NATE Oil Heating 2 — Questions and Answers
Question 1: What does a #2 fuel oil supply line's two-pipe system accomplish compared to a single-pipe system?
- Increases oil flow rate to the burner
- Returns unused oil to the tank, preventing vapor lock and allowing the tank to be below the burner (Correct answer)
- Filters water from the oil supply
- Provides redundancy if the primary supply fails
Correct answer: Returns unused oil to the tank, preventing vapor lock and allowing the tank to be below the burner
A two-pipe system continuously circulates oil back to the tank, preventing air and vapor buildup and allowing a below-burner tank installation.
Question 2: What is the purpose of the electrodes in an oil burner?
- Sense the flame via rectification
- Produce a high-voltage spark to ignite the atomized oil-air mixture (Correct answer)
- Control oil pump speed
- Measure flue gas temperature
Correct answer: Produce a high-voltage spark to ignite the atomized oil-air mixture
Electrodes are positioned in the air-oil spray and produce a continuous or intermittent spark to ignite the mixture at startup.
Question 3: What condition does a high CO2 reading combined with a high smoke number indicate on a combustion analysis?
- Too much combustion air (lean mixture)
- Too little combustion air (rich mixture causing incomplete combustion) (Correct answer)
- Perfect combustion efficiency
- Low oil pump pressure
Correct answer: Too little combustion air (rich mixture causing incomplete combustion)
High CO2 with high smoke indicates insufficient air, producing a rich mixture with incomplete combustion and carbon soot.
Question 4: What is the function of the delayed oil valve (solenoid valve) on some oil burners?
- Prevent oil flow during power outages
- Stop oil flow immediately on burner shutdown to prevent after-drip and after-fire (Correct answer)
- Regulate oil pressure during high-fire mode
- Allow oil to flow only on a call for heat
Correct answer: Stop oil flow immediately on burner shutdown to prevent after-drip and after-fire
The delayed oil valve closes instantly when the burner shuts off, preventing oil drip into the combustion chamber that could cause after-fire and smoke.
Question 5: What is a puffback in an oil heating system?
- Small backfire explosion caused by igniting accumulated unburned oil in the combustion chamber (Correct answer)
- Reverse airflow through the flue
- Oil pump pressure surge
- Excessive combustion air condition
Correct answer: Small backfire explosion caused by igniting accumulated unburned oil in the combustion chamber
A puffback occurs when oil mist accumulates before ignition and ignites suddenly, causing a small explosion that can spread soot throughout the home.
Question 6: What percentage of CO2 in flue gas typically represents near-ideal combustion for a #2 oil burner?
- 5–7%
- 8–10%
- 11–13% (Correct answer)
- 15–17%
Correct answer: 11–13%
CO2 levels of 11–13% indicate near-stoichiometric combustion with minimal excess air and good efficiency for #2 fuel oil.
NATE Oil Heating 2
What does a #2 fuel oil supply line's two-pipe system accomplish compared to a single-pipe system?