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IS 660:1993 is the Indian Standard (BIS) for safety code for mechanical refrigeration. IS 660 prescribes the essential safety requirements for the design, construction, installation, operation, and inspection of mechanical refrigeration systems. Engineers use this code to ensure adequate plant room ventilation, safe routing of pressure relief discharges, and proper refrigerant handling to prevent asphyxiation, toxicity, and explosion hazards.
Lays down safety requirements for the design, construction, installation, operation, and maintenance of mechanical refrigeration systems.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Ensure safety relief valves on systems containing toxic or flammable refrigerants (like Ammonia) discharge safely outdoors, above the roofline and away from fresh air intakes.
! Group 2 and Group 3 refrigerants strictly require dedicated machinery rooms with gas leak detectors, emergency isolation, and mechanical ventilation.
! Never use oxygen or combustible gases to pressurize refrigeration lines for leak testing; always use dry nitrogen.
Covers the design, construction, installation, and operation of refrigeration systems.
ISO 5149 Series (2022)ISO (International)
HighCurrent
Refrigerating systems and heat pumps — Safety and environmental requirements
Specifies safety and environmental requirements for refrigerating systems and heat pumps.
EN 378 Series (2016+A1:2020)CEN (European Union)
HighCurrent
Refrigerating systems and heat pumps - Safety and environmental requirements
European standard harmonized with ISO 5149, covering safety for persons and property.
IIAR 2-2021IIAR (US)
MediumCurrent
Standard for Safe Design of Closed-Circuit Ammonia Refrigeration Systems
Focuses specifically on ammonia refrigeration systems, which is a subset of IS 660's scope.
Key Differences
≠IS 660:1993 uses a simpler refrigerant classification (Groups 1, 2, 3) which does not account for modern low-GWP, slightly flammable refrigerants (A2L class) that are central to newer international standards like ASHRAE 15 and ISO 5149.
≠Modern international standards (ISO 5149, EN 378) explicitly integrate environmental requirements such as Global Warming Potential (GWP), leak checks, and refrigerant recovery, which are absent in IS 660 as it predates major environmental protocols.
≠Refrigerant charge limits in IS 660 are often prescriptive and based on system horsepower. ASHRAE 15 and ISO 5149 use a more sophisticated approach based on the room volume and the specific Refrigerant Concentration Limit (RCL) or toxicity/flammability limits.
≠Requirements for machinery rooms in ASHRAE 15 and EN 378 are more detailed, often mandating specific refrigerant detectors, alarms, and sometimes Oxygen Depletion Sensors (e.g., for CO2 systems), which are not specified in IS 660.
Key Similarities
≈All standards share the fundamental safety principle of classifying systems based on occupancy (e.g., Public Assembly, Residential, Institutional) to determine permissible system types and refrigerant quantities.
≈The concept of classifying refrigeration systems as 'Direct' or 'Indirect' based on how the refrigerant-containing parts are situated relative to the occupied space is a common principle across IS 660 and its international counterparts.
≈All codes mandate the use of pressure-relief devices (like relief valves or rupture discs) on pressure vessels to prevent catastrophic failure due to overpressure, including rules for their setting and discharge location.
≈The requirement for dedicated machinery rooms for large refrigerant charges is a universal safety concept, with all standards specifying enhanced construction, access control, and ventilation for these spaces.
How are refrigerants classified for safety under IS 660?+
Group 1 (safest, non-toxic/non-flammable), Group 2 (toxic and somewhat flammable like Ammonia), and Group 3 (highly flammable like Propane).
What are the requirements for refrigeration machinery rooms?+
They must have tight-fitting doors, emergency exits, and adequate natural or mechanical ventilation capable of completely changing the air in case of a leak.
How should field leak tests be performed?+
Using dry nitrogen or carbon dioxide at a pressure not less than the design pressure, verifying joints with soap solution or electronic leak detectors.