1310.14 Systems Containing Flammable Gas-Air

Mixtures. Systems containing flammable gas-air mixtures shall be in accordance with Section 1310.14.1 through Section 1310.14.6.

1310.14.1 Required Components. A central premix system with a flammable mixture in the blower or compressor shall consist of the following components: (1) Gas-mixing machine in the form of an automatic

gas-air proportioning device combined with a downstream blower or compressor. (2) Flammable mixture piping, minimum Schedule 40. (3) Automatic firecheck(s). (4) Safety blowout(s) or backfire preventers for systems

utilizing flammable mixture lines above 2 ¹ ⁄ 2 inches (64 mm) nominal pipe size or the equivalent. [NFPA 54:7.11.1] 1310.14.2 Optional Components. The following components shall also be permitted to be utilized in any type of central premix system: (1) Flowmeter(s) (2) Flame arrester(s) [NFPA 54:7.11.2] 1310.14.3 Additional Requirements. Gas-mixing machines shall have nonsparking blowers and shall be constructed so that a flashback does not rupture machine casings. [NFPA 54:7.11.3]

1310.14.4 Special Requirements for Mixing Blowers. A mixing blower system shall be limited to applications with minimum practical lengths of mixture piping, limited to a maximum mixture pressure of 10 inches water column (2.5 kPa) and limited to gases containing no more than 10 percent hydrogen. The blower

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(3) Outlets shall be located far enough from floors, walls,

patios, slabs, and ceilings to permit the use of wrenches without straining, bending, or damaging the piping. (4) The unthreaded portion of gas piping outlets shall extend

not less than 1 inch (25.4 mm) through finished ceilings or indoor or outdoor walls. (5) The unthreaded portion of gas piping outlets shall extend

not less than 2 inches (51 mm) above the surface of floors or outdoor patios or slabs. (6) The provisions of Section 1310.10(4) and Section

1310.10(5) shall not apply to listed quick-disconnect devices of the flush-mounted type or listed gas convenience outlets. Such devices shall be installed in accordance with the manufacturer’s installation instructions.

[NFPA 54:7.7.1.1 – 7.7.1.6] 1310.10.1 Cap Outlets. Each outlet, including a valve, shall be closed gastight with a threaded plug or cap immediately after installation and shall be left closed until the appliance or equipment is connected thereto. When an appliance or equipment is disconnected from an outlet and the outlet is not to be used again immediately, it shall be capped or plugged gastight. Exceptions: (1) Laboratory appliances installed in accordance with

Section 1312.3.1 shall be permitted. (2) The use of a listed quick-disconnect device with

integral shutoff or listed gas convenience outlet shall be permitted. [NFPA 54:7.7.2.1] 1310.10.1.1 Appliance Shutoff Valves. Appliance shutoff valves installed in fireplaces shall be removed and the piping capped gastight where the fireplace is used for solid fuel burning. [NFPA 54:7.7.2.2]