HVAC Excellence Oil Heat Certification Exam key terms

A precision orifice at the burner that meters oil flow and shapes the spray pattern. Its stamped rating, in gallons per hour at a stated pressure, sets the firing rate.

The heat input of an oil burner, usually expressed in gallons per hour of oil or BTU per hour. It is calculated from nozzle size and adjusted pump pressure.

The cone angle of the oil spray leaving the nozzle, commonly 70 to 90 degrees. It must match the combustion chamber shape so oil does not impinge on walls.

The distribution shape of atomized oil from a nozzle, such as solid, hollow, or semi-solid. Pattern choice affects flame shape and mixing with combustion air.

Breaking liquid oil into fine droplets so it vaporizes and mixes with air quickly. Poor atomization causes smoky combustion, delayed ignition, and unstable flame.

The pressure, in psi, delivered by the fuel unit to the nozzle, typically 100 psi. Changing pressure alters flow rate and spray quality, so it must be set to the appliance rating.

The oil pump mounted on the burner that draws oil from the tank, pressurizes it, and delivers it to the nozzle. It may include a pressure regulator and cut-off valve.

A screw or port on the fuel unit used to purge trapped air from the oil line while the burner runs. Air in the line causes pulsating pressure and rough starts.

A fuel oil piping arrangement where a single line carries oil from the tank to the burner, with return oil handled internally by the fuel unit. Used when the tank is above the burner.

A fuel oil piping arrangement with separate supply and return lines between tank and burner. It allows greater lift, easier air removal, and more reliable delivery in difficult installations.

The vertical distance oil must be raised from the tank outlet to the fuel unit. Excessive lift can cause cavitation, loss of pressure, and burner lockout.

A trapped pocket of air in the oil supply line or fuel unit that blocks oil flow. Symptoms include no flame, pressure fluctuation, and repeated burner shutdowns.

A device in the fuel line that removes dirt, rust, and sludge before oil reaches the fuel unit. A clogged filter reduces pressure and can cause nozzle plugging.

Thick sediment that forms in oil tanks from water, microbial growth, and aged fuel. It can clog filters and lines and should be removed by tank cleaning or fuel polishing.

Moisture that collects at the bottom of a tank and promotes corrosion, sludge, and burner problems. It is removed by draining the tank or using a water-absorbing filter.

A liquid petroleum distillate used for heating, commonly No. 2 heating oil. Its properties include viscosity, sulfur content, and heating value, which affect combustion and equipment.

The refractory-lined or metal space where fuel and air burn. Its size and shape must match the burner's spray pattern for complete combustion and stable flame.

Heat-resistant material lining the combustion chamber that protects the appliance and helps maintain ignition temperature. Cracks or spalling can cause smoke and efficiency loss.

The ability of a burner to keep the flame anchored at the burner head under varying conditions. It depends on air velocity, head design, and chamber pressure.

The assembly at the end of the burner that mixes oil spray with combustion air and stabilizes the flame. Its position and adjustment strongly affect combustion quality.

The air supplied to the burner for burning fuel, controlled by the air shutter or damper. Too little causes smoke; too much cools the flame and lowers efficiency.

Air supplied beyond the theoretical amount needed for complete combustion, expressed as a percentage. It ensures complete burning but excessive amounts reduce efficiency.

A test that draws a sample of flue gas through filter paper to measure smoke density on a scale. It confirms clean combustion and proper air-to-fuel ratio.

The percentage of fuel heat released that is usefully transferred, reduced mainly by excess air and stack losses. It is calculated from flue gas temperature, oxygen or CO2, and ambient temperature.

The temperature of flue gases leaving the appliance, used with combustion readings to estimate efficiency. High stack temperature suggests heat exchanger fouling or excessive draft.

The negative pressure that moves combustion gases through the appliance and up the chimney. Proper draft prevents spillage of flue gases and supports stable combustion.

A hinged plate in the flue connector that regulates draft by admitting room air. It stabilizes draft over firing and weather changes and must be set with a draft gauge.

The passage that carries combustion gases from the appliance to the outdoors. Its size, slope, and condition affect draft and safe venting of products of combustion.

A vertical venting structure that creates draft and exhausts flue gases above the roof. It must be sized, lined, and maintained to prevent condensation and draft problems.

Metal rods that create a high-voltage spark to ignite the oil-air mixture. Their gap, position, and cleanliness are critical for reliable light-off.

A device that steps up voltage to create the spark at the electrodes. Weak or intermittent spark causes delayed ignition, puffback, or no heat.

A light-sensitive resistor that detects flame in the burner and signals the primary control. A dirty or failed cad cell can cause nuisance lockouts.

The burner's main safety control that supervises ignition, flame sensing, and shutdown. It enforces a timed trial for ignition and locks out if no flame is proven.

A safety shutdown in which the primary control stops the burner after failing to prove flame within the allowed time. It requires manual reset and correction of the cause.

A sudden explosion of unburned oil vapor in the combustion chamber, often caused by delayed ignition. It can damage the appliance and spread soot through the building.

The metal surfaces that transfer heat from combustion gases to the air or water being heated. Cracks or soot buildup reduce efficiency and can allow flue gases into the space.

The storage vessel for heating oil, typically steel or polyethylene, with fill, vent, gauge, and outlet connections. Proper support, venting, and leak protection are required.

A device that stops oil flow if the supply line loses pressure or the burner shuts down. It protects against siphoning and uncontrolled oil release.

An electronic instrument that measures oxygen, carbon dioxide, carbon monoxide, and flue temperature to calculate efficiency. It helps technicians tune the burner for clean, economical operation.