G3 - Gas Technician Level 3 Combustion and Venting Principles Questions and Answers

Question 1

A technician is servicing a natural draft gas furnace and observes soot buildup and discoloration around the burner area, indicating flame rollout.
Which of the following is the MOST likely cause of this issue?

Accepted Answer

A cracked heat exchanger

Answer

Excessively high gas pressure

Answer

A malfunctioning thermostat

Answer

Low voltage to the gas valve

Question 2

What is the primary function of a vent spillage switch on a Category I, natural draft appliance?

Accepted Answer

To shut down the appliance if it detects that flue gases are escaping from the draft hood.

Answer

To verify the inducer motor is running before ignition.

Answer

To increase the draft in the chimney during cold startups.

Answer

To monitor the temperature of the flame and ensure complete combustion.

Question 3

According to the CSA B149.1 code, what is the minimum required slope for a horizontal single-wall vent connector?

Accepted Answer

1/4 inch per foot upward towards the vent

Answer

1/8 inch per foot upward towards the vent

Answer

1/2 inch per foot upward towards the vent

Answer

1/4 inch per foot downward towards the appliance

Question 4

A technician is installing a gas water heater in a small, tightly sealed mechanical room. They are concerned about a 'negative pressure' condition developing. Which of the following scenarios would MOST likely create this condition?

Accepted Answer

Operating a large kitchen range hood exhaust fan in the adjacent area.

Answer

The water heater and furnace sharing a common vent.

Answer

Installing the water heater on an outside wall.

Answer

Using a B-vent for the exhaust.

Question 5

Which of the following is a primary requirement for ensuring complete combustion of a fuel gas?

Accepted Answer

An adequate supply of air containing sufficient oxygen

Answer

A high concentration of carbon dioxide in the surrounding air

Answer

A low gas manifold pressure

Answer

A high ambient room temperature

Question 6

Gas appliances are classified into different venting categories. Which category describes a non-condensing appliance that operates with a non-positive (negative) vent pressure and uses a draft hood?

Accepted Answer

Category I

Answer

Category IV

Answer

Category III

Answer

Category II

A technician is servicing a natural draft gas furnace and observes soot buildup and discoloration around the burner area, indicating flame rollout.Which of the following is the MOST likely cause of this issue?

A technician is servicing a natural draft gas furnace and observes soot buildup and discoloration around the burner area, indicating flame rollout.
Which of the following is the MOST likely cause of this issue?