Atomization, combustion and draft must be evaluated together
A pressure-atomizing oil burner prepares liquid fuel for combustion by producing a controlled spray. Small droplets provide a large surface for heating, evaporation and mixing with air. The nozzle’s nominal flow is only one part of its identity: the reference pressure, spray angle and distribution pattern also matter. The burner head and chamber must match that spray. A nozzle that fits the adapter or carries the right flow number can still be wrong for the appliance. Use the approved combination rather than selecting by appearance.
Pressure changes affect delivery. A nozzle rating applies at its stated reference condition, and a different pump pressure can change the firing rate. In a simplified exercise, a square-root pressure-flow relationship may be supplied; use that stated relationship without treating its numerical example as a field setting. Oil viscosity and temperature also affect the system, especially during cold starts. Fine internal passages require clean handling. Damage to the nozzle outlet is not corrected by an arbitrary air-shutter adjustment.
Reliable ignition needs the intended spray, air pattern and spark geometry at the correct time. Electrode position and insulation must match the burner specification. Poor ignition can permit an abnormal fuel accumulation, so an unexplained bang or repeated lockout is not a reason to keep trying. At shutdown, abnormal afterdrip can involve the fuel unit, trapped air or temperature-related effects in the nozzle line. Follow the appropriate diagnostic process rather than assume the electrical command proves that all fuel movement has stopped.
Assess combustion with the prescribed observations and instruments. Smoke indicates a condition requiring interpretation, not one uniquely failed part. A bright or apparently clean flame does not quantify carbon monoxide. Correct sample placement, analyzer condition and the reporting basis matter. Too little effective air or poor mixing can create deposits, but maximum air is not automatically optimum: excessive air can increase heat carried away through the vent.
Draft links the burner to the appliance, chimney and building. Natural buoyancy must overcome resistance and any competing pressure effects. Overfire and breech readings are different test locations. A barometric regulator must be installed and set for the approved arrangement, not used to hide an unsuitable chimney. Restore covers, baffles and air-intake components before final verification, because changing the assembled airflow path can change the conditions under which the burner was adjusted.