The Surge Protection Device (SPD) should always be installed as close as physically possible to the equipment to be protected, since cabling impedance can add as much as 100V per foot to the voltage suppression level.
Another important factor is the grounding system, as the majority of transient events occur in the common mode. A faulty or high impedance grounding system can render a surge protection system ineffective. Most grounding installations of critical equipment call for the grounding system impedance to be 5 ohms or less.
We must also address the vital consideration of Equipment Criticality. Although assessments from the consulting engineer and electrical contractor are helpful, only the end user can determine the true cost of damaged and/or non-functioning equipment. Based on the importance of the protected equipment, the perceived susceptibility of the power distribution system may increase. Critical equipment may require an evaluation at a higher susceptibility due to the requirement of little or no down time. In these locations, normal selections based on exposure levels and equipment location categories may be increased due to the equipment being protected. Some examples of this type of equipment are Data Processing, Medical, and Point of Use.
Although not always considered a part of the installation environment, Features and Benefits are an important aspect of the application process. Along with exposure levels and equipment location categories, features and benefits may drive the selection of a particular model or system. Features or benefits promoting serviceability, performance, inter-connectability and available system information may influence the requirement of a certain series or product selection. The installation environment may dictate certain features, e.g., an installation in a high exposure environment with extremely critical equipment may require a disconnect switch as well as field replaceable suppression elements. This provides the means to be back online quickly in the event of a suppression component failure.
The “Site Shield 3g Risk Assessment Guide” can be used to coordinate and select the appropriate SPD to be installed in a particular application.
Download a Site Shield 3g Risk Assessment Spreadsheet (pdf) or contact THOR SYSTEMS, INC. to perform an on-site evaluation to determine the best solution for your environment.
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