Description

The module monitors a length of Digital Linear Heat Detecting Cable (LHDC) for both Fire condition, and Fault status (open circuit).

The unit is designed such that it may be configured to operate in a `two wire' mode that emulates the operation of conventional smoke & heat detectors. The unit may therefore be directly interfaced with fire control panels by connection to fire zone trigger circuits or addressable interface modules.

The unit has a 3½ digit LCD which activates on fire condition and displays the distance into the zone that the alarm has occurred. Digital LHDC may be employed in lengths up to 2km (1999m). The unit has an adjustment to accommodate interposing cables.

Signalling of fire and fault status by means of volt free contacts may also be realised when a separate supply is employed.

The DIN rail modular form of the unit enables it to be provided in a variety of discrete housings.

A 4 to 20 mA instrumentation current loop out put is provided for connection to PLCs etc.

• Operable from two wire fire panel Trigger Circuits. Line / Low Power.



• Display of Alarm Location - Distance in metres.



• 4 to 20 mA instrumentation current loop output.



• LHDC Hazardous Area use by means of Intrinsically Safe Zener Barrier.



• Fault monitoring of LHDC for open circuit conditions.



• LED indication of Fire, Fault & Supply status.



• Can be interfaced with and powered from addressable loop.



• Test & Reset push-buttons.



• Volt free contact outputs for Fire & Fault conditions - Selectable option.



• DIN Rail Mounting.

Principles

The unit is operated in conjunction with a length of Digital Line Heat Detector Cable (LHDC) and an `end of line' (EOL) terminator. The LHDC is a twisted pair twin core cable. When the trigger temperature of the LHDC is reached these cores connect and a Fire alarm is registered. The LDM-519-DDL unit automatically determines the distance to the point of operation and displays this by means of an LCD.
The current loop output provides an analogue of the ’distance’.This o/p is 0mA when normal, and scaled 4mA = 0m / 20mA = 2000m on LHDC operation.

Reference should be made to the (separate) data sheet on the Line Heat Detectors for specification of their performance.

There are three principle modes of supply & signalling operation :-

Figure 1 shows a typical minimum system where a discrete 24 Vdc supply is employed. The repeat contacts may be employed to signal an alarm panel and/or initiate control systems.

Figure 2 shows a simple configuration with the unit directly connected to a fire panel trigger circuit.

Figure 3 shows the configuration when an integral LOOP interface module is fitted.

Module Arrangement

Enclosures

The unit can be mounted in a variety of enclosures. For the example shown :-
Rating :- IP 66
Lid :- Clear Transparent
Material :- Polycarbonate
Base :- Grey RAL 7035
Material :- Polycarbonate
Optional Escutcheon
Versions available with integral address loop modules.

Operational Specification

Display:
  Four digit LDC : 0 to 1999 m range
  Character height : 8.5 mm
  Unit Location accuracy : +/- 1% (+/- 1 digit)
  LHDC Tolerance : +/- 3%
  Lock time : 3s

Voltage:
  14-30 Vdc  (2 wire Mode)
  20-30 Vdc (Relay Mode)
  >10 Vdc - Latched Fire
  < 6 Vdc - Reset

Current-Normal:
  < 1.5 mA  (2 wire mode @ 17V)  -  Plus user defined monitoring current - Resistor at terminals 13 & 14.
  < 11 mA (with fault relay enabled)

Current-Fire:
  < 12 mA (2 wire mode)  -  Plus user defined trigger load - Set by resistor at terminals 11 & 12.
  < 22 mA (with fire relay enabled)  -  Plus 4/20mA loop current - If employed.
  < 29 mA (with both relays enabled)  -  Plus 4/20mA loop current - If employed.

Current-Fault:
   < 700 µA

Relay Contacts 1 A @ 24 Vdc / 120 Vac

Direct Powered Configuration - Relay Mode

In this mode both fire & fault relays are enabled by links at 7/8 & 9/10. The fault relay is energised in normal condition. A 24 Vdc power supply is required as the fault relay coil current requirement is greater than can be obtained from most trigger circuits whist maintaining the required voltage. Both fire & fault relays have twin contacts enabling both local control and repeat signalling. The 4 to 20 mA analogue current loop output may be employed to signal to remote display equipment.

Line Powered Configuration - Two Wire Mode

In this mode the relays are disabled and the unit's quiescent current is very low. By connection of appropriate value resistors at 11/12 and 13/14 the unit replicates the characteristics of smoke and heat detectors and may be directly connected to, and powered from, most fire system trigger circuits.

The resistor at 13/14 is presented to the trigger circuit when the unit is in normal condition. Should an LHDC open circuit fault or low voltage condition occur the resistor is "switched out" and the unit draws less than 700 uA from the trigger circuit. Systems employing end of line zeners should operate satisfactorily with the zener connected at 13/14 instead of a resistor. It may be necessary to use a lower value device than normal as there is a 0.7-1.0 V loss through the unit.

The resistor at 11/12 is presented to the trigger circuit on fire detection. The value should be chosen taking into account the trigger circuit characteristic, the increased unit current in alarm, and the voltage requirements.




For Installation & Operation including IS Barriers refer to LDM-519-DDL Data-sheet
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