HVAC Excellence Oil Heat Certification key terms

The standard light heating oil used in most residential oil burners; it flows readily, ignites easily when atomized, and carries roughly 138,000 to 140,000 Btu per gallon.

A measure of how thick or resistant to flow a liquid is. Oil viscosity rises as temperature falls, which affects pump performance, atomization quality, and whether a preheater is needed.

Breaking liquid fuel into a fine mist so it can mix with air and burn cleanly. Poor atomization produces smoke, soot, delayed ignition, and lower efficiency.

The device at the burner head that atomizes oil at a rated flow in gallons per hour and a specified spray angle and pattern, matched to the appliance's firing rate and combustion chamber.

The cone width of the oil mist leaving a nozzle, commonly 70 to 90 degrees. It must suit the combustion chamber shape so the flame does not impinge on walls or short-circuit.

The fuel input of a burner expressed in gallons per hour, converted to Btu per hour for sizing. It must fall within the appliance's approved range and match the nozzle installed.

Two metal points at the burner head that create a spark to light the oil mist. Their gap, position, and cleanliness are critical to reliable ignition.

A step-up transformer supplying high voltage, typically 10,000 volts or more, to the electrodes so a spark jumps the gap and ignites the atomized oil.

A light-sensitive resistor that detects flame in the combustion chamber. Its resistance drops sharply in the presence of flame, and the primary control uses that change to prove combustion.

The burner's main safety and operating control. It runs the burner motor, ignition, and oil valve, monitors the cad cell, and shuts the burner down if flame is not proven in time.

The safety function that confirms a flame exists during the trial-for-ignition period and throughout operation, then shuts off fuel if the flame fails, preventing unburned oil from accumulating.

The timed period after fuel and spark begin during which the control waits for the cad cell to see flame. Failure within that window sends the burner into lockout.

A safety shutdown in which the primary control stops the burner and holds it off after a failed flame-proving attempt. The control usually must be manually reset before operation resumes.

A condition where oil enters the chamber but ignites late, causing a puff, rumble, or puffback. Causes include weak spark, wrong electrode setting, or poor atomization.

A sudden explosion of unburned oil vapor in the combustion chamber that forces soot and smoke out of the appliance. It signals an ignition or fuel-delivery fault that must be corrected.

The air supplied to the burner to mix with atomized oil and support burning. Too little causes smoke and carbon monoxide; too much wastes heat up the flue.

The air supplied beyond the theoretical amount needed for complete combustion, expressed as a percentage. Some excess is required for clean burning, but too much lowers efficiency.

The negative pressure that pulls combustion gases through the appliance and up the chimney. Adequate, stable draft is required for safe venting and proper burner operation.

A hinged flap in the flue connector that opens to admit room air and stabilize draft. Correct adjustment keeps over-fire draft steady and prevents excess air from being pulled through the appliance.

The passage that carries combustion gases from the appliance to the outdoors. Its size, slope, and condition affect draft, safety, and the risk of spillage into the building.

The temperature of gases leaving the appliance. Comparing it with room or combustion air temperature indicates heat lost up the chimney and helps calculate combustion efficiency.

The percentage of fuel heat that is actually released and usefully transferred, determined from flue gas temperature, oxygen or carbon dioxide content, and net stack loss.

A procedure that pulls a measured sample of flue gas through filter paper and compares the stain to a standard scale to judge how completely the oil is burning.

Carbon residue left by incomplete combustion. It insulates heat exchanger surfaces, reduces efficiency, and can foul the burner and flue if not cleaned.

The refractory-lined space where atomized oil and air burn. Its size and shape must match the nozzle spray pattern and firing rate to avoid flame impingement and incomplete burning.

Heat-resistant material lining the combustion chamber that withstands high temperatures and radiates heat back to help ignite and stabilize the flame.

The condition where the flame touches the chamber walls or heat exchanger surfaces, causing soot, carbon buildup, and possible damage. It usually indicates a mismatched nozzle or misaligned burner.

The assembly that pumps, atomizes, and ignites fuel oil and mixes it with air. Common residential types include the retention-head and flame-retention burners.

The burner component that draws oil from the tank and delivers it to the nozzle at the required pressure, often through a filter and shutoff valve.

The oil pressure delivered to the nozzle, typically around 100 psi for residential burners. It directly affects atomization quality and the actual firing rate.

An electrically operated valve on the fuel pump that opens to admit oil at burner start and closes to cut it off at shutdown, helping prevent afterfire and delayed ignition.

Combustion that continues or flares after the burner has shut off, often due to a leaking valve or nozzle. It wastes fuel and can damage the appliance.

A strainer or cartridge that removes dirt and sediment from fuel before it reaches the pump and nozzle, protecting small passages from clogging.

The storage vessel for heating oil, typically steel or fiberglass and often located indoors or buried. It must be properly vented, supported, and protected against leaks.

The piping that carries oil from the tank to the burner. It may be a single-pipe or two-pipe arrangement, and air leaks or restrictions cause poor performance.

The metal surfaces that transfer heat from combustion gases to the air or water being heated. Soot or cracks on these surfaces reduce efficiency and can be a safety hazard.

The total heat released by burning a fuel, including the latent heat in the water vapor produced. Efficiency ratings may use either gross or net values, so comparisons must be consistent.