Relief valves are commonplace in hvacr systems, but choosing the right one to install is not a simple task. A number of factors must be considered when selecting and installing relief valves. For example:
• Provide a pressure vessel that will permit the relief valve to be set at least 25 percent above the maximum system pressure. However, the relief valve setting cannot exceed the maximum allowable working pressure as stamped on the vessel the relief valve is protecting.
• Select a relief valve to have sufficient capacity.
• Select a relief valve suitable for the refrigerant.
• Install the relief valve so that it will be exposed to refrigerant vapor.
• Install the relief valves where they are accessible for inspection and replacement.
• Do not discharge relief valves prior to installation or when pressure testing the system.
• Use the proper size and length of discharge tube or pipe. Correct sizing is required to prevent back pressure from building up in the discharge line, preventing the relief valve from discharging at its rated capacity.
• The use of a three-way valve with two relief devices, which complies with two relief devices, which complies with the code requirement for vessels 10 cubic feet or more in gross volume, is recommended for a any installation containing a large quantity of expensive refrigerant.
• When the outlets of two or more relief devices are connected to a common header, the size of the header must be large enough to remain unaffected by back pressure even if all the relief devices were to discharge simultaneously.
By following these simple rules and recommendations, you can ensure that a system is protected by a properly functioning relief valve.
Source: Henry Technologies
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