Journeyman Plumbers Exam Gas Piping and Appliances 3 — Questions and Answers
Question 1: A listed gas range requires a flexible connector. What is the maximum length allowed for a residential gas appliance connector?
- 2 feet
- 3 feet
- 4 feet
- 6 feet (Correct answer)
Correct answer: 6 feet
ANSI Z21.24 and NFPA 54 allow gas appliance connectors up to 6 feet in length for residential ranges, dryers, and similar appliances.
Question 2: Which venting category applies to a high-efficiency gas furnace with a flue gas temperature below 140°F and a positive vent pressure?
- Category I
- Category II
- Category III
- Category IV (Correct answer)
Correct answer: Category IV
Category IV appliances have positive vent pressure and low flue temperatures with condensing potential, requiring special sealed plastic vent pipe (PVC or CPVC).
Question 3: Gas piping must be electrically bonded. The bond connection should be made:
- At the gas meter only
- At every appliance connection
- To the gas piping system using a clamp upstream of any unions or isolating fittings (Correct answer)
- Between appliances only
Correct answer: To the gas piping system using a clamp upstream of any unions or isolating fittings
Bonding connects the metal gas piping to the electrical grounding system to prevent stray current and static buildup, and must be upstream of any isolating or dielectric fittings.
Question 4: What is the minimum BTU/hr input for a gas-fired water heater to require a dedicated combustion air opening?
- The requirement is based on the room volume, not the BTU rating alone (Correct answer)
- 50,000 BTU/hr
- 75,000 BTU/hr
- 100,000 BTU/hr
Correct answer: The requirement is based on the room volume, not the BTU rating alone
Combustion air requirements are determined by the total BTU input of all appliances in the space relative to the available room volume, not a single BTU threshold.
Question 5: CSST (corrugated stainless steel tubing) installed in a structure must be bonded because:
- It is not strong enough without bonding
- It is susceptible to lightning-induced surge damage that can cause pinhole leaks (Correct answer)
- It requires grounding to maintain gas pressure
- Building codes require bonding of all metallic pipe regardless of material
Correct answer: It is susceptible to lightning-induced surge damage that can cause pinhole leaks
Lightning-induced electrical surges can arc through CSST walls creating pinhole leaks; bonding dissipates the surge current safely.
Question 6: A gas appliance conversion from natural gas to LP (propane) typically requires:
- Only a pressure regulator change
- Only an orifice change
- Orifice replacement and regulator adjustment or replacement (Correct answer)
- No modifications — the appliances are interchangeable
Correct answer: Orifice replacement and regulator adjustment or replacement
LP gas has higher BTU content and different pressure than natural gas, so both the orifices (for proper flow) and the regulator (for correct pressure) must be changed.
Question 7: When testing a new gas piping system for leaks, which test medium is preferred and what pressure is typically used?
- Natural gas at normal operating pressure
- Air or nitrogen at 1.5 times the operating pressure or 3 psig minimum (Correct answer)
- Water at 100 psig
- Oxygen at 50 psig
Correct answer: Air or nitrogen at 1.5 times the operating pressure or 3 psig minimum
NFPA 54 requires a pressure test using air or inert gas (not the gas being served) at 1.5 times operating pressure or a minimum of 3 psig for medium/high pressure systems.
