Practice Test Geeks(FC) Furnace Installation and Maintenance Certification Practice Test

FC Cheat Sheet 2026

The 30 highest-yield FC facts, distilled from real exam questions. Print it, save it as a PDF, or study it here β€” free, no sign-up.

100 questions
180 min time limit
70.00% to pass
  1. What is the purpose of the dielectric union required when connecting a gas furnace to the gas supply piping that contains dissimilar metals? β†’ To prevent galvanic corrosion between dissimilar metals
  2. When performing a combustion analysis on a high-efficiency condensing furnace, a technician finds excess air is very high. This indicates: β†’ Air is infiltrating the combustion system, diluting flue gases and reducing efficiency
  3. When installing a Category IV (positive pressure, condensing) vent system, which vent pipe material is required? β†’ PVC or CPVC plastic pipe
  4. What can cause a heating system to blow cold air instead of warm air? β†’ The furnace is malfunctioning or lacks sufficient fuel
  5. Why is it important to check the air filters during heating system maintenance? β†’ To ensure efficient airflow and prevent overheating
  6. The sensible heat ratio (SHR) is most relevant when evaluating a furnace's: β†’ Interaction with a cooling coil in a combined HVAC system
  7. What is the first step in troubleshooting a heating system? β†’ Inspect the furnace and check for obvious issues
  8. A technician is performing a combustion analysis and finds CO in the flue gas at 1,200 ppm air-free. What does this indicate? β†’ Incomplete combustion, likely from insufficient primary air or a cracked heat exchanger
  9. What is the minimum clearance required between a furnace and combustible materials on the sides, unless the manufacturer specifies otherwise? β†’ 1 inch
  10. Static pressure in the duct system is important for efficiency because excessively high static pressure causes: β†’ The blower motor to work harder, consuming more electricity and reducing airflow
  11. What does the 99% outdoor design temperature represent in a heating load calculation? β†’ The temperature that is equaled or exceeded only 1% of the hours in the heating season
  12. What is the purpose of the pressure switch on an induced-draft furnace? β†’ To confirm the inducer motor is creating proper draft before allowing ignition
  13. What is the minimum upward slope required for horizontal sections of Category I single-wall vent connector pipe? β†’ 1/4 inch per foot rise toward the chimney or vertical vent
  14. A technician finds a cracked heat exchanger in a gas furnace. According to industry safety standards, what is the REQUIRED action? β†’ Tag the unit out of service and inform the owner immediately
  15. What is the purpose of the concentric vent system on a direct-vent condensing furnace? β†’ To use one pipe for exhaust and a surrounding outer pipe for combustion air intake
  16. What is the required clearance around a furnace as per safety standards? β†’ There should be a specified clearance based on the manufacturer’s guidelines
  17. A furnace ignites but the flame shuts off after 8–10 seconds. The most probable cause is: β†’ Failed flame sensor (dirty or corroded)
  18. Which test method uses a chemical tracer gas introduced into the combustion side to detect heat exchanger cracks? β†’ Tracer gas leak test (e.g., nitrogen with halide detector)
  19. Which type of ignition system uses a resistance element heated to approximately 1,800Β°F to ignite the gas? β†’ Hot surface igniter
  20. What is the maximum recommended oversizing percentage for a gas furnace according to ACCA Manual S guidelines? β†’ 40%
  21. Which duct system characteristic most significantly reduces overall HVAC system efficiency? β†’ Leaky ducts located in unconditioned spaces like attics or crawlspaces
  22. A Category IV furnace vents with positive pressure and produces condensate. Which vent material is specifically listed for this application? β†’ Listed PVC or CPVC vent pipe
  23. According to the IMC, what is the minimum chimney height above the roof for a masonry chimney serving a gas furnace? β†’ 2 feet above the highest point within 10 feet horizontally
  24. Why is it important to use an energy-efficient furnace? β†’ To lower energy costs and environmental impact
  25. Which maintenance task has the greatest direct impact on maintaining a gas furnace's rated AFUE over time? β†’ Cleaning the heat exchanger and burners to remove scale and debris
  26. When adding a new supply run to an existing duct system, what must be verified to prevent degrading other rooms? β†’ That the existing system has sufficient blower capacity to handle the added airflow load
  27. Which code section addresses combustion air requirements for gas furnaces installed in confined spaces? β†’ NFPA 54 Chapter 9
  28. What does 'design temperature difference' (Ξ”T) mean in the context of heating load calculations? β†’ The difference between indoor design temperature and outdoor design temperature
  29. How do you maintain the furnace blower motor? β†’ Lubricate, inspect, and ensure proper alignment
  30. What is the recommended maximum number of 90-degree elbows allowed in a standard PVC vent run for a condensing furnace before derating the allowable length? β†’ 3
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