Surge protection for your computers Print

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Lightning can kill your computers

Electrical surges originate from two major sources: lighting and power switching transients.? Both sources have their highest likelihood of occurrence during periods of inclement weather.? In our area, we experience harsh weather typically in the spring (severe thunderstorms) and winter (snow/ice).? Other sources of surges include switching circuits within the end-users systems; however, these are typically managed by the equipment manufacturer or are more prevalent in industrial settings.?

The protection of electrical/electronic devices from electrical surges cannot occur with 100% certainty while any device remains plugged in; however, precautions can be taken to limit the impact to your equipment and your business due to electrical surges.? Many pieces of equipment contain internal surge suppression circuitry; however, these should be treated as a last resort due to the cost and effort associated with internal equipment repairs.? Surge Protection Devices (SPDs) should be installed commensurate with the cost of equipment replacement and the business risks associated with equipment down-time or data corruption.? For example, in applications not involving on-line performance, protection may be desired merely to reduce the likelihood of hardware.? In other cases, such as data processing or critical medical or manufacturing processes, any interruption or upset of a process may be unacceptable.

Surge protection devices generally consist of three types for end users:

1.??????Plug-In (portable) surge protectors

2.??????Service Entrance surge protectors (whole house surge protector)

3.??????Uninterruptible Power Supply (UPS)


Plug-In surge protectors?are generally low cost and readily available; however, they are commonly confused with ?power strips?.? Power Strips simply split power from one plug into multiple plugs, allowing you to power multiple devices from a single outlet.? Surge Protectors employ various methods to limit damage to electrical/electronic equipment caused by surges.? The quality and types of protection offered by these types of surge protectors varies widely.? For less sensitive, less costly equipment, a basic surge protector may be sufficient.? As the cost, sensitivity, and criticality of the equipment increases, consider hybrid surge protectors which offer increased protection.?

Service Entrance surge protectors?are generally higher cost and are permanently installed in or near your electrical panel.? These types of surge protectors should be considered if your building/business contains a large number of sensitive devices that require protection, as it may be more cost effective than utilizing plug-in surge protectors throughout the building.? When considering a service entrance surge protector, the cost of installation by a licensed electrician should also be considered.? Additionally, it is still generally recommended to utilize coordinated plug-in surge protective devices for equipment that is especially sensitive or ciritcal.

Uninterruptible Power Supplies?are generally sold as two different types.? Some are considered static, in that they convert AC power to DC, then back to AC.? Static UPS devices provide a high level of surge protection due the isolation provided between the incoming AC power and the AC power that your equipment uses.? Others are switching UPS devices, which simply provide the incoming AC power to the end device while AC power is available, but switch over to battery power once incoming AC power is lost.? Due to the types of UPS devices sold, you may take the approach to purchase a more costly Static UPS to provide the surge protection and battery backup capability or a lower cost switching UPS in addition to surge protection in order for the back-up battery to provide you with enough time to unplug the equipment during storms or repetitive power fluctuations/outages.? Using either method is acceptable, but consideration should be made as to how much battery capacity your equipment will require. ?

Sizing your UPS:

??????????????? ???? UPS systems are designed to provide backup power to equipment after incoming AC power has been lost.? The size of the UPS that you need depends on the power that your equipment requires and the length of time you want the equipment to remain operational after AC power is lost.? A workstation load can range from 150VA to over 1000VA depending on the number of hard drives, graphics cards, memory, etc are installed; therefore it is recommended that you look on the back of your workstation to obtain its power ratings and size your UPS accordingly.


To determine the UPS size manually:

1.??????Look at the ratings for the equipment that you wish to power with a UPS and multiply the current that it draws by the voltage that it is supplied (i.e. 1.5A x 120V = 180VA)

a.???????If the equipment is only marked with Watts of power, convert the Watt rating to VA by dividing by the power factor of the equipment? (i.e. 0.9 for equipment such as servers)

2.??????Add up the calculated numbers to determine the total Volt-Ampere (VA) load that you will be placing on your UPS, then multiply the total by 1.2 to provide some margin for future expansion (e.g. 180VA x 1.2 = 216VA)

3.??????Select a UPS which is capable of providing greater than or equal to your total VA calculated.

4.??????To determine the runtime the UPS will provide after a power outage, divide the UPS ?Volt-Amp-Hour Capacity? rating by your calculated VA number in step 2 above.


To determine the UPS size automatically:

Most manufacturers provide calculators on their website which will provide a recommended UPS based on the load that you desire and the amount of runtime required after a power outage.?

When selecting a surge protector, performance ratings should be compared between those surge protectors that you are considering:?

1.??????Voltage Protection Rating (VPR): VPR is a measure of the maximum voltage a surge protector will let through to the connected equipment/devices

a.???????The lower the VPR, the better the protection.

2.??????Joule Rating: is a measure of the total amount of energy that a surge protector is capable of absorbing over time.

a.???????This rating may be an indication of the product lifespan, with a higher number being better

3.??????Response Time:? is a measure of how quickly the surge protector reacts to a surge; however, these values are difficult to measure and are typically not accurate.? For this reason, the response time ratings do not offer much in terms of comparison due to variations between methods of measurement by each manufacturer.

To ensure the consistency and safety of any surge protective devices installed, it is recommended that you verify it is listed to UL 1449, 3rd?edition.

In general, you will greatly reduce the risk of surge damage to your equipment and your company by installing any type of surge protective device.? There are hundreds of surge protective devices on the market and selection of one of them may seem like an overwhelming task; however, if you select one that is listed to UL 1449, 3rd?edition you will be adding a level of protection that did not exist without a surge protector installed.? Remember that the installation of a surge protector does not eliminate the risk of equipment damage due to electrical surges, it only reduces the likelihood of damage.? To eliminate the risk of damage caused by electrical surges, the equipment must be unplugged.

Wayne C. Unkefer, BSEE

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