Design and Technical Manual

6. SYSTEM DESIGN
REFRIGERANT CONCENTRATION PRECAUTIONS11.
The system designer and installer are to ensure that the system adheres to all local regulations
regarding refrigerant leakage.
INTRODUCTION11-1.
Designing HFI systems requires special attention to codes and standards relating to
Refrigeration Concentration Limit (RCL). The RCL is intended to “reduce the risks of acute
toxicity, asphyxiation and ammability hazards in normally occupied, enclosed spaces”.
Because R-410A in neither toxic nor ammable; the primary safety concern is asphyxiation
due to oxygen deprivation.
Concentration limit
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The purpose of the concentration limit is to protect occupants in the unlikely event that the
entire refrigerant system leaks into the smallest room served by the system. To calculate the
potential refrigerant concentration, divide the total refrigerant in the system by the volume of
the smallest space served by the system.
The Concentration Limit for R-410A : 25lbs./1,000 ft³ (0.40kg/m³)*.
*Based on ASHRAE 34-2007 and IMC-2009
Outdoor unit
Indoor units
Branch box 1 Branch box 2
Flow of
refrigerant
Entire refrigerant charge in
the system leaks into the
smallest room.
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SYSTEM DESIGN SYSTEM DESIGN