G3 Tools and Testing Instruments 2 — Questions and Answers
Question 1: What instrument measures gas pressure at an appliance gas valve?
- Thermometer
- Manometer or digital pressure gauge (Correct answer)
- Ammeter
- Tachometer
Correct answer: Manometer or digital pressure gauge
A manometer measures gas pressure in inches of water column.
Standard residential gas pressure is approximately 7 inches WC at the meter and 3.5 inches WC manifold pressure.
Question 2: What does a combustion analyzer measure?
- Gas pipe diameter
- Flue gas components including CO, CO2, O2, and temperature (Correct answer)
- Gas flow rate
- Electrical voltage at gas valve
Correct answer: Flue gas components including CO, CO2, O2, and temperature
It measures flue gas components to evaluate combustion efficiency and safety.
High CO readings indicate incomplete combustion requiring attention.
Question 3: What is a combustible gas detector used for?
- Measuring BTU content
- Detecting the presence and location of gas leaks (Correct answer)
- Controlling gas pressure
- Measuring pipe temperature
Correct answer: Detecting the presence and location of gas leaks
It senses combustible gases in air to help locate leaks.
Moved slowly along connections, its sensitivity can detect leaks that soap solution might miss.
Question 4: When should a CO detector be used during service work?
- Only when homeowner requests
- Every time a gas appliance is serviced as standard practice (Correct answer)
- Only for commercial
- Only during new installations
Correct answer: Every time a gas appliance is serviced as standard practice
A personal CO detector should be used during every gas service call.
Technicians should use both a personal CO monitor and combustion analyzer CO readings.
Question 5: What is a pipe wrench used for in gas installation?
- Cutting pipe to length
- Gripping and turning threaded pipe and fittings (Correct answer)
- Measuring pipe diameter
- Deburring cut ends
Correct answer: Gripping and turning threaded pipe and fittings
Serrated jaws grip round pipe for tightening and loosening threaded connections.
Two wrenches are used together to prevent stress on existing connections.
Question 6: What is a draft gauge used for?
- Measuring gas pressure at burner
- Measuring draft (pressure difference) in the vent system (Correct answer)
- Checking gas valve electrical signal
- Testing vent pipe material strength
Correct answer: Measuring draft (pressure difference) in the vent system
A draft gauge measures the negative pressure that draws combustion products through the vent.
Typical readings are -0.02 to -0.05 inches WC in the vent connector.
G3 Tools and Testing Instruments 2
What instrument measures gas pressure at an appliance gas valve?