Oil Burner and Combustion Components
Oil Burner and Combustion Components
This domain tests burner anatomy and the combustion chain: oil storage and delivery, filtration, pump pressure, atomization, ignition, flame detection, draft, and air adjustment. Expect component-function items and a sequence-of-operation question.
Core rules
- The oil pump draws through a filter and raises pressure, commonly 100–140 psi residential; excess oil returns or bypasses. Nozzle flow ratings are stated at 100 psi.
- The nozzle atomizes oil; size sets firing rate and pattern/angle must match the combustion chamber. A clogged nozzle causes delayed ignition, soot, or puffback.
- Electrode gap and position follow the manufacturer; too wide stresses the transformer, too narrow or oily causes hard starts.
- The cad cell detects flame; light lowers its resistance. The primary control provides pre-purge, trial for ignition, lockout, and post-purge.
- Draft is controlled by the chimney, connector, and barometric damper; too little air causes smoke and CO, too much air cools the flame and lowers efficiency.
Worked example
A 0.85 gph nozzle is rated at 100 psi, but the pump is set to 140 psi. Flow changes with the square root of pressure: √(140/100)=1.183, so actual flow is 0.85×1.183=1.006 gph. At about 140,000 Btu/gal, input is roughly 140,800 Btu/h, not 119,000 Btu/h. Recheck the nozzle selection, air setting, and combustion test rather than assuming the stamped rating.
Traps
Do not size a nozzle from pump pressure without correcting flow; do not change spray angle casually; do not set electrodes by eye; never bypass the cad cell; and do not adjust air without a smoke and draft test.