What is the minimum amount of refrigerant in a piping system that requires stop valves on each inlet of each liquid receiver?

The requirement for stop valves on each inlet of each liquid receiver is set to ensure safe and effective isolation of the refrigerant in the system. By having a minimum quantity of 100 pounds of refrigerant, the International Mechanical Code recognizes that systems containing this amount or more present a significant risk in the event of a refrigerant leak or system maintenance.

Having stop valves allows maintenance personnel to safely isolate sections of the refrigerant piping, reducing the risk of exposure to high-pressure refrigerants and ensuring that refrigerant can be contained within specific areas for proper handling and service. In systems with less than 100 pounds of refrigerant, the risks are generally considered lower, and the added safety measures of stop valves may not be deemed necessary by the code.

This establishes a clear threshold where the potential hazards of refrigerant handling warrant additional precautionary measures, thereby promoting safety in mechanical systems.