CCI Plumbing & Mechanical Systems 3 — Questions and Answers
Question 1: Under the IMC, what is the minimum clearance required between a gas-fired furnace and combustible construction?
- 0 inches if listed for zero clearance (Correct answer)
- 2 inches
- 6 inches
- 12 inches
Correct answer: 0 inches if listed for zero clearance
Appliances listed and labeled for zero clearance can be installed directly against combustible materials if installed per their listing and manufacturer instructions.
Question 2: Which venting method uses a single pipe that serves as both the supply air and the vent for a high-efficiency furnace?
- Category I venting
- Direct vent (two-pipe) system (Correct answer)
- Power-vent system
- Atmospheric venting
Correct answer: Direct vent (two-pipe) system
A direct vent system uses two pipes: one to draw combustion air from outside and one to exhaust flue gases, making it a sealed combustion system.
Question 3: An inspector observes that a mechanical room housing a boiler has no means of combustion air. The correct remedy is to:
- Install a make-up air louver or duct sized per code (Correct answer)
- Add a CO detector and leave as-is
- Install an exhaust fan to draw in fresh air
- Seal all gaps to prevent back-drafting
Correct answer: Install a make-up air louver or duct sized per code
Combustion air must be provided to fuel-burning equipment rooms via louvers, ducts, or openings sized according to the fuel input BTU rating per the IMC.
Question 4: What material is NOT permitted for use as a gas supply piping in residential construction per the IFGC?
- Black steel pipe
- CSST (corrugated stainless steel tubing)
- Copper tubing (Type K or L)
- PVC plastic pipe (Correct answer)
Correct answer: PVC plastic pipe
PVC plastic pipe is not approved for gas supply piping; approved materials include steel, copper, CSST, and PE pipe in limited applications.
Question 5: What is the required minimum distance between a gas appliance vent termination and a window or door opening per the IFGC?
- 1 foot
- 2 feet
- 3 feet (Correct answer)
- 6 feet
Correct answer: 3 feet
The IFGC requires vent terminations to be at least 3 feet from any openable window, door, or gravity air inlet to prevent re-entry of combustion gases.
Question 6: A drain, waste, and vent (DWV) system air test is performed by pressurizing the system to:
- 5 psi for 15 minutes (Correct answer)
- 10 psi for 15 minutes
- 15 psi for 15 minutes
- 25 psi for 10 minutes
Correct answer: 5 psi for 15 minutes
Per the IPC, an air test for DWV systems requires pressurization to 5 psi with air or nitrogen, maintained for at least 15 minutes without pressure loss.
Question 7: Which type of pipe fitting is required when changing direction in a drainage system from vertical to horizontal?
- 90-degree elbow
- Long-sweep 1/4 bend (Correct answer)
- Standard tee
- Sanitary cross
Correct answer: Long-sweep 1/4 bend
Long-sweep fittings (long-turn 1/4 bends) are required at vertical-to-horizontal transitions in drainage systems to maintain flow velocity and prevent solids buildup.
CCI Plumbing & Mechanical Systems 3
Under the IMC, what is the minimum clearance required between a gas-fired furnace and combustible construction?