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f one A(+) wire to many field contacts is not Systems using conventional vibrator-type horns permitted if intrinsic safety is to be preserved. and bells must use an interposing relay with a This is due to the nature of the barrier design, in suitable contact rating. If the horn or bell is to be which only a limited current, insufficient to powered from any supply other than the intrin- actuate more than one B input, is made available sically safe power supply, this relay must be an to the field wiring through each A terminal. The intrinsically safe relay, such as the Ronan Model jumpering of A terminals must be avoided, as it KV-700 or X53-1014, with its foreign voltage also defeats the current-limiting properties of the wiring segregated from that of the monitor. barrier. Each active input may be wired to a contact that 2.5 Alarm Contact Wiring either opens or closes with an alarm condition. Alarm contact wires must be routed through the Selection of the input contact type is accom- special intrinsically safe compartment in pairs plished on each module by the position of a and wired to 1A and 113, 2A and 213, 3A and 313, resistor-type jumper, identified as "NO" and and 4A and 413 accordingly. The entry for the "NC" for the normally open and normally closed alarm contact wiring is located on the left, positions, respectively. Using this terminology, a bottom of the enclosure. field contact that opens with an alarm condition The auxiliary relay contact outputs from the is termed a "normally closed" alarm input and, alarm modules should be wired from terminals conversely, the field contact that closes with an C, NO and NC to the field, routed through the alarm condition is termed a "normally open" middle entry provided on the bottom of the alarm input. enclosure. This is general-purpose wiring and 2.2 Power Source must be totally separated from the wiring to the hazardous area. The success of an intrinsically safe system depends upon a resistive barrier to limit the 2.6 Power Supply Wiring current that can be supplied from a controlled The 115 VAC source wiring must be routed (maximum) voltage. To insure that this voltage is through the entry at the right, bottom of the not exceeded, an intrinsically safe power supply enclosure and connected to the terminals (or battery) must be used and care must be identified with "H," "N" and "GROUND" taken to see that no other source of power can accordingly. enter the system. Connection of the power source to the monitor system should be checked for proper polarity and adequate wire size. - 2.3 Optional External Pushbutton Wiring 3.0 GENERAL INSTALLATION- Each pushbutton input terminal of the intrin- SERIES X76S LEAK DETECTOR sically safe monitor should be wired to one side MONITOR SYSTEM of the normally open contact of an external pushbutton, the other side being connected to The Series X76S Leak Detector Monitor System V+. This wiring must be physically isolated from is available in a wall-mounted, NEMA Type 1 any wiring not powered by the intrinsically safe enclosure. The enclosure holds the monitor modules power source. Ordinarily, this will preclude using and the approved Model X53-2000 Field Isolator the spare poles of the external pushbuttons for module, with the associated power supply, all accessi- any auxiliary function. ble through the front door. The clearly identified wire The most frequently encountered wiring error in terminations, located on the interior rear wall, provide pushbutton wiring is the use of normally closed, ease of wiring for sensor and power connection. rather than normally open, pushbutton contacts. This, of course, has the same effect as having 3.1 Field Wiring the operator pressing the pushbutton contin- The system's field wiring is shown in schematic uously. The resulting confusion is often X76C53 and must be followed explicitly. The interpreted to be a major system malfunction. system requires 115 VAC, 60 Hz, supply voltage, terminated to the appropriate terminals, to power 2.4 Optional External Horn and Bell Wiring the intrinsically safe power supply. All field wires If electronic horns are used as the system of the sensors to be monitored (e.g., tank levels) audibles, they may be directly driven by the horn that are in a Class I, Division 1 area, are to be driver outputs of the monitor. In this case, the terminated to the input of the system. Ronan Model X36 Electronic Horn should be CAUTION: The field wires from the hazardous installed with its V— terminal tied to the Al area must be connected to the system, terminal of the annunciator and its V+ terminal separated from any circuits carrying high tied to the V+ of the intrinsically safe power voltage (115 VAC) to avoid accidental connection source. z