The best way to deal with electrical surges and spikes is to divert them from entering the house in the first place. This is why the external ground system mentioned in Part II is so important. Spikes and surges look for the quickest and shortest path to ground. Industry Standards recognize that creating a tiered or layered approach to transient voltage management for your house will provide the best protection, but it’s still no guarantee. Lightning strikes and surges can appear to have their own mind when it comes to seeking ground. Following the recommendations that I have mentioned in this series of articles will assist in properly protecting you and your house.
Layered Approach to Surge Suppression
Approaching surge protection with tiers serves to create layers of filtering . ANSI and IEEE acknowledge 3 tiers, A, B and C. Each level is recognized to provide protection for a defined application. Look at the following drawing to visualize the different tiers and location of the protection device. Class C is located at the service entrance or meter, Class B serves sub-panels and points of distribution (power strips), and Class A provides protection at the source or point of use (POU).
Most whole house residential grade TVSS’s (transient voltage surge suppressor) use MOV’s (metal oxide varistors) for protection. By design, the TVSS does not absorb the fault but divert it to ground. By doing so, these faults erode the MOV’s over time. For this reason, most high quality TVSS’s include some form of “wellness” indicator or failure alarm (red or green LED lamp). Once the MOV’s are destroyed, the lamp indicator is extinguished or in some cases sets off an alarm. Studies show these MOV equipped TVSS’s can last up to 10 years. Granted, this life expectancy is directly impacted by the number of spikes and surges diverted by the MOV’s. So if you live near me in Texas, Oklahoma or places with lots of lightning, don’t count on the 10 years of life.
The IEEE recognizes three classes of surge protection and they all perform a defined task, but regardless of the class, all the surge protectors should meet these standards.
In shopping for a TVSS (aka SPD or Surge Protection Device) look for this information on the box or possibly in the fine print with the instructions.
Surge Protection Devices come in many shapes and sizes at each class allowing you different choices. If you choose to install a Class C unit, you may have to employe an electrician, otherwise you can use plug-in modules for the other two levels.
Class C Whole House TVSS Suppressors for Service Entrance Applications: Intended to be located at the incoming AC service or AC service panel. For various reasons, there are multiple types and styles for Class C residential TVSS’s. Hopefully one of these styles can be integrated into you electrical system.
Meter Base TVSS: In some municipalities the utility carrier may offer to sell or lease you this type of TVSS. Other than the fact they will probably want to charge you a monthly fee, I like the meter base style. This TVSS is placed in the circuit prior to entering the house service panel. This allows the TVSS to divert any external surge to ground prior to entering the AC Service Panel where a surge could go through the house instead of the intended ground source. I spoke with my electric provider but they did not offer this service nor would they allow me to supply my own.
Circuit Breaker Derived TVSS: With this design, the TVSS is wired into the house AC Service panel. Like most, it is equipped with MOV’s and a state of health LED lamps. These styles can be purchased for both indoor and outdoor applications (indoor model pictured). The key here is to keep the TVSS installation as close as possible to the service panel and the connection wire should be as with the short as possible (6″ or less). For my house I also re-arranged my circuit breakers in the panel to allow me to place the TVSS circuit breakers as close to the incoming mains as possible. This is just a little added work to divert the surge as soon as it enters the panel.
AC Panel Based TVSS: Similar to the circuit breaker design previously mentioned. This breaker style TVSS consumes 2 breaker positions to provide panel protection. The advantage of this type is that it connects directly to the bus terminations in the AC Service panel. The disadvantage is that it consumes two positions and you may not be able to locate one that fits your AC service panel.
Class B TVSS Suppressors for Distribution and Short Branch Circuits: As a classification the “B” type is recognized to serve electrical sub-panels and distribution, meaning a power strip with multiple outlet with a collection of devices to protect. The Class B is the most common type found in electronics, computer stores and home centers. You will have numerous to choose from. Just remember to use the criteria listed above to help with your choice. I would not use the joules rating as part of your decision making process.
Class A TVSS Point of Use Surge Protection Device for Outlet and Long Branch Circuits: As a Class A TVSS, this device can either be an individual plug-in module (as pictured) or the outlet itself. I have used both and depending on the application the outlet version can be a better choice when you have limited space, such as behind a refrigerator or Plasma TV. Additionally, I found the outlet style more difficult to obtain and more than double the cost of the plug-in style. They both include the proper operation indicator.
By this point you should recognize two major points. 1) Having proper grounding is imperative and, 2) surge suppression goes beyond point of use (POU) devices, 3) implementing a tiered approach is necessary to protect you and your household adequately.
Believe it or not…. there is still more. Next time I will discuss specific surge protection for your CATV and Telephone service.