GAI-Tronics 262-001 Intrinsically-Safe Telephones - Manual (Page 2)

Pub. 42004-173G
Model 262-001 and 272-001 Intrinsically-Safe Telephones Page 2 of 12
f:\standard ioms - current release\42004 instr. manuals\42004-173g.doc
08/14
Installation
Installation Guidelines
When installing any GAI-Tronics telephone equipment, please adhere to the following guidelines to
ensure the safety of all personnel:
 NEVER install telephone wiring during a lightning storm.
 Install a UL Listed lightning arrestor on any telephone installed where the telephone or telephone
cable is at risk of being exposed to lightning strikes. The lightning arrestor must be installed as close
to the telephone as possible to maximize the protection. The lightning arrestor must not be installed
within the enclosure supplied with the telephone.
 NEVER install telephone jacks in wet locations unless the jack is specifically designed for wet
locations.
 NEVER touch uninsulated telephone wires or terminals unless the telephone line has been
disconnected at the network interface.
 USE CAUTION when installing or modifying telephone lines.
 Install UL Listed telephone line suppressor (customer-supplied) on the telephone line.
 Use silicone sealant or equivalent around and inside all conduit entries.
Wiring Requirements
Design Limits
In order to be intrinsically safe, energy and energy storage must be constrained to “safe” levels in
hazardous area apparatus. Wiring inherently has capacitance formed by a dielectric material between two
conductors. A buildup of this capacitance can form a surge of electricity, a dangerous situation in a
hazardous area.
Intrinsically-safe telephones require cabling that will limit the amount of capacitance formed. The
limitation on cable length was set by Underwriter’s Laboratory (UL) based on test results. This “worst
case” cable available was found to have a capacitance of 60 picofarads/foot. Therefore, UL set the cable
limitation at one mile, the length at which this worst-case cable capacitance level was still within
acceptable bounds.
Shielded Cable
Where multiple intrinsically-safe telephone wires are routed together, shielded cable should be used. The
use of shielded cable prevents cross-talk from occurring between multiple intrinsically-safe telephone
circuits. The shield must be grounded to an intrinsically-safe ground and connected only at the IBU.