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Gas Monitoring System

SHERLOCK 102 Refrigerant Gas Monitoring System


Monitoring Panel


The Sherlock 102 Control Module is a hard wired, permanently mounted electronic control panel that is capable of monitoring the analog output signal of one Sherlock Refrigerant Gas Sensors or Oxygen Depletion Sensors. The Control Module will activate four Form C SPDT relay contacts based upon the programmed alarm setpoints of each sensor. The relays are referred to as K1, K2 for the first alarm level and K3, K4 for the second alarm level. There is optional zone isolation alarm relay (K5 & K6) for each Sensor. The Control Module can be located in the area to be monitored, or in a separate location, typically outside of the monitored room.

Monitoring Points


Each monitoring point consists of an analog signal generating sensor connected to the control module via discrete, three conductor cable. Each sensor can be mounted up to 1000 feet away in locations where leaked refrigerant is likely to concentrate.


The Sherlock gas sensors are available in three varieties:


  • Ceramic Metal Oxide Semiconductor (CMOS) or Solid State Sensor
  • Non-Dispersive, Pyro-Electric Infrared Sensor.
  • Oxygen Depletion Electro-chemical Sensor.


Alarm Level Settings


The Sherlock 102 allows you to set a unique Level 1 Alarm Setpoint and delay and Level 2 Alarm Setpoint and delay for each individual sensor. When an Alarm Setpoint is exceeded, after the user set delay, corresponding alarm relays are activated Each Alarm Setpoint has a programmable Alarm Delay, 1 to 120 minutes. Sensor readings are required to exceed an Alarm Setpoint for the programmed amount of time before the control activates the corresponding alarm relay contacts. For example, if the Alarm Setpoint is 200 and the Alarm Delay is five minutes, the control will enter an alarm condition only if the sensor detects a level of 200 or higher for more than five minutes.


Alarm Indication


All alarms are logged to indicate which sensor went in and out of any of the two alarm levels, the time and date of the alarm. The alarm log stores the last 10 alarms. When a sensor is in alarm, a red alarm light on the front panel will flash and the on-board beeper will sound and the display will show the activated alarm level.


Alarm Relay Contacts


The Sherlock 102 provides two fused SPDT (Single Pole Double Throw) relay outputs for each alarm level that switch positions in the event of an alarm condition. Level 1 Alarm activates K1 and K2 relays. Level 2 Alarm activates K3 and K4 relays. Level 2 alarm on each individual sensor can be disabled. One alarm relay on each level (K2/K4) can be silenced (returned to non-alarm state) when the ALARM CLEAR button on the front panel is pushed. The other alarm relays will remain active until the alarm condition is cleared. The Sherlock 102 can be programmed so that the alarm is cleared automatically when the air is cleared below the alarm setpoint (UNLATCHED) The relays can also be programmed so the alarm is latched "ON" until the alarm is manually reset. The relays can be configured so the relays are "Energized to Alarm" (where the C-NC contacts open on alarm) or "De-Energized to Alarm" (where the relay is energized during normal operations and the C-NC contacts close on alarm).


Systems Sensor Opening Monitoring


The Sherlock 102 constantly monitors the wiring to the sensors. Should any of the activated sensor wires be cut or disconnected, "SENSOR ALARM" will appear on the SHERLOCK display, the K1 and K2 relays will be activated and the condition is logged./font>


Setback Alarm Settings


In some locations the sensor may be expected to function in two different environments. For example, the sensor may have to perform in still air (i.e. with the exhaust fan off) and in moving air ( i.e. with the exhaust fan on), or the sensor may be used in a location where changes in air quality, perhaps caused by the use of propane powered floor buffers, elevates the sensor readings. The Sherlock 102 provides a feature called SETBACK to accommodate alternate environments under which the sensor would operate. SETBACK provides a second ALARM SETPOINT and a second ALARM DELAY enabling the sensor to perform in this second environment. The Sherlock 102 switches to the second set of parameters when a dry contact (i.e. air flow switch, sail switch or timer switch) closes or on a daily time schedule.


Clark Johnson Company, Inc.       2016