System Design Considerations

Due to the wide variation in equipment room layouts, each situation must be considered individually. The following information is a general guideline for CMOS and Infrared systems. Remote Notification
ASHRAE 15-2004 requires that audible and visual alarms be present inside the mechanical room as well as outside each entrance to the mechanical room. System compatible remote strobe lights and audible alarms are available to meet these requirements. The Haloguard Remote Display panel is also available to provide gas concentration and diagnostic information, visual and audible alarms outside the mechanical room. All Haloguard Monitors can also communicate to Building Management Systems.

Number of Sensors/Sample Points
How many sensors do you need? A good rule of thumb is that there should be one sensor or sample point for each 20,000-30,000 cubic feet of room volume, or no less than one sensor/sampling point fewer than the total number of chillers, whichever is less; provided that there is one sensor for each refrigerant safety group used in the room.

Location of Sensors/Sample Points
The ability of a monitor to measure the refrigerant concentration is dependent on the location of the sensing point. The sensing point may be remotely located up to several hundred feet from the controller. The controller and sensor/sensing point should be rigidly mounted indoors. The controller should be located in an area where the display can be viewed from most parts of the room and where it can be easily accessed for occasional calibration and service. The sensor/sampling point location should be approximately 18 inches above the floor, in an area where refrigerant vapors are most likely to accumulate. Sensors/sampling points should be located in low-lying areas for occupant safety or near each potential leak source for if refrigerant conservation is a high priority.

Airflow Patterns
If there is a continuous draft in the room, a sensor/sampling point should be located downstream from the last potential leak source. Airflow patterns can also cause areas of the room to become stagnant and allow refrigerant vapors to accumulate. The sensor/sampling point location should be between the refrigerant leak source (chiller) and the ventilation exhaust. Smoke tubes can be useful in determining the ventilation patterns.

Equipment Configuration
The equipment arrangement in the room can also affect the proper place to sample or locate a sensor. As a general guideline, if there is one chiller in the room, sample at the perimeter of the unit. For two chillers, sample between them. For three chillers, sample between each pair of chillers. (Note: we recommend using 2 or more points of monitoring). With four or more chillers, multiple monitors or a single monitor with a multipoint sampling system should be used.

Activities in the Room
The expected activity in the room, should be taken into account when choosing sampling locations. Some activities may require locating the sensing point above or below the 12 to 18 inch height. Traffic patterns can also affect airflow. If unsure as to location, contact Thermal Gas Systems, Inc. to discuss.

All Haloguard Monitors Are Built To Order For The Least Cost Based On:

Monitoring Priorities:

  • Maximum refrigerant conservation
  • Occupant safety
  • Regulatory Compliance

Mechanical Room:

  • Size & layout
  • Number of entrances
  • Airflow patterns


  • How many?
  • What type?

Gas of Interest:

  • Virtually all refrigerants are supported
  • Number and Types of gases
  • Gas Combinations
  • Oxygen depletion monitoring is also available

Output Requirements:

  • Operate Local Devices – Relay contacts
  • Analog Output
  • Serial Communication
  • Data logging

Thermal Gas Systems, Inc.

11285 Elkins Rd.
Bldg. H-1
Roswell GA 30076
Tel: 770 667-3865
Fax: 770 667-3857
Toll Free: 800 896-2996

Give us a call!

Confused? Have questions?
Give us a call 800-896-2996 to discuss your specific application requirements.

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