REFRIGERANT GAS LEAK MONITORS
A Guide For Design/Spec Engineers
I. REFRIGERANT LEAK DETECTION (RLD) MONITORING SYSTEM
Analyzer shall be an active air-sampling microprocessor-based monitoring system that employ infrared (IR) sensor Technology. It shall accurately provide sensing down to one part per million (ppm); shall be compound specific and/or capable of monitoring multiple refrigerant compounds at multiple zones. The RLD is to be calibrated to detect a specified refrigerant(s).
II. SAMPLE AIR TUBING:
A. Sample air will be picked up from a vacuum pump located within the refrigerant gas monitoring panel.
B. The refrigerant gas leak monitor Control Manufacturer shall make available the necessary sample air piping for all indicating, controlling and controlled devices. Sample air piping throughout the system shall be "FR" (fire retardant) multiple virgin polyethylene tubing with integral anti-oxidant, verman-proof inhibitor unless otherwise specified herein.
C. The sample air piping shall be installed in a neat and workmanlike manner and shall be properly supported using straps, clips or hangers, as approved. Air piping shall be supported on not over 6 ft. centers on vertical runs, and 4 ft. centers on horizontal runs. Pipes shall not be hidden within duct insulation, run over access panels, or supported from pipes or conduits.
D. In exposed, unfinished areas such as mechanical rooms, polyethylene tubing shall be run in a trough or EMT with compression fittings. All tubing in concealed, accessible areas shall be sheathed. In exposed, finished areas tubing shall be run covered or in wiremold. Runs under 30" from (trough or EMT; sheathed bundle) of single-strand tubing may be polyethylene tubing.
F. Non-metallic tubing shall meet stress-crack test ASTM 1)1 693-60T. Tubing shall be self-extinguishing under ASTM-D635 flammability est. Where exposed, this tubing shall be run within adequately supported rigid metallic raceway, electrical tubing or duct, or in multitube bundles.
III. REFRIGERANT LEAK DETECTOR (RLD) STRUCTURE:
A The System shall be of design consisting of a refrigerant gas monitor and other equipment specified or needed to complete the system. Sampling shall be continuous with response time ranges from 5 to 90 seconds, depending on the sample tube length and gas concentration per area measured.
B The basic elements of the RLD shall be built up of only standard components kept in inventory by the RLD supplier. The components shall not require customizing other than setting jumpers and switches, adding firmware modules or software programming to perform required functions.
C. All system components shall be fault tolerant.
1 Provide static, transient, and short circuit protection on all inputs arid outputs. Communication lines shall be protected against incorrect wiring, static transients and induced magnetic interference. Bus connected devices shall be a.c. coupled or equivalent so that any single device failure will not disrupt or halt bus communication.
IV. SEQUENCING OF CONTROL OPERATION:
A. REFRIGERANT ROOM VENTILATION SYSTEM (RRVT).
Provides monitoring and alarm of refrigerant level in the Mechanical Equipment Room (MER). The PLC will monitor the unit for failure alarm.
Theory of Operation
The refrigerant monitoring system (RMS) shall monitor the refrigerant levels up to sixteen (16) gases and points within the MER. On system alarm, the RMS control panel will automatically initiate emergency ventilation procedures. RMS will be monitored by the PLC for central alarm and interlocked to the ventilation system for 100% OA emergency ventilation. The BAS system will be interlocked to shut down all refrigerant based equipment within the MER. The RMS will monitor HCFC-134a concentration. A remote display of room refrigerant concentration shall be provided in the main control room to provide remote indication of purged conditions There will be audio/visual alarms provided at all break glass switch locations (entrance doors) to the MER. Alarming of refrigerant level will be:
At TLV the emergency ventilation routine should be initiated contacts in the break glass system will be activated and operators should be warned that respiratory protection is recommended but not required.
At STEL the procedure is the same as TLV except that the operators shall be warned that respiratory protection is required.
At EEL the procedure is the same as TLV except that all operators shall be required to leave the space immediately.
The PLC will monitor the panel for fault indication.
The refrigerant monitor shall provide an analog output [ 0-10 v DC) that corresponds to the level of refrigerant detected by the monitor. This signal shall be connected to the BAS where it will be used to generate an electronic log of the refrigerant level in MER-1. Any increase in the level shall trigger an informational diagnostic indicating that the refrigeration system should be checked for leaks.
Supply and exhaust air for the MER shall serve no other portion of the building. Air discharged from the MER shall be ducted to the outdoors as indicated on design drawings and shall not cause inconvenience or danger. Sufficient inlet/make-up air shall be provided through existing wall openings located between the MER and adjacent fan room to replace air being exhausted.
Ventilation inlets and outlets for the MER shall be placed to provide a fresh air sweep across the refrigeration equipment. Equipment spacing and positioning shall be coordinated with ventilation inlets and outlets to avoid areas of stagnation around the refrigeration equipment.
1. The start of the unit will be by any one of the following items:
a A local line voltage thermostat (TSH) will start the unit. When room
temperature exceeds 850F the fan will be on. The deadband of the
thermostat will provide for deactivation at 80~F.
b. The refrigerant management system will automatically start the unit
on detection of a refrigerant leak
c. A local push-button will automatically start the unit manually.
2. When the RRVT is activated a solenoid valve will provide ur to open the damper in the exhaust ductwork and outside air louvers in the wall.
Click here to download a table of recommended factory settings: