Overpressure Protection, Relief Devices and Discharge

Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:

• CMC § 1308.8 High relevance — show source text

  1308.8 Pressure Limitation Requirements. Where piping systems serving appliances designed to operate with a gas supply pressure of 14 inches water column (3.5 kPa) or less are required to be equipped with overpressure protection by Section 1308.7, each overpressure protection device shall be adjusted to limit the gas pressure to each connected appliance to 2 psi (14 kPa) or less upon a failure of the line pressure regulator. [NFPA 54:5.8.2.1]

  1308.8.1 Overpressure Protection Required. Where piping systems serving appliances designed to operate with a gas supply pressure greater than 14 inches water column (3.5 kPa) are required to be equipped with overpressure protection by Section 1308.7, each overpressure protection device shall be adjusted to limit the gas pressure to each connected appliance as required by the appliance manufacturer’s installation instructions. [NFPA 54:5.8.2.2]

  1308.8.2 Overpressure Protection Devices. Each overpressure protection device installed to meet the requirements of this section shall be capable of limiting the pressure to its connected appliance(s) as required by this section independently of any other pressure control equipment in the piping system. [NFPA 54:5.8.2.3]

  1308.8.3 Detection of Failure. Each gas piping system for which an overpressure protection device is required by this section shall be designed and installed so that a failure of the primary pressure control device(s) is detectable. [NFPA 54:5.8.2.4]

  1308.8.4 Flow Capacity. If a pressure relief valve is used to meet the requirements of this section, it shall

  have a flow capacity such that the pressure in the protected system is maintained at or below the limits specified in Section 1308.8 under the following conditions:

  (1) The line pressure regulator for which the relief valve is providing overpressure protection has failed wide

  open.

  (2) The gas pressure at the inlet of the line pressure regulator for which the relief valve is providing overpressure protection is not less than the regulator’s normal operating inlet pressure. [NFPA 54:5.8.2.5]

  1308.9 Overpressure Protection Devices. Overpressure protection devices shall be one of the following:

  (1) Pressure relief valve.

  (2) Monitor regulator.

  (3) Series regulator installed upstream from the line regulator and set to continuously limit the pressure on the inlet of the line regulator to the maximum values specified by Section 1308.8 or less.

  (4) Automatic shutoff device installed in series with the line pressure regulator and set to shut off when the pressure on the downstream piping system reaches the maximum values specified by Section 1308.8 or less. This device shall be designed so that it will remain closed until manually reset. [NFPA 54:5.8.3.1]

  1308.9.1 Separate Devices. The devices in Section 1308.9 shall be installed either as an integral part of the service or line pressure regulator or as separate units. Where separate overpressure protection devices are installed, they shall comply with Section 1308.9.2 through Section 1308.9.7. [NFPA 54:5.8.3.2]

  1308.9.2 Construction and Installation. All overpressure protection devices shall meet the following requirements:

• CMC § 1308.8 High relevance — show source text

  have a flow capacity such that the pressure in the protected system is maintained at or below the limits specified in Section 1308.8 under the following conditions:

  (1) The line pressure regulator for which the relief valve is providing overpressure protection has failed wide

  open.

  (2) The gas pressure at the inlet of the line pressure regulator for which the relief valve is providing overpressure protection is not less than the regulator’s normal operating inlet pressure. [NFPA 54:5.8.2.5]

  1308.9 Overpressure Protection Devices. Overpressure protection devices shall be one of the following:

  (1) Pressure relief valve.

  (2) Monitor regulator.

  (3) Series regulator installed upstream from the line regulator and set to continuously limit the pressure on the inlet of the line regulator to the maximum values specified by Section 1308.8 or less.

  (4) Automatic shutoff device installed in series with the line pressure regulator and set to shut off when the pressure on the downstream piping system reaches the maximum values specified by Section 1308.8 or less. This device shall be designed so that it will remain closed until manually reset. [NFPA 54:5.8.3.1]

  1308.9.1 Separate Devices. The devices in Section 1308.9 shall be installed either as an integral part of the service or line pressure regulator or as separate units. Where separate overpressure protection devices are installed, they shall comply with Section 1308.9.2 through Section 1308.9.7. [NFPA 54:5.8.3.2]

  1308.9.2 Construction and Installation. All overpressure protection devices shall meet the following requirements:

  (1) Be constructed of materials so that the operation of the device is not impaired by corrosion of external parts by the atmosphere or of internal parts by the gas.

  (2) Be designed and installed so they can be operated to determine whether the valve is free. The devices shall also be designed and installed so they can be tested to determine the pressure at which they operate and be examined for leakage when in the closed position. [NFPA 54:5.8.4]

  1308.9.3 External Control Piping. External control piping shall be designed and installed so that damage to the control piping of one device does not render both the regulator and the overpressure protective device inoperative. [NFPA 54:5.8.5]

  1308.9.4 Setting. Each pressure limiting or pressure relieving device shall be set so that the gas pressure supplied to the connected appliance(s) does not exceed the limits specified in Section 1308.8 and Section 1308.8.1.

  [NFPA 54:5.8.6]

  1308.9.5 Unauthorized Operation. Where unauthorized operation of any shutoff valve could render a pres

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  FUEL GAS PIPING

  TABLE 1308.12

  MANUAL GAS VALVE STANDARDS

  [NFPA 54: TABLE 5.11]

• CMC § 1112.13 High relevance — show source text

  1112.13 Rating of Pressure-Relief Device. . . . . . . . . . . . . . . . . . . . . . 244

  1112.14 Rating of Rupture Members and Fusible Plugs . . . . . . . . . . . . . . . . 244

  1113.0 Overpressure Protection. . . . . . . . 244

  1113.1 General. . . . . . . . . . . . . . . . . . . . . 244

  1113.2 Type of Protection . . . . . . . . . . . . 245

  1113.3 Discharging into Lowside of System . . . . . . . . . . . . . . . . . . . . . 245

  1113.4 Parallel Pressure-Relief Devices . . 245

  1113.5 Discharge Capacity . . . . . . . . . . . 245

  1113.6 Three-Way Valve . . . . . . . . . . . . . 245

  1114.0 Special Discharge Requirements. . 245

  1114.1 General. . . . . . . . . . . . . . . . . . . . . 245

  1114.2 Design Requirements . . . . . . . . . . 245

  1114.3 Testing . . . . . . . . . . . . . . . . . . . . . 245

  1115.0 Labeling and Identification . . . . . . 245

  1115.1 General. . . . . . . . . . . . . . . . . . . . . 245

  1115.2 Volume and Type . . . . . . . . . . . . . 245

  1115.3 Permanent Sign . . . . . . . . . . . . . . 245

  1115.4 Marking of Pressure-Relief Devices. . . . . . . . . . . . . . . . . . . . . 245

  1115.5 Nameplate . . . . . . . . . . . . . . . . . . 245

  1116.0 Testing of Refrigeration Equipment . . . . . . . . . . . . . . . . . . 246

  1116.1 Factory Tests . . . . . . . . . . . . . . . . 246

  1116.2 Field Tests . . . . . . . . . . . . . . . . . . 246

  1116.3 Test Gases . . . . . . . . . . . . . . . . . . 246

  1116.4 Declaration . . . . . . . . . . . . . . . . . . 246

  1116.5 Brine Systems . . . . . . . . . . . . . . . 247

  1117.0 Refrigerant-Containing Pressure Vessels . . . . . . . . . . . . . . . . . . . . . 247

  1117.1 Inside Dimensions 6 Inches

  or Less . . . . . . . . . . . . . . . . . . . . . 247

  1117.2 Inside Dimensions More than

  6 Inches . . . . . . . . . . . . . . . . . . . . 247

  1117.3 Pressure Vessels for 15 psig or Less . . . . . . . . . . . . . . . . . . . . . 247

• CMC § 1112.1 High relevance — show source text

  1112.1 General. . . . . . . . . . . . . . . . . . . . . 241

  1112.2 Positive Displacement Compressor . . . . . . . . . . . . . . . . . 241

  1112.3 Liquid-Containing Portions of Systems . . . . . . . . . . . . . . . . . . 241

  1112.4 Evaporators . . . . . . . . . . . . . . . . . 241

  1112.5 Hydrostatic Expansion . . . . . . . . . 241

  1112.6 Actuation. . . . . . . . . . . . . . . . . . . . 242

  1112.7 Stop Valves Prohibited . . . . . . . . . 242

  1112.8 Location . . . . . . . . . . . . . . . . . . . . 242

  1112.9 Materials . . . . . . . . . . . . . . . . . . . . 242

  1112.10 Pressure-Relief Valve Setting . . . . 242

  1112.11 Discharge from Pressure-Relief Devices. . . . . . . . . . . . . . . . . . . . . 242

  1112.12 Discharge Piping . . . . . . . . . . . . . 243

  Table 1112.12.4 Atmospheric Pressure at Nominal

  Installation Elevation. . . . . . . . . . . 244

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  TABLE OF CONTENTS

  1112.13 Rating of Pressure-Relief Device. . . . . . . . . . . . . . . . . . . . . . 244

  1112.14 Rating of Rupture Members and Fusible Plugs . . . . . . . . . . . . . . . . 244

  1113.0 Overpressure Protection. . . . . . . . 244

  1113.1 General. . . . . . . . . . . . . . . . . . . . . 244

  1113.2 Type of Protection . . . . . . . . . . . . 245

  1113.3 Discharging into Lowside of System . . . . . . . . . . . . . . . . . . . . . 245

  1113.4 Parallel Pressure-Relief Devices . . 245

  1113.5 Discharge Capacity . . . . . . . . . . . 245

  1113.6 Three-Way Valve . . . . . . . . . . . . . 245

  1114.0 Special Discharge Requirements. . 245

  1114.1 General. . . . . . . . . . . . . . . . . . . . . 245

  1114.2 Design Requirements . . . . . . . . . . 245

  1114.3 Testing . . . . . . . . . . . . . . . . . . . . . 245

  1115.0 Labeling and Identification . . . . . . 245

  1115.1 General. . . . . . . . . . . . . . . . . . . . . 245

  1115.2 Volume and Type . . . . . . . . . . . . . 245

• CMC § 9.9.4 High relevance — show source text

  [ASHRAE 15:9.9.4]

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  REFRIGERATION

  1112.0 Pressure-Relief Devices.

  1112.1 General. Refrigeration systems shall be protected by a pressure-relief device or other approved means to safely relieve pressure due to fire or abnormal conditions. [ASHRAE 15:9.4.1] 1112.2 Positive Displacement Compressor. A positive displacement compressor with a stop valve in the discharge connection shall be equipped with a pressure-relief device that is sized, and with a pressure setting, in accordance with the compressor manufacturer to prevent rupture of the compressor or to prevent the pressure from increasing to more than 10 percent above the maximum allowable working pressure of any other component located in the discharge line between the compressor and the stop valve or in accordance with Section 1113.5, whichever is larger. The pressure-relief device shall discharge into the low-pressure side of the system or in accordance with Section 1112.11.

  Exception: Hermetic refrigerant motor-compressors that are listed and have a displacement not more than 50 cubic feet per minute (1.42 m [3] /min).

  The relief device(s) shall be sized based on compressor flow at the following conditions:

  (1) For compressors in single-stage systems and high-stage compressors of other systems, the flow shall be calculated based on 50°F (10°C) saturated suction temperature at the compressor suction.

  (2) For low-stage or booster compressors in compound refrigerating systems, the compressors that are capable of running only where discharging to the suction of a high-stage compressor, the flow shall be calculated based on the saturated suction temperature equal to the design operating intermediate temperature.

  (3) For low-stage compressors in cascade systems, the compressors that are located in the lower-temperature stage(s) of cascade systems, the flow shall be calculated based on the suction pressure being equal to the pressure setpoint of the pressure-relieving devices that protect the lowside of the stage against overpressure.

  Exceptions: For Section 1112.2(1), Section 1112.2(2), and Section 1112.2(3), the discharge capacity of the relief device shall be permitted to be the minimum regulated flow rate of the compressor where the following conditions are met:

  (1) The compressor is equipped with capacity regulation.

  (2) Capacity regulation actuates to a flow at not less than 90 percent of the pressure-relief device setting.

  (3) A pressure-limiting device is installed and set in accordance with the requirements of Section 1111.0.

  [ASHRAE 15:9.8] 1112.3 Liquid-Containing Portions of Systems. Liquid-containing portions of systems, including piping, that is isolated from pressure-relief devices required elsewhere, and that develops pressures exceeding their working design pressures due to temperature rise, shall be protected by the installation of pressure-relief devices. 1112.4 Evaporators. Heat exchanger coils located downstream, or upstream within 18 inches (457 mm), of a heating source and capable of being isolated shall be fitted with a

• CMC § 3.785 High relevance — show source text

  INSTALLED EQUIVALENT DIRECT RADIATION2 (square feet)	TANK CAPACITY (gallons)
  Up to 350	18
  Up to 450	21
  Up to 650	24
  Up to 900	30
  Up to 1100	35
  Up to 1400	40
  Up to 1600	2 to 30
  Up to 1800	2 to 30
  Up to 2000	2 to 35
  Up to 2400	2 to 40

  For SI units: 1 gallon = 3.785 L, 1 square foot = 0.0929 m [2]

  Notes: 1 Based on a two-pipe system with an average operating water temperature of 170°F (77°C), using cast-iron column radiation with a heat emission rate of 150 British thermal units per square foot hour [Btu/(ft [2] - h)] (473 W/m [2] ) equivalent direct radiation. 2 For systems that exceed 2400 square feet (222.9 m 2 ) of installed equivalent direct water radiation, the required capacity of the cushion tank shall be increased on the basis of 1 gallon (4 L) tank capacity per 33 square feet (3.1 m [2] ) of additional equivalent direct radiation.

  TABLE 1004.4(2) EXPANSION TANK CAPACITIES FOR FORCED HOT WATER SYSTEMS [1]

  SYSTEM VOLUME2 (gallons)	TANK CAPACITY DIAPHRAGM TYPE (gallons)	TANK CAPACITY NON- DIAPHRAGM TYPE (gallons)
  100	9	15
  200	17	30
  300	25	45
  400	33	60
  500	42	75
  1000	83	150
  2000	165	300

  For SI units: 1 gallon = 3.785 L

  Notes: 1 Based on an average operating water temperature of 195°F (91°C), a fill pressure of 12 psig (83 kPa), and an operating pressure of not more than 30 psig (207 kPa). 2 Includes volume of water in boiler, radiation, and piping, not including expansion tank.

  1005.0 Safety or Relief Valve Discharge.

  1005.1 General. Pressurized vessels or boilers shall be provided with overpressure protection by means of a listed pressure relief valve installed in accordance with the manufacturer’s

  installation instructions.

  1005.2 Discharge Piping. The discharge piping serving a temperature relief valve, pressure relief valve, or combination of both shall have no valves, obstructions, or means of isolation and provided with the following:

  (1) Not less than the size of the valve outlet and shall discharge full size to the flood level of the area receiving the discharge and pointing down.

  (2) Materials shall be rated at not less than the operating temperature of the system and approved for such use or shall comply with ASME A112.4.1.

• CMC § 1112.14 High relevance — show source text

  Where:

  C = Rated discharge capacity expressed as mass flow of air, pounds per minute.

  d = Smallest of the internal diameter of the inlet pipe, retaining flanges, fusible plug, and rupture member , inches.

  For rupture members:

  [Equation 1112.14(3)]

  P1 = (rated pressure in psig x 1.1) + 14.7 psia

  For fusible plugs:

  P1 = Absolute saturation pressure corresponding to the stamped temperature melting point of the fusible plug or the critical pressure of the refrigerant used, whichever is smaller, pound-force per square inch atmosphere, psia. [ASHRAE 15:9.7.7]

  For SI units:1 pound per minute = 0.00756 kg/s

  1113.0 Overpressure Protection.

  1113.1 General. Pressure vessels shall be provided with overpressure protection in accordance with ASME BPVC Section VIII.1. Pressure vessels containing liquid refrigerant that are capable of being isolated by stop valves from other parts of a refrigerating system shall be provided with overpressure protection. Pressure relief devices or fusible plugs shall be sized in accordance with Section 1113.5. [ASHRAE 15:9.7.1, 9.7.2]

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  Unless the maximum allowable back pressure ( P0 ) is specified by the relief valve manufacturer, the following maximum allowable back pressure values shall be used for P0, where P is the set pressure and Pa is atmospheric pressure at the nominal elevation of the installation (see Table 1112.12.4):

  (1) For conventional relief valves: 15 percent of set

  pressure:

  P0 = (0.15• P )+ Pa [Equation 1112.12.4(2)] (2) For balanced relief valves: 25 percent of set pres sure:

  P0 = (0.25• P )+ Pa [Equation 1112.12.4(3)]

  (3) For rupture disks alone, fusible plugs, or pilot-operated relief devices: 50 percent of set pressure:

  P0 = (0.50• P )+ Pa [Equation 1112.12.4(4)]

  For fusible plugs, P shall be the saturated absolute pressure for the stamped temperature melting point of the fusible plug or the critical pressure of the refrigerant used, whichever is smaller. [ASHRAE 15:9.7.9.3.1, 9.7.9.3.2]

  TABLE 1112.12.4

  ATMOSPHERIC PRESSURE AT NOMINAL INSTALLATION ELEVATION ( Pa )

  [ASHRAE 15: TABLE 9-2]

• CMC § 304.8 High relevance — show source text

  For SI units: 1 foot = 304.8 mm, 1 pound-force per square inch = 6.8947 kPa

  1112.12.5 Simultaneous Operation. When outlets of two or more relief devices or fusible plugs, which are

  TABLE 1112.12.4

  ATMOSPHERIC PRESSURE AT NOMINAL INSTALLATION ELEVATION ( Pa )

  [ASHRAE 15: TABLE 9-2]

  For SI units: 1 foot = 304.8 mm, 1 pound-force per square inch = 6.8947 kPa

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  REFRIGERATION

  1113.2 Type of Protection. Pressure vessels with an internal gross volume of 3 cubic feet (0.1 m [3] ) or less shall use one or more pressure relief devices or a fusible plug. Pressure vessels of more than 3 cubic feet (0.1 m [3] ) but less than 10 cubic feet (0.28 m [3] ) internal gross volume shall use one or more pressure relief devices. Fusible plugs shall not be used.

  [ASHRAE 15:9.7.2.1, 9.7.2.2]

  1113.3 Discharging into Lowside of System. For pressure-relief valves discharging into the lowside of the system, a single relief valve (not rupture member) of the required relieving capacity shall not be used on vessels of 10 cubic feet (0.28 m [3] ) or more internal gross volume except under the conditions permitted in Section 1112.11.3. [ASHRAE 15:9.7.3]

  1113.4 Parallel Pressure-Relief Devices. Two or more

  pressure-relief devices in parallel to obtain the required capacity shall be considered as one pressure-relief device. The discharge capacity shall be the sum of the capacities required for each pressure vessel being protected.

  1113.5 Discharge Capacity. The minimum required discharge capacity of the pressure-relief device or fusible plug for a pressure vessel shall be determined in accordance with ASHRAE 15.

  1113.6 Three-Way Valve. Pressure vessels of 10 cubic feet (0.28 m [3] ) or more internal gross volume shall use one or more rupture member(s) or dual pressure-relief valves where discharging to the atmosphere. Dual pressure-relief valves shall be installed with a three-way valve to allow testing or repair. Where dual relief valves are used, the valve shall comply with Section 1113.5.

  Exception: A single relief valve shall be permitted on pressure vessels of 10 cubic feet (0.28 m [3] ) or more internal gross volume where in accordance with the following conditions:

  (1) The relief valves are located on the lowside of the sys tem.

  (2) The vessel is provided with shutoff valves designed to allow pumpdown of the refrigerant charge of the pressure vessel.

  (3) Other pressure vessels in the system are separately protected in accordance with Section 1113.1. [ASHRAE 15:9.7.2.3]

  1114.0 Special Discharge Requirements.

• CMC § 1208.10.1 Medium relevance — show source text

  1208.10.1 Overpressure Protection Required. Where piping systems serving appliances designed to operate with a gas supply pressure greater than 14 inches water column (3.5 kPa) are required to be equipped with overpressure protection by Section 1208.8, each overpressure protection device shall be adjusted to limit the gas pressure to each connected appliance as required by the appliance manufacturer’s installation instructions. [NFPA 54:5.8.2.2]

  1208.10.2 Overpressure Protection Devices. Each overpressure protection device installed to meet the requirements of this section shall be capable of limiting the pressure to its connected appliance(s) as required by this section independently of any other pressure control equipment in the piping system. [NFPA 54:5.8.2.3] 1208.10.3 Detection of Failure. Each gas piping system for which an overpressure protection device is required by this section shall be designed and installed so that a failure of the primary pressure control device(s) is detectable. [NFPA 54:5.8.2.4] 1208.10.4 Flow Capacity. If a pressure relief valve is used to meet the requirements of this section, it shall have a flow capacity such that the pressure in the protected system is maintained at or below the limits specified in Section 1208.10 under the following conditions:

  (1) The line pressure regulator for which the relief valve is providing overpressure protection has failed wide

  open.

  (2) The gas pressure at the inlet of the line pressure regulator for which the relief valve is providing overpressure protection is not less than the regulator’s normal operating inlet pressure. [NFPA 54:5.8.2.5]

  1208.11 Backpressure Protection. Protective devices shall be installed as close to the equipment as practical where the design of equipment connected is such that air, oxygen, or standby gases could be forced into the gas supply system.

  Gas and air combustion mixers incorporating double diaphragm “zero” or “atmosphere” governors or regulators shall require no further protection unless connected directly to compressed air or oxygen at pressures of 5 psi (34 kPa) or more. [NFPA 54:5.9.1.1 – 5.9.1.2]

  1208.11.1 Protective Devices. Protective devices

  shall include but not be limited to the following:

  (1) Check valves.

  (2) Three-way valves (of the type that completely closes one side before starting to open the other side).

  (3) Reverse flow indicators controlling positive shutoff valves.

  (4) Normally closed air-actuated positive shutoff pressure regulators. [NFPA 54:5.9.2]

  1208.12 Low-Pressure Protection. A protective device shall be installed between the meter and the appliance or equipment if the operation of the appliance or equipment is such that it could produce a vacuum or a dangerous reduction in gas pressure at the meter. Such protective devices include, but are not limited to, mechanical, diaphragm-operated, or electrically operated low-pressure shutoff valves. [NFPA 54:5.10]

  1208.13 Shutoff Valves. Shutoff valves shall be selected in

  accordance with Table 1208.13. Shutoff valves of size 1 inch

  (25 mm) National Pipe Thread and smaller shall be listed and labeled. Where used outdoors, such use shall be in accordance with the manufacturer’s recommendation. [NFPA 54:5.11]

• CMC § 9.5.2 Medium relevance — show source text

  relief-valve inlet. [ASHRAE 15:9.5.2]

  1112.11 Discharge from Pressure-Relief Devices. Pressure-relief systems designed for vapor shall comply with Section 1112.11.1 through Section 1112.11.4.1.

  1112.11.1 Discharging Location Interior to Build- ing. Pressure-relief devices, including fusible plugs, serving refrigeration systems shall be permitted to discharge to the interior of a building where in accordance with all of the following:

  (1) The system contains less than 110 pounds (49.9 kg) of a Group A1 or A2L refrigerant.

  (2) The system contains less than 6.6 pounds (2.99 kg) of a Group A2, B1, B2 or B2L refrigerant.

  (3) The system does not contain any quantity of a Group A3 or B3 refrigerant.

  (4) The system is to be installed in a machinery room in accordance with Section 1106.0.

  (5) The refrigerant concentration limits in Section 1104.2 are not exceeded. Refrigeration systems that do not comply with the above requirements shall comply with the requirements of Section 1112.11.2 through Section 1112.11.4. [ASHRAE 15:9.7.8.1]

  1112.11.2 Discharging Location Exterior to Build- ing. Pressure-relief devices designed to discharge external to the refrigeration system shall be arranged to discharge outside of a building and shall be in accordance with the following:

  (1) The point of vent discharge shall be located not less than 15 feet (4572 mm) above the adjoining ground level.

  Exception: Outdoor systems containing Group A1 refrigerant shall be permitted to discharge at any elevation where the point of discharge is located in an access-controlled area accessible to authorized personnel only.

  (2) The point of vent discharge shall be located not less than 20 feet (6096 mm) from windows, building ventilation openings, pedestrian walkways, or building exits.

  (3) For heavier-than-air refrigerants, the point of vent discharge shall be located not less than 20 feet (6096 mm) horizontally from below-grade walkways, entrances, pits, or ramps where a release of the entire system charge into such a space would yield a concentration of refrigerant in excess of the RCL. The direct discharge of a relief vent into enclosed outdoor spaces, such as a courtyard with walls on all sides, shall not be permitted where a release of the entire system charge into such a space would yield a concentration of refrigerant in excess of the RCL. The volume for the refrigerant concentration calculation shall be determined using the gross area of the space and a height of 8.2 feet (2499 mm), regardless of the actual height of the enclosed space.

  (4) The termination point of a vent discharge line shall be made in a manner that prevents discharged refrigerant from spraying directly onto personnel that are capable of being in the vicinity.

  (5) The termination point of vent discharge lines shall be made in a manner that prevents foreign material or debris from entering the discharge piping.

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  REFRIGERATION

• CMC § 1306.1 Medium relevance — show source text

  1306.1 Disconnection . . . . . . . . . . . . . . . . 276

  1306.2 Notice . . . . . . . . . . . . . . . . . . . . . . 276

  1306.3 Capped Outlets. . . . . . . . . . . . . . . 276

  1307.0 Temporary Use of Gas . . . . . . . . . 276

  1307.1 General. . . . . . . . . . . . . . . . . . . . . 276

  1308.0 Gas Piping System Design, Materials, and Components . . . . . 276

  1308.1 Installation of Piping System . . . . 276

  1308.2 Interconnections Supplying Separate Users. . . . . . . . . . . . . . . 276

  1308.3 Sizing of Gas Piping Systems . . . 277

  1308.4 Acceptable Piping Materials and Joining Methods . . . . . . . . . . 277

  Table 1308.3.1 Approximate Gas Input for Typical Appliances . . . . . . . . . . . . 277

  Table 1308.4.6.2 Specifications for Threading Metallic Pipe . . . . . . . . . . . . . . . . . 278

  1308.5 Gas Meters . . . . . . . . . . . . . . . . . . 280

  1308.6 Gas Pressure Regulators . . . . . . . 280

  1308.7 Overpressure Protection. . . . . . . . 281

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  TABLE OF CONTENTS

  1308.8 Pressure Limitation

  Requirements . . . . . . . . . . . . . . . . 281

  1308.9 Overpressure Protection Devices. . . . . . . . . . . . . . . . . . . . . 281

  1308.10 Backpressure Protection . . . . . . . 282

  1308.11 Low-Pressure Protection . . . . . . . 282

  1308.12 Shutoff Valves . . . . . . . . . . . . . . . 282

  Table 1308.12 Manual Gas Valve Standards. . . . 282

  1308.13 Expansion and Flexibility . . . . . . . 282

  1308.14 Pressure Regulator and Pressure Control Venting . . . . . . . 282

  1309.0 Excess Flow Valve . . . . . . . . . . . . 283

  1309.1 General. . . . . . . . . . . . . . . . . . . . . 283

  1310.0 Gas Piping Installation . . . . . . . . . 283

  1310.1 Piping Underground . . . . . . . . . . . 283

  1310.2 CSST Piping Systems . . . . . . . . . 284

  1310.3 Installation of Aboveground Piping . . . . . . . . . . . . . . . . . . . . . . 284

  Table 1310.3.5.1 Support of Piping . . . . . . . . . . . . . 285

• CMC § 1112.12.4. Medium relevance — show source text

  ( P [2] 0 P 22 ) d - ln ( P0P2 )

  f - C [2] r 6 - f

  2025 CALIFORNIA MECHANICAL CODE 243

  ), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

  REFRIGERATION

  expected to operate simultaneously, connect to a common discharge pipe, the common pipe shall be sized large enough to prevent the back pressure at each pressure-relief device from exceeding the maximum allowable back pressure in accordance with Section 1112.12.4.

  [ASHRAE 15:9.7.9.3.3]

  1112.13 Rating of Pressure-Relief Device. The rated discharge capacity of a pressure-relief device expressed in pounds of air per minute (kg/s), shall be determined in accordance with ASME BPVC Section VIII.1. Pipe and fittings between the pressure-relief valve and the parts of the system it protects shall have not less than the area of the pressurerelief valve inlet area. [ASHRAE 15:9.7.6]

  1112.14 Rating of Rupture Members and Fusible Plugs. The rated discharge capacity of a rupture member or fusible plug discharging to the atmosphere under critical flow conditions, in pounds of air per minute (kg/s), shall be determined in accordance with the following formulas:

  C = 0.64 P l d [2] [Equation 1112.14(1)]

  d = 1.25 √ C / P l [Equation 1112.14(2)]

  Where:

  C = Rated discharge capacity expressed as mass flow of air, pounds per minute.

  d = Smallest of the internal diameter of the inlet pipe, retaining flanges, fusible plug, and rupture member , inches.

  For rupture members:

  [Equation 1112.14(3)]

  P1 = (rated pressure in psig x 1.1) + 14.7 psia

  For fusible plugs:

  P1 = Absolute saturation pressure corresponding to the stamped temperature melting point of the fusible plug or the critical pressure of the refrigerant used, whichever is smaller, pound-force per square inch atmosphere, psia. [ASHRAE 15:9.7.7]

  For SI units:1 pound per minute = 0.00756 kg/s

  1113.0 Overpressure Protection.

  1113.1 General. Pressure vessels shall be provided with overpressure protection in accordance with ASME BPVC Section VIII.1. Pressure vessels containing liquid refrigerant that are capable of being isolated by stop valves from other parts of a refrigerating system shall be provided with overpressure protection. Pressure relief devices or fusible plugs shall be sized in accordance with Section 1113.5. [ASHRAE 15:9.7.1, 9.7.2]

  »

  Unless the maximum allowable back pressure ( P0 ) is specified by the relief valve manufacturer, the following maximum allowable back pressure values shall be used for P0, where P is the set pressure and Pa is atmospheric pressure at the nominal elevation of the installation (see Table 1112.12.4):