| APPLICATIONS BULLETIN |
| Lightning Damage Prevention |
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PREVENTING LIGHTNING DAMAGE:
SURGE PROTECTION FOR ACCESS CONTROL SYSTEMS
Access Control equipment is susceptible to damage from lightning, especially when installed outdoors. Voltage spikes which travel through buried data cables, telephone lines or AC power lines can damage Access Control equipment indoors, as well.
While nothing can protect equipment from a direct lightning hit, surge protectors can help to minimize the damage caused by nearby lightning strikes. Surge protectors operate by connecting Transorbs or Varistors from data lines to ground. Surge protectors have no effect on normal circuit voltages, but can act quickly to divert large voltage spikes to ground and away from sensitive components.
Secura Key SA-Series Access Control Units are equipped with surge protection on all inputs and outputs. Smart Switches, PC’s, Printers, and Modems are designed for an indoor, office environment and do not have surge protection. However, by properly installing aftermarket surge protection devices on all inputs and outputs, these devices can also be protected from lightning damage.
Where to Install Surge Protection
• On the AC line voltage input to the PC.
• On the AC line voltage input to any transformer or DC Power Supply connected to a 26/27/28SA, Smart Switch or Modem.
• On RS-232 data lines connecting a Smart Switch to 27/28SA Units, to another Smart Switch, or to a PC, Printer or Modem.
• On RS-232 data lines from SA Units (Readers) to PC’s, Printers or Modems.
• On Telephone lines connected to Modems.
Protect Both Ends of Data Lines
Surge Protectors should be installed at both ends of RS-232 Data Lines. If this is not possible, then install one protector near the Smart Switch, Modem, Printer or PC.
Wire Distance from the Surge Protector
You must locate the protector at least three wire feet away from the device being protected. The additional wire resistance will dissipate the energy from leading edge of the spike. The wire can be coiled; a three-foot physical distance is not required.
Grounding the Surge Protector
Surge protectors must be connected to a verified good, nearby earth ground. This can be AC Power Ground, a 10' Copper Ground Stake, or Building Ground. Run 16 AWG or heavier wire as short a distance as possible, and avoid any bends in the wire.
Self-grounding RS-232 Surge Protectors
Self grounding Surge Protectors (without a ground wire or ground screw) will not work for this application. Do not use RS-232 surge protectors unless they are equipped with a separate ground wire or ground screw. Self-grounding Surge Protectors use the connector shell or Pin 1 as a ground path; however, the shell and Pin 1 are not grounded on Smart Switches and Modems.
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