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Surge Protective Device (SPD) Information and Advice

Levi Zeigler March 04, 2018 0 comments

Why would any building need any surge protective device (SPD)?

Very few people realize it, but your electrical components in any building is under constant attack every day by power disturbances and electrical surges. Power Disturbance studies indicate that the electrical utility causes twenty-twenty-five percent (20-25%) of power disturbances but the other seventy-five-eighty percent (75-80%) are caused by electrical components and wiring within buildings.

What are some types of power disturbances?

These are just some a few:

  1. Power Outages
  2. Power Failure
  3. Partial Power Failure
  4. Over Voltage (Power Surge/Power Spike)
  5. Under Voltage (Power Sag)
  6. Switching Transients
  7. Harmonic Distortion
  8. Electrical Line Noise
  9. Equipment Failures
  10. Electromagnetic Compatibility (EMC)
  11. Electromagnetic Interference (EMI)
  12. Power Quality Phenomena
  13. Earth Potential Rise (EPR)
  14. Ground Potential Rise (GPR)
  15. Power Factor Below 1

What harm can a power disturbance or electrical surge do?

These are just some just a few:

  1. Personal shock hazard
  2. Fire hazard
  3. Total equipment failures
  4. Partial equipment failures
  5. Intermittent equipment failures
  6. Shorten life cycles for each electrical device.

What are some warning signs that my building or home has had a power disturbance or electrical surge?

  1. These are just some just a few:
  2. The obvious signs are no electrical power or and electrical device is no longer operating.
  3. Light bulbs have a very short life span
  4. LED displays have portions of the digit or letter missing
  5. Computer controlled devices freeze up and need to be rebooted
  6. Lights dim when an electrical motor starts up
  7. Shorten life cycle for electrical devices.

What are power surges?

Power surges are extremely brief spikes in electrical power that can destroy the electrical circuits inside appliances and electronics. Not only can power surges destroy appliances and electronics, they can ruin electrical outlets, light switches, light bulbs, air conditioner components, and garage door openers.

How can you protect building or home against power disturbances?

  1. We offer many different electrical services to ensure power quality in your business or home however; proper surge protection coordination can prevent damage from most power surges.
  2. There are two types of Ac surge protective devices: The first type of surge protective device is the service entrance surge protective device. This device mounts at or near the incoming electrical service. The second type is the point-of-use surge protective device. It utilized at the Ac electrical component that requires protection and includes the type of surge protective devices that plugs into a wall outlet.
  3. Telephone lines, cable TV (CATV) coaxial cables, closed circuit TV (CCTV) cables, satellite TV (SATV) cables, antenna coaxial cables, local area network (LAN) cables wide area network (WAN) cables, gate control leads and motor control leads should all be protected from power surges by a surge protective device.

Surge Protection Terminology

Surge Protective Devices over the years have used many different names and phrases for surge protectors, surge suppressors, lightning arrestors, transient voltage surge suppressors (TVSS), or secondary surge arresters. Underwriters Lab standard UL 1449 third edition defined any type of surge protective device as an SPD. However; a building owner if they understand the terminology can help make the decision easier.

All surge protective devices provide some type of protection against power surges. UL 1449 third edition standardize the terminology used for surge protective devices so that when shopping for a SPD a person can understand and compare the terminology. A customer can now compare not only price but the type or quality of protection they desire for their electrical equipment. UL1449 newest revision is UL 1449 fourth edition.

Secondary Surge Arrester: These devices are designed to go on the inside or outside of the house. If tested, they are tested according to the recommendations of the Institute of Electrical and Electronics Engineers (IEEE) standard C62.11, Metal Oxide Surge Arresters for Alternating Current Power Circuits, with a 10,000-volt, 5,000-amp power surge. IEEE C62.11 is not a test and does not assign a clamping voltage for secondary surge arresters. This makes it difficult to compare the capabilities of one product to the next.

These devices include the meter-mount surge protectors and the plug-on surge protectors that snap into the electrical panel.

Ac Surge Suppression Devices: Are generally designed to go on the inside of the house. If tested, they are tested according to the newest Underwriters Laboratory (UL) standard UL 1449 Fourth Edition with a 6,000-volt, 500-amp power surge. UL 1449 assigns a Voltage Protection Rating (VPR) to the SPD which can be used for comparison from one product to the next.

These devices include the point-of-use surge protectors and service entrance surge protectors mounted on the electrical panel.

Clamping Voltage: SPDs should have a clamping voltage specified. Clamping voltage is the voltage at which a surge protector begins to work by redirecting the power surge to ground. The lower the clamping voltage of the surge protector, the lower it will reduce the power surge voltage.

UL 1449 4th Edition: This is a test standard that was developed by UL in conjunction with industry to certify product ratings and ensure proper markings on SPD products. Through this test, the Voltage Protection Rating (VPR) is determined.

IEEE C62.11: This standard, written by the Institute of Electrical and Electronics Engineers, has recommendations on how to test secondary surge arresters. [IEEE C62.11: Standard for Metal-Oxide Surge Arresters for AC Power Circuits (>1 kV)]

Voltage Protection Voltage: This is the residual surge voltage that passes through a surge protector after the protector has "clamped" in response to the power surge.

The clamping voltage does not determine the Voltage Protection Rating for all power surges. For example, if a point-of-use surge protection device has a clamping voltage of 330-volts - that means the device will let-through no more than 330-volts if the power surge is exactly the size, shape and duration of the 6,000-volt surge required in the test standard, UL 1449.

If the same device (with a 330-volt clamping) is subjected to a power surge with a higher energy level (voltage, amperage, or duration), the Voltage Protection Rating will be above 330-volts.

Metal Oxide Varistors (MOVs): MOVs are a common technology (not the only type) and are at the heart of the surge protectors (SPD’s) ability to protect against power surges. Generally, the larger they are and the more there are equates to better protection and a more durable, longer-lasting surge protection device.

MOVs redirect the electrical current in the event of a power surge. How an MOV works is easier to understand if you think of it as a water spigot. Under normal conditions, without power surges, the MOV is a "closed valve" allowing current to flow in the electrical circuit and not through the MOV.

If there is a power surge, the MOV clamps the voltage by redirecting the electrical current (opening the valve) from the electrical circuit into the grounding system until the surge voltage drops below the clamping voltage of the protective device. When the power surge is over, the MOV returns to the "closed-valve" position.

During the power surge, all of the excess energy of the surge is diverted by the MOV, causing it to get hot. The temperature of an MOV disc can vary from room temperature to several hundred degrees after a power surge has been redirected.

The higher the voltage of the power surge, and the longer it lasts, the more energy that must be diverted and the hotter the MOV becomes. MOVs are sacrificial, meaning they will divert a finite number of power surges until they are eventually destroyed. They may reach end-of-life after only a single large surge or over several years from several smaller surges.

Thermal Fuse Protection: Because MOVs heat up when handling a power surge, there is a potential for the surge protection device or material surrounding the surge protection device to catch fire. The UL 1449 tests the fire safety of the TVSS surge protection devices by requiring severe overvoltage tests, causing the MOVs to fail.

The surge protection device passes if it does not create a fire or electrocution hazard. This is commonly accomplished by the use of thermal fuse protection. Under the previous version of UL 1449 surge conditions could cause the surge protector to overheat and catch fire. The thermal fuse reduces that risk.

L-N, L-G, & N-G Protection (MODES of Protection): The electrical system in your home is typically a three-wire system. The wires are the ground, line (hot), and neutral. A power surge can exist across any of these wires. The surge protection should protect against surges coming through any of these wires. When a surge protection device indicates the following, you know all wires are protected: Line to Neutral (L-N), Line to Ground (L-G), and Neutral to Ground (N-G). Secondary surge arresters installed at the service entrance have only Line to Neutral (L-N) protection because there is no ground wire in the locations where they are installed.

For the typical building owner, SPGS recommends an Ac Surge Protective Device (SPD), as well as Telco, Data and CATV or Satellite protection as equipped in the home. AC Main Service Entrance surge protective device that protects all electrical equipment in the house from power surges and lightning strikes. Telco cable pair protection has either normal telephone line protection or data line protection also known as a DSL line. Coaxial cable protection is needed for CATV protection or optional Satellite TV protection.

For the building owner that prefer modular protection SPGS recommends selecting individual modular Surge Protective Devices that have more selectable protective ratings for AC Main Service Entrance, Telco cable pair protection, data line protection CATV protection or Satellite TV protection.

Susceptible appliances can be identified because many times they have electronic push buttons, electronic clocks, or digital displays. If the appliance has other wires connected to it (such as telephone lines, cable TV cable, antenna cable, or satellite dish cable), those wires or cables must run through the point-of-use surge protection device as well to provide protection on all lines.

For home office or special medical needs, additional and different protection from other types of electrical power interruptions may be appropriate as well.

There is no surge protection device or system that can protect against all power surges. A direct lightning strike to the house's electrical system may be too great for the surge protector(s) to handle. The two-stage surge protection system recommended in this article should protect against most of the power surges.

Why is it Better to Have a Two-Tiered Surge Protection System?

By combining a service entrance surge protector with point-of-use surge protectors’ located at all sensitive electronics, a better protection system is created.

  1. Using a service entrance surge protection device provides protection for the entire electrical system. They protect things such as motors, lights, outlets, light switches, and all the other "hard wired" items in the house that do not plug into an electrical outlet and can't be connected to a point-of-use surge protection device.
  2. If the power surge is created by a lightning strike or power fluctuation on the utility lines, the service entrance surge protection device can reduce the power surge to a lower level before it gets to the point-of-use surge protection device. This helps:
    1. Prevent damage to the point-of-use surge protection devices from surges too strong for them to handle
    2. Reduce the level of the power surge at the appliance being protected. (The power surge's energy level is reduced at the service entrance device and again at the point-of-use device.)
  3. Service entrance surge protection devices do not eliminate the need for point-of-use surge protection devices.
    1. The power surge may not be generated on the incoming utility lines. For example, lightning may hit an outside light fixture creating a power surge on the circuit powering the light. If there are outlets on the same circuit as the outside light fixture, any electronics plugged into those outlets will be better protected if a point-of-use surge protection device is used.
    2. The point-of-use surge protection devices help protect appliances against surges that are generated within the home.
    3. Good quality point-of-use surge protection devices have the ability to reduce power surges to lower levels than typical service entrance surge protection devices.

Examples of Service Entrance Surge Protective Devices

There are service entrance surge protective devices that mount in or on your main electrical panel, or at the base of the electric meter. Several examples are shown in this article. Only one service entrance surge protection device is needed if it protects all incoming lines, including electrical, telephone, and cable TV lines. As an alternative, separate devices can be installed on each incoming line.

  1. Service Entrance Surge Protection at the Main Electrical Panel: (Both of these devices will require additional surge protection devices on the incoming telephone and cable TV lines because neither provide protection of those lines as an integral part of the device.)
  2. Service Entrance Surge Protection at the Electric Meter: (This device requires additional protection devices on the telephone and cable TV lines.)
  3. Point-of-Use Surge Protection Devices: There are also several types of point-of-use surge protection devices. Point-of-use surge protection devices (plug-in type): You may be familiar with the plug-in type surge protectors. They look like plug strips, having several plug-in locations on one device. A regular plug strip, unless it specifically says so, does not provide surge protection. Be careful when buying such items to make sure that you are getting the surge protection you need.
  4. Surge protection electrical outlets: Special electrical outlets contain surge protection in those places that you don't have room for or don't want a plug-in type surge protector, such as at a countertop microwave oven.

Shopping Tips

Service Entrance Surge Protection

Service entrance surge protection devices will either be a SPD or a secondary surge arrester. It is not possible to compare the capabilities of a SPD to a secondary surge arrester because they are tested differently. Insurance companies do not recommending one type over another. We will offer suggested specs for both.

  1. Tested Product: It is very important that the device has been tested. Look for a secondary surge arrester that is tested according to the recommendations of IEEE C62.11 or a TVSS that has been tested in accordance with UL 1449, 2nd Edition.
  2. Fuse Protection: Look for a SPD device that has thermal fuse protection. If the device is a secondary surge arrester, make sure it is fused.
  3. Voltage Protection Rating (VPR): SPD service entrance surge protectors will typically have a Voltage Protection (VPR) greater than 500 volts.

The lower the Voltage Protection Rating (VPR) the better the protection.

Service entrance surge protection devices classified as secondary surge arresters will not have a Voltage Protection Rating (VPR) because they are not tested to UL 1449. Purchase a device that is tested according to the recommendations of IEEE C62.11. Talk with the manufacturer about the device's capabilities. Since there is no standardized test method for secondary surge arresters, each manufacturer may test their product differently, making a performance comparison between products difficult or impossible.

  1. Surge Protection on All Electrical Wires (All Mode Protection): Verify the surge protection is on all electrical wires. SPD devices should indicate protection for Line to Neutral (L-N), Line to Ground (L-G), and Neutral to Ground (N-G). Secondary surge arresters mounted on the utility side of the electrical panel will have only L-N protection.
  2. Telephone and Cable TV Protection: Install surge protection on the incoming telephone and cable TV lines as well as the electrical line. It is possible to accomplish this with one surge protection device or separate surge protection devices at each utility line.
  3. Working Indicator Light: Most all service entrance surge protection devices have indicator lights that will signify if there are any problems with the protection. Be sure the device you buy has this feature. Most of these devices, if the surge protection capabilities are destroyed, will still conduct electricity. The indicator lights are a way to check to make sure the device is still protecting.
  4. Good Warranty: Find an established manufacturer with a good reputation. Their warranty should cover any damage to the equipment that is protected by their product.
  5. Joule Rating: The joule rating indicates how much energy a surge protection device can handle. Because testing to determine joule ratings has not yet been standardized, the joule rating cannot currently be used for comparing products.

Point-of-Use Surge Protectors

  1. Tested Product: These types of surge protectors all fall under the category of SPD’s. Purchase only devices that have been tested to UL 1449, 4th Edition.
  2. Thermal Fuse Protection: Look for a device that has thermal fuse protection.
  3. Voltage Protection Rating (VPR): Purchase SPD with a listed Voltage Protection Rating (VPR) of 300 if possible, the best rating given under UL 1449. It will be difficult to find SPD’s that plug into outlets and have a Voltage Protection Rating of 300-volts.
  4. Voltage Protection Ratings: Is found on the surge protector's rating plate (see below)
  5. Surge Protection on All Electrical Wires(All Mode): Make sure the surge protection is on all electrical wires. The device should indicate protection for Line to Neutral (L-N), Line to Ground (L-G), and Neutral to Ground (N-G). A voltage Protection Rating (VPR) should be listed for all modes of protection.
  6. Fax/Modem and Coax Protection: When purchasing a point-of-use type surge protector for a computer, VCR, or TV, look for a device with telephone and coax cable jacks for protection of those lines if the item being protected has those types of hookups. Remember, power surges can enter through the electrical, telephone, or coax lines.
  7. Loss of Power After Catastrophic Failure Feature: Look for point-of-use surge protection devices that no longer conduct electricity once the capacity to protect against power surges has been lost. Surge protection devices are designed to sacrifice themselves for the equipment they are used to protect. Once they have had too many surges, they no longer protect. However, if they still conduct electricity, a building owner may never be aware the device has lost its ability to protect. With this feature, once the protection has been destroyed by a power surge, the surge protector outlets will no longer be powered.
  8. Ground Wire Indicator Light: A convenient feature to have is a plug-in type surge protector that has a light that will indicate whether or not the outlet it is being plugged into is properly grounded. Grounding is required for the surge protection device to work most effectively.
  9. Good Warranty: Find an established manufacturer with a good reputation. Their warranty should cover any damage to the equipment that is connected through their surge protection device.
  10. Joule Rating: The joule rating indicates how much energy a surge protection device can handle. Because testing to determine joule ratings has not yet been standardized, the joule rating cannot currently be used for comparing products.

Proper Grounding Imperative

Without proper grounding a surge protection device's ability to protect is greatly diminished or impeded. For more information about this, read the article, The Importance of Proper Grounding. This is important information to have if you are designing or building a new home or remodeling.

Do not connect a plug-in type point-of-use surge protection device to an electrical outlet by using a two-prong extension cord. The surge protection device's ability to protect against power surges will be diminished. And many surge protection device warranties will not cover any damage if this is done.

Planning of Electrical Circuits

If you are building a new home or remodeling, properly organizing the electrical circuits can reduce exposure of power surges to sensitive equipment. Don't place wall outlets that are going to be used for computers, TVs, microwaves, and stereos on the same circuits powering large appliances with motors, such as refrigerators or freezers.


Service entrance surge protection at the main electrical panel or electric meter requires installation by a qualified electrician. Installing it at the electric meter also requires the approval of the utility company. Service entrance surge protection (for the electrical system only) can also be accomplished with plug-on devices that snap into the electrical panel just like a circuit breaker.

Costs for service entrance surge protection can start at $80 (material and labor) for the plug-on type devices inside the electrical panel. For those mounted on the outside of the main electrical panel or installed at the electrical meter, the range is $150 to $500 or more (material and labor).

Costs can range from $20 to over $100 for better quality point-of-use type surge protection devices that plug into electrical outlets.

Surge protection outlets, which require the services of a qualified electrician, cost around $40 (material only) as compared with a typical electrical outlet that costs around $2 to $4 (material only).


Why hasn't damage from power surges been a problem before now? Power surges have always existed. Appliances and products going into our homes, however, have changed.

Sensitive electronic circuitry is appearing in more and more appliances in the typical American home. Also, the amount of electronic equipment in the home is increasing -- DVD players, satellite TV, video games, stereo systems, and personal computers are becoming commonplace.

The electronic circuitry is getting more dense and compact, making the circuitry more vulnerable to damage from power surges. Equipment and appliances are becoming more interconnected with one another and more connections will be made with phone lines and coax cable lines. Electric utility companies are deregulating at a time when there will be more demand for electrical power. All this increases the chances of damage from power surges.

The cost and number of electronics and smart appliances in the home will continue to increase. Combining this with the potential increase in power surges means damage from power surges will cost us more in the future.

The cost is not borne solely by insurance companies. The consumer loses also. Most power surges do not originate from lightning strikes. Damage from power surges created by the utility company or generated within the home is either not covered or has coverage limitations in most insurance policies.

Even for damage caused by lightning, coverage is often limited (depending on type of insurance coverage) because of the depreciation on the piece of equipment and the deductible. Because of the potential financial loss to the building owner, a good surge protection plan should be considered, no matter where you live in the country.

Understanding the problem and knowing what options are available to you puts you ahead in the protection of your property.

Always consult an experienced contractor or other expert to determine the best application of these ideas or products in your home.

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