Installation Manual
10.0 Best Practices
26
10.0 Best Practices
The purpose of this section is to provide recommendations regarding the proper selection and use of Surge
Protection Devices (SPDs) in CCTV systems. This document is not meant to provide guidance for SPDs
selection, placement, and use on incoming utility power. Always follow local and national electric code and
refer to licensed electricians or other trained professionals for guidance.
Surge Protection Devices are designed to prevent damage to equipment caused by transient voltages from a
number of possible sources. Due to their exposure to the environment, when planning the installation of a
CohuHD camera system, SPDs must be appropriately installed.
Depending on the exact equipment being installed, one or more SPD types must be used to properly protect
from damage caused by electrical surge. There are several types of SPDs:
AC PowerSPDs
EthernetSPDs
Power over Ethernet (PoE) SPDs
AnalogVideoSPDs
LowVoltageDC(SerialData)SPDs
Each SPD type is designed for a specific application and is only rated to work within the nominal voltage
levels of that application. To provide protection, it is critical that the SPD for your application be of the appro-
priate type and ratings. Refer to the SPD manufacturer for proper device selection for your application.
Placement of SPDs is critical. Per IEEE, NEMA, and industry guidelines, an SPD should be installed within
four feet of the equipment it is protecting. Additionally, SPDs should be installed at each end of all cables
greater than thirty feet in length. In most CCTV applications, this means that a minimum of two SPDs must be
used: one near the camera, and one in the control cabinet that provides network connectivity and power.
Proper orientation is key on many SPDs as they often have PROTECTED and UNPROTECTED terminals,
or DEVICE and LINE terminals. For a typical CCTV application, the UNPROTECTED or LINE terminals
should be used to connect the upper and lower SPDs, while the PROTECTED or DEVICE terminals should
connect to the camera and network switch (or PoE injector). An incorrectly oriented SPD will appear to func-
tion as voltage will still pass through it, however when installed backwards, the device will not provide full pro-
tection. Always verify the orientation of each SPD and contact the manufacturer for assistance.
Lastly, an SPD can only function if it is properly grounded. Unless a lower value is required to meet your local
or project-specific specifications, the grounding array that the SPD is connected to should be no more than
10
Ω
. All wiring from the ground connection of the SPD should be as short and straight as possible, and all con-
nections should be properly crimped and securely fastened.
