization, such as UL, ETL, or CSA, as indicated by their labels, as shown here:

SUPPRESS SURGE

DIVERT |WRC ) SURGE

You cannot really suppress a surge

altogether, nor "arrest" it (although your

utility uses devices they call "surge

arresters" to protect their systems). What

these protective devices do is neither

suppress nor arrest a surge, but simply

divert it to ground, where it can do no

harm. So a name that makes sense

would be "surge diverter" but it was not

picked. So, for the rest of this booklet, we

will stick with the more popular "surge

protector" and that's what you want to ask for when you walk in the store. ARREST SURGE

Then, when you get to the aisle where the surge protectors are on display, you

will most often find many brands, at different prices, so that the next question

will be "Which should I buy ?" That's a more difficult question to answer

because, while the principles and basic technology for these devices remain

the same, manufacturers come up with variations and improvements in their packages and trade names. So, instead, there are some points to look for on the packages that will steer you in the right direction. HOLD IT ! Before you run to the store and buy the most expensive surge protector -

under the assumption that more money automatically gets you a better protection - look at your personal situation. Asking yourself some simple

questions will help to decide how much surge protection you really need.

6
Decisions, decisions ....

Surge protectors come in many shapes and forms for many purposes, not just

the plug-in kind that you find in the electronic stores. There are several ways

to install them on your power supply: plug and play, do-it-yourself, hire a

licensed electrician to do it, or even call on your power company to do it. Here is a run down on your options, and who does it: Purchase one or more plug-in surge protectors

Install a surge protector at the service entrance panel

Have the power company install a surge protector next to the meter

Plug-in surge protectors

This is the easiest solution, and there is a wide variety of brands available in the stores (as we noted at the start of this booklet, we are not going to recommend brands). These come in two forms: a box that plugs directly

into a wall receptacle, or a strip with a power cord and multiple outlets. Depending on the appliance, you will look for a simple AC power plug-in, or a more complex combined protector for AC power and telephone or cable - more on that later. However, before you purchase the right

protector for the job, you should think about some details. There is another decision to make, concerning how a surge protector will power your appliance if the protective element should fail under extreme cases of exposure to a large surge or large swell. Most surge protectors are provided internally with some kind of fuse that will disconnect in case of

failure. However, this disconnect can operate in two different ways,

depending on the design of the surge protector: some will completely

cut-off the output power, others will disconnect the failed element but

maintain the power output.

Quit and be protected or continue ? \

For you, it is a matter of choice: would you want to maintain the output power

to your appliance - but with no more surge protection ? Or would you rather maintain protection for sure - by having the circuit of the protector cut off the

power supply to your appliance, if the protective function were to fail ? To make an intelligent decision, you must know which of the two

possibilities are designed into the surge protector that you will be

looking for. What are the lights telling you ?

To help the consumer know what is going on inside the surge protector, many

manufacturers provide some form of indication, generally by one or more

pilot lights on the device. Unfortunately, these indications are not standardized, and the meaning might be confusing, between one, two - even three or four lights - where it is not always clear what their color means. Read the instructions !

7
More decisions

So far, we have looked mostly at the plug-in surge protectors because they

are the easiest to install and they do not require the services of an

electrician. The two other possible locations for surge protectors are the

service panel (breaker panel) and the meter socket.

Service-panel surge protectors

Instead of using several plug-in protectors - one for each sensitive appliance

is sometimes recommended - you can install a protector at the service

panel of the house (also called "service entrance" or "breaker box").

The idea is that with one device, all appliances in the house can be

protected, perhaps with a few plug-in protectors next to the most

sensitive appliances. There are two types of devices available:

incorporated in the panel, or outside the panel.

Some breaker panel manufacturers also offer a snap-in surge protector, taking

the space of two breakers (assuming that there are blank spaces available on the panel), and easily installed by the home owner or by an electrician. However, there are two limitations or conditions to that approach:

(1) The snap-in protectors generally fit only in a breaker panel from

the same manufacturer - possibly down to the model or vintage of the panel.

(2) To install the snap-in protector, you must remove the front panel (do turn

off the main breaker before you do that !). Most cities have codes allowing

the home owner to do it, under some conditions. Check with your local authorities to find out if they allow you to do that, or hire a licensed

electrician to do the installation for you. There are other surge protectors packaged for wiring into the service panel,

either within or next to the panel. That kind of installation is best left to a

licensed electrician (as shown on page 19).

At the meter socket

There might be a possibility that the power

company in your area offers, as an option, to

install a surge protector with a special adapter,

fitting it between the meter and its socket (the

dark band in the bubble of the picture). But

that type of device and installation is out of the

question as a do-it-yourself project, and will require cooperation from the power company,

if they do offer the program.

Other types of outdoor surge protectors can be

installed near the meter. That kind of installation must be done by a licensed electrician.

8
Check list ...

Before you decide which way you want to protect your appliances, there are

other points to consider - perhaps this is a good time to make a check list. We have already mentioned the variation in lightning activity across the

country: Florida is known for very high lightning activity, the West Coast

for much lower (but not zero) activity. For a given area of the country,

the type of your dwelling, and what kind of appliances are to be

protected will influence which type of surge protectors you will be

looking for. Where do you live ?

This is an important question because the type of dwelling has some

effect on how severe your surge problem might be. In a somewhat

simplified way, consider three categories according to the

arrangement of the utilities: Detached house with power and telephone

and/or cable TV drops at opposite ends of the house - the worst possible arrangement

of all. But do not fret, there is a way of compensating, even after the fact, for this unfortunate situation, as we will see. Detached house with all services (power,

cable TV, phone) entering on the same side

of the house. You can improve that situation

further, as shown at the end of this booklet. Townhouse or apartment building with

services entering the building at one point

and fanned out to the different dwellings -

about the same as the case of the detached

house with all services on the same side. The first of these three arrangements has often been found to be made

worse by a violation (not intentional) of the prescriptions of the National

Electrical Code that require that the two incoming services be properly

bonded by a grounding conductor. Without going into fine details, the

problem arises because typically the power company and the

communications utilities do their own thing without enough

coordination. Statistics of insurance companies show that one

of the most frequent damage claims is for video equipment. A

possible explanation is the uncoordinated grounding of the

service connections by one of the utilities.

9
What appliances are you using ?

From the surge protection point of view, there are four kinds of appliances,

with examples listed below by order of increasing sensitivity to surges,

either because of their nature or because of their exposure:

Motor-driven and heating appliances

Washers (dish and clothes), food processors, power tools, heating and

ventilation motors, pumps, etc. Water heaters, space heaters, toasters, incandescent light bulbs

Free-standing electronic appliances

Computers without modem, table radios, TV sets with rabbit ears Compact fluorescent and modern tube-type fluorescent lamps

Communications-connected appliances

Computers with modem, TV with cable or satellite antenna

Fax machines, telephone answering/recording machines

Signal systems

Intruder alarms, garage-door openers, sprinklers, intercom

Let's then take a quick look at each of these and see which might need some

form of surge protection.

Motor-driven appliances and heating appliances

For each of these two categories, there can be two or more kinds, depending on

the type of control used.

Mechanical control (ON-OFF switch, rotary control, etc.), no sophisticated key

pad or other electronic control Electronic control (programmable operation, key pad, display, etc.) Appliances with mechanical controls are generally insensitive to surges and

can be expected to withstand the typical surges that occur in a residence.

Extreme cases, such as a direct lightning strike to the building, or one

to the utility, very close, might cause damage.

Appliances with electronic controls can be more susceptible to damage than

those with mechanical controls. Less traumatic but annoying can be upset

memory in programmable appliances, although progress is being made

in providing more built-in protection.

Another difference to be noted is that of appliances permanently connected, as opposed to those in intermittent use. The risk of a damaging surge

happening at the time of intermittent use is much smaller than that of an

appliance which is on all the time.

10
What kind of appliances ?

Electronic appliances

As soon as the word "electronic" is mentioned, your friends will tell war

stories of surge damage that can raise justifiable concerns. But fear

not; simple precautions and proper protective devices can go a long

way to avoid problems and replace those concerns by

confidence.

Power companies sometimes include as bill-stuffers the suggestion to disconnect your appliances when a severe lightning storm is approaching.

But that is no help if you are not in the house at that time. If, on the

other hand, you are in the house, pulling out the power cord of an

appliance that remains connected to a telephone line or cable

TV might not be the best idea: you would lose the grounding

of the appliance normally done by the power cord -

possibly a safety problem should a surge come

upon the telephone or cable TV. By showing you the basic principles of surge protection, this booklet should

help you make the choices that fit your needs for protection, without

overdoing it. To make the right choice, it is useful to note that there are two types of electronic appliances. For each of these types, a

different type of surge protector might be needed. These

types include:

Simple, one link connection to power the system

Dual connection to both power and communications

One-link connections

Examples of one-link connection of powered electronic appliances include a TV

set with "rabbit ears" antenna, a portable radio receiver, a computer with no modem connection or remote printer, a compact fluorescent lamp, etc. In the category of one-link connection we also find an old-fashioned

telephone connected only to the telephone system.

Note that most of these have a two-prong

plug, which is their sole connection to the

power system. For the TV set, a simple

AC plug-in surge protector on the power

cord would be sufficient. For just the

lamp, the cost of a surge protector

would be greater than the cost of simply replacing the lamp, if damaged

by a surge - and therefore not be justified.

One

cord

only

11
What kind of appliances ?

Two-link connections

This type of appliance is another matter. Typical of these would be a computer

with a modem, a video system with cable or satellite link, a phone system

directly powered from a receptacle (those with a large adapter plug

and a thin cable with jack which goes to the appliance generally

have sufficient internal isolation against surges).

The surge problem with this type of appliance is that a surge

coming in from one of the two systems - power or communications - can damage the appliance, because

of a difference in the voltage between the two

systems when the surge occurs. This can happen even when there are surge

protectors on each of the systems.

(For those of you interested in finding out why that is so, more on

that subject on page 18.)

Fortunately, you can find a special type of surge protector

against the problem, as described next. Equalizing differences

A simple solution to the problem of voltage differences for two-link

appliances is to install a special surge protector that incorporates, in the same package, a combination of input/output connections for the two

systems. Each link, power and communications, is fed through the

protector which is then inserted between the wall receptacles and

the input of the appliance to be protected. This type of surge

protector is readily available in computer and electronics

stores, and the electrical section of home building stores.

In addition to words on the package, it can be

recognized by the presence of either a pair of telephone jacks or video coax connectors in addition

to the power receptacles. Some models might have

all three in the same package. Do note a few words

of caution: (1) Read carefully the instructions or markings to find which is "in" and which is "out" for the telephone wires. It is important to note, before

you buy the product, whether your wall receptacles are wired for three-prong power cords. Some of these

combined protectors might not work very well if plugged into a 2-blade receptacle, using a "cheater"

plug. (On some, an indicating light will signal that.)

12
Not just power-line surges

Among other disturbances on the power lines, there was a brief mention of sags and outages on page 2. You are certainly and unhappily well- acquainted with outages that can occur for any number of reasons beyond the control of your utility. Sags - a brief decrease of the line voltage - can be more subtle and do occur more often than the

complete outage. You will notice these when the lights dim

momentarily, digital clocks or VCR controls blink, or your

computer shuts down then reboots - possibly losing some

data.

Industrial and commercial users, health-care facilities and other critical systems have for many years used a device called "uninterruptible

power supply" (UPS) that provides continuous power across a sag,

or for the first portion of an extended outage (an independent

local power generator set can then kick in). The aggravation of consumers caused by sags and outages has created a mass-market for consumer applications, making them affordable when

looked at as protection against these annoying (but not damaging)

disturbances - and with built-in surge protection as a bonus in many

cases. These consumer-type UPSs have a small battery which is sufficient to ride through any sag and short outages. Some

models even include the software to make a computer shut

down in an orderly sequence in case of a long outage.

Surges in other systems

So far, we have looked at surges on the power line alone, or on a combination

of power and communications lines. Surges of a slightly different kind can

also happen in parts of other electrical systems that do not directly

involve a power line. Examples of these are: the antenna for a remote garage door opener, the sensor wiring for an intrusion

alarm system, the video signal part of a satellite dish receiver. Surges in these systems are caused by nearby lightning

strikes. These other systems just mentioned have not been the subject of standards on surge protection as much as power and telephone systems.

Furthermore, protective devices for these other systems are not as

readily available to consumers. It is more difficult to offer well-defined

guidance on surge protection for these systems. Applying

preventive surge protection schemes to an existing system

might be difficult when the sensitivity of such a system to surges is not known. When considering installation of a new system, it would be a good idea to ask pointed

questions on that subject before signing the contract.

13
Protection for other systems

Some codes or practices aimed at providing safety for persons, when they are

correctly applied, can also provide some equipment protection.

For instance, the general practice of telephone companies is to provide a

surge protector as part of their services at the point where the telephone

line enters the house (in dense urban environments, the National

Electrical Code allows an exception). This protector is known as the

"Network Interface Device" (NID) and you will find it on the outside

of your house (see the drawing on page 19).

Another example of code requirement is that of cable TV systems for which

the National Electrical Code requires proper safety-oriented grounding

practices. The problem, however, is that in some cases, the video

equipment can still be damaged by voltage differences, as explained on page 12.

With the increasing popularity of small-dish

satellite receivers, installation by the user as

do-it-yourself has also increased. Typical

instructions for installation show how to make the connections, for instance in the

figure at right. What the figure does not show is the need to provide a combined

protector for power, telephone, and cable.

18" satellite dish

(stationary)

A well pump installed outside the house presents a double challenge: protecting the pump motor itself against surges, and protecting the house wiring

against surges that might enter the house by the

line that powers the pump. The first protection is generally built-in for modern submersible pumps.

The second protection should be provided by a surge protector installed at the

point where the power line to the pump leaves the house, using protectors

similar to those applied at the power line service entrance.

Grounding blockj

non-splitter

Intruder alarm systems using wires between sensors and their central control

unit can be disturbed - and damaged in severe cases - by lightning

striking close to the house. The wires necessary for this type of

installation extend to all points of the house and act as an antenna

system that collects energy from the field generated by the

lightning strike, and protection should be included in the

design of the system, rather than added later by the owner. Wireless systems are less sensitive than

wired systems.

14
Questions .... and answers

Among the questions often asked by consumers about surges, here is a

selection of typical concerns and simple answers. Q - When looking at the devices offered in the store, the packages show

specifications and claims that puzzle me. Can you explain ? A'S - Here are some typical specifications, and corresponding comments:

Joules - A (simplified) measure of the surge energy that the protector can dissipate without damage to itself. The higher the value, the more energy the protector can handle. Typical values range from about 100 joules, up to 1000 joules or more. Because this joule

number is often based on the three combinations of the wiring, many specifications

show the total joules rather than a breakdown among each of the three combinations. Maximum surge current (below) may give better information. Clamping voltage - A measure of the voltage-limitihg capability of the protector. An

oversimplified perception might be that the lower, the better. Many specifications show

330 volts for this voltage. This number is embedded in the UL standard values, but it is not a requirement. Somewhat higher clamping voltages, such as 400 volts or more, may be sufficient for protecting electronic appliances, and will make the surge

protector itself less susceptible to damage from "swells" (see page 2). Maximum surge current - A measure of the ability of the protector to handle surge current without damage to itself. You will find a range of values from several hundred to several thousand amperes. Even the lower values offered by manufacturers are sufficient for most surges, but a higher value will give you (generally for a slightly higher price) a comfortable margin of peace of mind. Speed of response - This specification appears on some packages, others do not even

mention it. Since practically all protectors use the same kind of technology for the

protective components, and their speed of response is inherently adequate for powerline surges, there is no need to emphasize a fast speed of response.

Internal protection - Some packages provide a description of what happens on the load side

of the surge protector (cut-off or still powered), should the protective element be damaged

by an exceptionally large surge or a long overvoltage. See on page 7 your choice, "Quit

and be protected or continue" - but now unprotected. Some packages also provide a cut-off and reset feature in cases of large swells, protecting the protector itself as well as the load. \

Indicating lights - See the discussion of their meaning on page 7. Be sure that you will remember the meaning after you have discarded the package. If a card with explanations is included in the package, save it because the meaning of the light - on or off, and what the difference there is among colors - is not always clear on

the device itself. If the protector maintains power on the load side, how often

will you look under or behind your desk to check and make sure that the

"Protection on" light is still on ? UL 1449 Second Edition - Some packages show "UL listed Second Edition" rather than the simple "UL Listed" found on others. It shows explicitly that the product has passed the most recent, improved tests for safety. Other standard symbols such as ETL or CSA

might be present instead of UL. They all represent the latest testing for safety. Guaranteed protection - A measure of the manufacturer's confidence in the actual performance of the product. As for all guarantees, do read the fine print.

15
More questions and answers

Q-lfl install one plug-in surge protector in one room, are the receptacles in other rooms also protected ? A - Yes, but only to some degree. The wiring in your house is split into several "branch

circuits" originating from your service entrance panel. If a surge protector is installed on a particular branch circuit, the other receptacles on the same branch circuit might benefit from it, but that benefit is much less on other branch circuits. To be more relaxed about protection in other rooms, it would be a good idea

to install a surge protector for each of the sensitive appliances in the house. This is especially true for the multi-link appliances because

of the problem explained on page 12. (See the next Q&A on whole-house protection and Figure 3 on page 19.) Q - Will a surge protector installed at the service entrance be sufficient for the

whole house ? A - There are two answers to that question: Yes for one-link appliances, No for two-link appliances. Since most homes today have some kind of two-link appliances, the prudent answer to the question would be No - but that does not mean that a surge

protector installed at the service entrance is useless. An important function of the service-entrance protector is to divert large surges coming on the power line, before they enter the house. A service-entrance surge protector makes the

protection by plug-in protectors easier but, as discussed on page 8, installation at the service entrance generally requires an electrician, unless you are a do-it-yourself person and your city code allows it. Q - Why single out two-link appliances as requiring special protection ? A - A first answer to that question is given on page 12, explaining the voltage

difference problem for these two-link appliances. A more technical explanation

is also given on page 18, intended for your electrician. Q -I have heard about surge protectors degrading over time: What about it ? A - Many, if not all, electronic components will age and have a limited life. The

question is really how long a useful life can a surge protector have. Today's well- designed surge protectors might reach their end of life prematurely if exposed to some exceptionally high and rare stress but, for those tested according to UL

1449 Second Edition, the way they fail should not be a hazard. The

prevailing opinion among specialists on surge protection is that most of the observed (and quite rare) catastrophic failures of surge protectors are caused by excessively high line voltage that can occur when

there is a fault on the power system. Failure from very large surges that might exceed the surge-handling capability of the

protector is less likely than failure from high line voltage.

And now, the "bottom line" question:

Q - How much money should I spend on surge protection ? A - It depends on too many factors to give a simple answer. Technology can

change, additional features beyond basic surge protection vary, stores offer "specials", and how much margin makes you feel comfortable is an intangible

factor. This booklet is not oriented toward rating product performance or

prices, but rather toward explaining the principles, so that you can make

an informed decision that will give you confidence.

16
Installation hints

As discussed on pages 7 and 8, there are several locations in your power

system where you can connect (install) a surge protector, depending on the

type of protection you desire and your inclination toward do-it-yourself or hire someone. These possible locations are shown in the sketch

below, with appropriate hints on how to go about the installation.

© Meter-base adapter

This is the most involved installation, requiring cooperation of the power

company if they allow it to be done by a licensed electrician. They might also

do it as part of their own program t.

(D Service panel, upstream

Also a job for a licensed electrician since the power cannot be turned off on

this side of the service panel t *.

(D Service (breaker) panel, snap-in

First opportunity as a do-it-yourself project, provided that the hardware is compatible and that local authorities allow the owner to do it.

Another possibility for do-it-yourself. The protector should be connected on

the load side of a pair of dedicated (spare) breakers in the panel *.

(D Receptacle, built-in

Provides same protection as a simple plug-in protector, but stays in place and

cannot easily be moved to another receptacle, should that become desirable.

© Plug-in (with cord or directly into receptacle)

The easiest of all for anyone to do. The only question is "Which to choose ?" Pages 15 and 16 have given you some elements for making that choice.

t It would be a good idea, to ensure compatibility, to ask the electrician to look into the ratings of the device and the power system available fault current. + The protector should be located close to the service panel (less than about 30 cm or one foot), otherwise the voltage-limiting effect will be degraded.

© o o done properly.

A very important point to keep in mind is that your surge protector will work by

diverting the surges to ground s

(see "What's in a name" on page 6) The best surge

protector in the world

* can be useless if grounding is not

(D Service panel, downstream

17
FOR YOUR CONTRACTOR'S EYES ONLY

(But it's OK to take a peek)

The problem of shifting reference potentials

According to insurance company statistics, two kinds of appliances are at the top of the

list as the most frequently damaged during a lightning storm: video systems (receivers

and/or VCRs) and computers with a modem connection. There is at least one

explanation for that very unhappy situation: if one of the two systems - power or communications - brings a surge to the house, the intended operation of surge

protectors creates a difference in the potentials of the references across the two input

connections of the appliance, causing failure.

In the set-up of Figure 1, a personal computer (PC) is connected to both the power

system and the telephone system, and we assume that a surge is coming along the telephone wires. The surge current ("Surge I" in the figure) flows from the telephone

system toward the common grounding point via the network protective device (NID) at the point of entry, and the grounding conductor mandated by the National Electrical Code

(NEC ®). This current produces a magnetic field that couples into the loop formed by the power branch circuit, the telephone premises wiring lines to the PC, and the bonding

conductors. A voltage (Vdiff) is induced in the loop and appears across the power input

and telephone input of the PC, with upsetting or damaging consequences. The presence

or absence of surge protection on the AC side (Arrester or SPD) has no effect on the

coupling. One effective solution is to have the consumer install a combined protector, as

explained on page 12.

Telephone — System

Figure 1 Shifting of reference

potentials between

power and telephone

Surge i

Even though this installation complies with the NEC, the situation is made worse if the

point of entry for power and the point of entry for communications are at opposite ends

of the house, with a large loop separating the two cables. The 1999 NEC now limits the separation between points of entry to 20 feet (7 meters) for new installations. The

situation is even worse yet when the incoming service, cable TV in particular is not bonded to the power service ground. That is a clear violation of the NEC but experience

has shown that it is not so rare, and the result can be severe damage to the appliance.

NEC® is a registered trade mark of the National Fire Protection Association

18
FOR YOUR CONTRACTOR

Recommended integrated bonding

The recommended bonding arrangement shown in Figure 2 is applicable for new construction or for existing homes where an opportunity occurs to relocate

the point of entry of the cable TV or the telephone NID. It is compliant with the

NEC minimum requirements for safety, and will reduce the problem of shifting

reference potentials just described by inter-system bonding of all utilities serving a residence. The usual components for each service connection are simply

installed next to each other. Another possibility for reducing the shift in reference potentials is to install an

integrated, multi-utility surge protection at the breaker panel, as shown in Figure

3. This device includes appropriate surge protection for all three services: AC

power, telephone, and cable TV, with the minimum length for the bonding

arrangement.

Figure 2

Recommended

Inter-system

bonding

Ground to Service Panel —

j Revenue Meter INTERSYSTEM BONDING POINT

Telephone Network

Interface Device

i Signal From Cable 5L

#6 AWG Bare Copper

(13.3 mm*)

video Signal To TV Sets

To Ground Rods

Figure 3

integrated multi-protection

device for service panel

installation

Standard Breaker Panel —

19
WHERE TO GET MORE HELP

There are many sources of information on surge protection, including codes,

standards, handbooks, and many technical papers. Most of these are

written for technically-oriented people rather than typical consumers,

with the exceptions of the bill-stuffers from your utility, occasional

consumer-oriented articles, or the present booklet. On the other hand, with the popular

and ever-increasing use of the

Internet, useful information can be obtained on line. The sources identified below are listed as a starting point for a Web search,

but with the understanding that new ones can appear and existing ones

can disappear. Furthermore, these sources include some

commercial entities as well as non-profit organizations. Such

identification is not intended to imply recommendation or endorsement by the National Institute of Standards and

Technology, nor is it intended to imply that these sources are necessarily the best available for the

purpose.

Weather and lightning information:

http://www.accuweather.com/wx/services

http://www.lightningstorm.com

http://www.lightningsafety.com

http://www.nfpa.org

Surge-protective devices

http://www.nema.org

Wiring practices

http://www.necdirect.org

Power quality

(Surges, sags, and outages)

http://www.epri-peac.com

* NEC® is a registered trade mark of the National Fire Protection Association

20
U.S. DEPARTMENT OF COMMERCE

Donald L. Evans, Secretary

National Institute of Standards and Technology

Karen H. Brown, Acting Director

NIST Special Publication 960-6

May 2001

Electricity Division

National Institute of Standards and Technology

Gaithersburg, MD 20899-8110

National Institute of Standards and Technology

Special Publication 960-6

Natl. Inst. Stand. Technol.

Spec. Publ. 960-6

20 pages (May 2001)

CODEN: NSPUE2

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 2001

For sale by the Superintendent of Documents

U.S. Government Printing Office

Internet: bookstore.gpo.gov

Phone: (202) 512-1800 Fax: (202) 512-2250

Mail: Stop SSOP, Washington, DC 20402-0001

Co-Sponsors: EPRI

Illinois Power Company

State Farm Insurance Companies

Text by Francois Martzloff based on Special Publication 0545. R,

Recommended Practice for Protecting Residential Structures and Appliances

Against Surges,

EPRI PEAC Corporation, Knoxville TN.

[Available at http://www.epri-peac.com]

Cover and illustrations by Susan Spangler
May 2001