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These 10 free 6149 questions are organized by exam domain, so you can see how each part of the Master Oil Heat Specialist Certification (6149) blueprint is tested. Reveal the answer and explanation under each question.
Commissioning instructions specify approximately 0.80 U.S. gal/h actual oil delivery at 150 psi, using an 80-degree hollow-cone spray. Available replacement nozzles carry flow ratings at 100 psi. Chamber pressure is negligible compared with nozzle pressure. Select the Delavan nozzle that satisfies both the delivery and spray requirements.
Correct answer: D - 0.65 gal/h, 80-degree Type A.
An oil burner with a GeniSys 7505 primary control is correctly wired for interrupted ignition. It lights promptly. After flame establishment and the ignition carryover period, the igniter loses power, but the motor, oil valve, and stable flame remain on. The flame indicator stays steady, and combustion measurements meet the appliance requirements. How should the technician respond to the missing spark?
Correct answer: C - Leave the ignition operation unchanged; this is the expected run sequence.
One fuel line runs from the storage tank to a Tigerloop deaerator. Separate supply and return hoses connect the deaerator to a Beckett CleanCut fuel unit. An installer argues that the single tank line makes this a one-pipe pump installation. How must the fuel unit be configured for the piping described?
Correct answer: D - Install the bypass plug and retain both hoses to the deaerator.
A dual-fuel installation is programmed to use oil heat below 35°F and the heat pump at 35°F or above, with simultaneous operation prohibited. During a heat call, the controller displays 43°F and commands only the heat pump. A calibrated thermometer beside the shaded outdoor sensor reads 27°F after stabilization. Each heat source operates correctly when individually commanded for testing. Which component deserves attention before changing either heat source?
Correct answer: A - The outdoor-temperature sensing circuit.
At the doorway of a service call, a technician hears a CO alarm sounding. One resident has a headache and another feels nauseated. Both are still inside, and the oil furnace is running. The homeowner asks the technician to find the leak before involving anyone else. What takes priority at this point?
Correct answer: C - Get everyone outside to fresh air and call 911 from safety.
Inspection confirms a hole through the metal wall separating an oil furnace's combustion passage from its circulating-air stream. Ambient CO was 0 ppm during the brief operating test. The homeowner offers to install an additional CO alarm and asks to keep the furnace running until the replacement part arrives. Which disposition is defensible?
Correct answer: D - Keep the furnace out of service until approved repair or replacement is completed.
A burner begins to lose flame after several minutes of operation. Under the same steady-flow conditions, a vacuum gauge reads 2 inHg immediately before the oil filter and 9 inHg immediately after it. The test ports are at the same elevation, and the filter is the only component between them. Tank level and fuel temperature have not changed. Which fault best fits the pressure pattern?
Correct answer: B - Excessive restriction through the filter assembly.
The burner motor hums instead of accelerating. During a qualified live-voltage test, incoming power remains at 120 V to a verified neutral. The motor relay is fully pulled in, yet a measurement directly across its closed contacts reads 38 V while the motor attempts to start. With power isolated, the motor and pump turn freely. The measurements localize the voltage loss to:
Correct answer: A - Excessive resistance at the motor relay contacts.
Reviewing a saved oil-burner combustion test, a technician notices that the analyzer was set to natural gas. This instrument has direct O2 and CO sensors but no CO2 sensor. Its temperature probes, calibration, and sampling system checked correctly. Which pair of displayed results depends on correcting the fuel selection?
Correct answer: A - Calculated CO2 and combustion efficiency.
An appliance's service specification permits no more than 100 ppm CO on an air-free basis. At steady firing, a valid undiluted flue sample gives 90 ppm uncorrected CO and 8.0% O2; the smoke number is zero. Using 20.9% as the oxygen concentration in fresh air, how should these combustion results be classified?
Correct answer: B - About 146 ppm air-free CO; the CO requirement is not met.
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