Fuel Gas Piping and Gas Appliances
What this domain tests
Gas piping materials and sizing, appliance connections, combustion air and venting, and safe testing of fuel gas systems.
Core rules
- The state adopts a fuel gas code from the NFPA 54 / IFGC family, and LP-gas work also involves New Hampshire LP-gas licensing requirements. Confirm the edition in force in the Board's rules rather than assuming one.
- Sizing uses the longest-length method: total the connected Btu/hr of all appliances, divide by heating value (about 1,000 Btu per cubic foot for natural gas, roughly 2,500 for propane vapor) to get cubic feet per hour, then read the table for the longest run and allowable drop (commonly ½ inch water column for low-pressure systems).
- Black steel, corrugated stainless steel tubing, and approved copper are typical; CSST must be bonded, piping supported and protected where it passes through masonry, and concealed unions are not allowed except at approved locations.
- Each appliance gets a listed shutoff valve, a union or connector, and a sediment trap ahead of the controls.
- Venting follows the appliance category: draft hood or fan-assisted, connector sloped up, no sagging, correct termination, combustion air from two openings or direct vent.
- Test with air or inert gas at the pressure and duration the adopted code requires, never with gas in the line; leak detection is soap solution, never a flame.
Worked example
Connected load: range 65,000 Btu/hr + water heater 40,000 + furnace 100,000 = 205,000 Btu/hr. Natural gas demand = 205,000 ÷ 1,000 = 205 cubic feet per hour. With a 60-foot longest run at ½-inch water column, the pipe table selects a size based on that 205 cfh figure - not on any single appliance.
Traps that cost marks
Sizing on the farthest appliance instead of total load; forgetting the sediment trap; assuming propane uses the same cubic-feet figure as natural gas; pressure-testing with the meter connected.