G3 - Gas Technician Level 3 Tools and Testing Instruments Questions and Answers 1 — Questions and Answers
Question 1: When using a digital manometer to measure the manifold pressure of a natural gas appliance, what is the typical pressure reading a technician should expect to see?
- 10 to 13 inches of water column
- 28 to 30 PSI
- 3.5 to 7 inches of water column (Correct answer)
- 0.5 to 1 PSI
Correct answer: 3.5 to 7 inches of water column
The typical manifold pressure for a natural gas appliance is approximately 3.5 inches of water column, though the acceptable range can extend up to 7 inches W.C. Propane operates at a higher pressure, typically around 10-11 inches W.C. PSI is a much higher pressure unit not used for measuring standard manifold pressure.
Question 2: A technician is troubleshooting a gas valve that is failing to open. Using a multimeter, what is the first electrical test that should be performed on the valve's terminals after a call for heat is initiated?
- Resistance (Ohms) across the main coil
- Voltage (AC) to the valve operator (Correct answer)
- Continuity across the valve body
- Amperage draw of the solenoid
Correct answer: Voltage (AC) to the valve operator
The first step is to verify that the gas valve is receiving the correct voltage (typically 24 VAC) from the control board when there is a call for heat. If voltage is present but the valve doesn't open, then the technician can proceed to check the valve's internal resistance. Checking for voltage confirms if the problem is with the valve itself or the control circuit supplying it.
Question 3: Which of the following measurements is a primary function of a combustion analyzer?
- Measuring the specific gravity of the fuel gas
- Detecting the presence of unburned hydrocarbons in the room
- Calculating the dew point of the flue gases
- Measuring the concentration of Carbon Monoxide (CO) in the flue gas (Correct answer)
Correct answer: Measuring the concentration of Carbon Monoxide (CO) in the flue gas
A combustion analyzer is a crucial tool for ensuring safe and efficient appliance operation. Its primary function is to sample flue gases and measure key components like Carbon Monoxide (CO), Oxygen (O2), and flue gas temperature. This data helps a technician assess the combustion process and make necessary adjustments.
Question 4: When using an electronic combustible gas detector (sniffer) to locate a small leak on a gas pipe fitting, where should the technician place the sensor tip for the most accurate reading?
- Directly on top of the fitting
- At the lowest point below the fitting
- Slightly above and around the fitting for natural gas (Correct answer)
- At least 12 inches away from the fitting to avoid oversaturation
Correct answer: Slightly above and around the fitting for natural gas
Natural gas (methane) is lighter than air. Therefore, when a leak occurs, the gas will tend to rise. Placing the sensor tip slightly above and around the fitting allows the rising gas to be detected effectively. For propane, which is heavier than air, the sensor should be placed below the fitting.
Question 5: A technician needs to confirm that a safety shut-off solenoid coil within a gas valve is electrically sound and not broken internally. Which multimeter measurement should be used for this test with the power disconnected?
- AC Voltage
- Capacitance
- Resistance (Ohms) (Correct answer)
- DC Amperage
Correct answer: Resistance (Ohms)
With the power disconnected from the appliance, a resistance (Ohms) test can be performed on the solenoid coil. A definitive Ohm reading within the manufacturer's specified range indicates the coil winding is intact. An 'open' or infinite reading (OL) signifies a broken coil, and a reading of zero indicates a short circuit.
Question 6: Before using a portable electronic gas detector at the start of a workday, what is the essential safety check that must be performed to ensure the sensors and alarms are functioning correctly?
- A full 180-day calibration
- A battery charge test
- A bump test (Correct answer)
- A pressure test
Correct answer: A bump test
A bump test is a brief exposure of the detector to a known concentration of the target gas to verify that the sensors respond and the alarms (audible, visual, and vibratory) function correctly. This is a critical daily check to ensure the life-saving device can be trusted before entering a potentially hazardous area. Calibration is a more thorough adjustment done at longer intervals.
G3 - Gas Technician Level 3 Tools and Testing Instruments Questions and Answers 1
When using a digital manometer to measure the manifold pressure of a natural gas appliance, what is the typical pressure reading a technician should expect to see?