G3 G3 - Gas Technician Level 3 Pressure Regulation and Control Questions and Answers 2 — Questions and Answers
Question 1: An overpressure protection device (OPD) on a gas regulator is designed to:
- Boost pressure during peak demand
- Shut off or limit gas flow if downstream pressure exceeds a safe level (Correct answer)
- Filter gas before it reaches the regulator
- Measure gas usage automatically
Correct answer: Shut off or limit gas flow if downstream pressure exceeds a safe level
OPDs protect downstream piping and appliances by closing or relieving gas flow when outlet pressure rises above a set threshold.
Question 2: When checking gas pressure with a manometer, the technician connects the instrument to:
- The gas meter glass directly
- A pressure test port or tap on the appliance manifold or supply piping (Correct answer)
- The flue outlet
- The electrical panel
Correct answer: A pressure test port or tap on the appliance manifold or supply piping
Gas pressure is measured at dedicated test ports on the supply manifold or piping, ensuring an accurate and safe reading.
Question 3: For LP (propane) gas appliances in the US, the typical operating manifold pressure is:
- 3.5 in. W.C.
- 11 in. W.C. (Correct answer)
- 7 in. W.C.
- 2 psi
Correct answer: 11 in. W.C.
LP (propane) appliances in the US are designed to operate at 11 in. W.C. manifold pressure, compared to 3.5 in. W.C. for natural gas.
Question 4: A two-stage LP regulator system uses a first-stage regulator to reduce tank pressure to approximately:
- 11 in. W.C.
- 10 psi (Correct answer)
- 2 psi
- 60 psi
Correct answer: 10 psi
In a two-stage LP system, the first-stage regulator reduces high tank pressure (up to 200 psi) to approximately 10 psi intermediate pressure.
Question 5: If a gas appliance has a weak or lazy flame and the manifold pressure is found to be lower than specified, the technician should check:
- The flue pipe diameter
- The supply pressure at the regulator outlet and the regulator set-point adjustment (Correct answer)
- The pilot orifice size only
- The heat exchanger for cracks
Correct answer: The supply pressure at the regulator outlet and the regulator set-point adjustment
Low manifold pressure typically traces back to an incorrectly set or failing regulator, low line pressure, or a partially closed supply valve.
Question 6: A regulator that allows full supply pressure to pass to downstream piping without reduction is said to have experienced:
- Droop
- Lockup
- Regulator failure (wide open) (Correct answer)
- Surge flow
Correct answer: Regulator failure (wide open)
A failed-open regulator passes full upstream pressure downstream, creating a serious overpressure hazard for piping and appliances.
G3 G3 - Gas Technician Level 3 Pressure Regulation and Control Questions and Answers 2
An overpressure protection device (OPD) on a gas regulator is designed to: