HVAC Excellence Oil Heat Certification Exam flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Nozzle gph rating

Gallons per hour of No. 2 oil the nozzle passes at 100 psi; multiply by about 140,000 Btu/gal to get burner input. A 0.85 gph nozzle fires roughly 119,000 Btu input.

Nozzle spray angle

The cone angle of the oil spray, commonly 45° to 80°. Narrow angles suit long, narrow combustion chambers; wider 70°–80° angles suit short, round chambers to avoid impingement.

Solid vs hollow cone

Solid-cone nozzles produce a filled spray pattern used with retention-head burners; hollow-cone nozzles produce a ring pattern used with conventional burners. Matching pattern to burner type prevents pulsation and soot.

Pump pressure 100 psi

Standard residential oil burner pump discharge pressure. It sets atomization quality and nozzle flow; raising to 140 psi increases flow about 18% and is used only where the burner manufacturer allows.

Two-pipe oil system

Supply and return lines from tank to pump, with the return bypassing unused oil back to the tank. Used when the tank is below the burner or the run is long, to prevent air lock and vacuum problems.

Single-pipe oil system

One supply line from a tank above the burner; oil flows by gravity and the pump's internal bypass returns excess to the nozzle line. Requires a tank higher than the burner and a properly sized line.

Oil filter location

Installed in the supply line between tank and burner, often at the tank outlet or near the burner. A clogged filter causes low pump pressure, delayed ignition, and lockout; replace at annual service.

Cad cell resistance

Flame detector whose resistance drops from over 50,000 Ω dark to roughly 300–1,500 Ω in flame light. The primary control uses this change to prove flame and prevent lockout.

Primary control lockout

Safety shutdown when the cad cell does not sense flame within the trial-for-ignition period (typically 15–45 s). The control stops the burner and often requires manual reset.

Trial for ignition

Time the primary control allows for flame establishment after the burner starts, usually 15–45 seconds. If no flame is proven, the control locks out and shuts off the oil valve.

Electrode spark gap

Distance between electrode tips, typically 1/8–3/16 in. Too wide weakens the spark; too narrow causes carbon bridging. Set per burner manufacturer's label and check with a gauge.

Electrode position above nozzle

Typical retention-head setting: tips 1/8–5/32 in. above nozzle centerline and 1/16–1/8 in. ahead of the nozzle face. Misalignment causes delayed ignition and puff-back.

Retention head burner

Burner with a shaped head that stabilizes flame and improves mixing; uses solid-cone nozzles and higher CO₂ (11.5–13.0%). Requires correct head setting and clean air passages.

Conventional burner

Older burner design without a retention head; uses hollow-cone nozzles and lower CO₂ (about 9.5–11.5%). Flame shape depends on chamber and draft; less efficient than retention-head types.

Overfire draft

Negative pressure in the combustion chamber, typically −0.02 to −0.04 in. w.c. for natural-draft oil equipment. It pulls combustion gases through the heat exchanger and up the flue.

Breach draft

Draft measured in the flue connector between appliance and chimney, typically −0.02 to −0.04 in. w.c. It confirms the chimney is pulling; positive reading means blockage or inadequate chimney.

CO₂ target range

For retention-head oil burners, 11.5–13.0% CO₂ with smoke 0–1. Higher CO₂ means less excess air and better efficiency but risks smoke; adjust air shutter to the highest CO₂ without smoke.

Smoke test number

Bacharach smoke spot number from 0 (clean) to 9 (heavy soot). Oil burners should run at 0–1; a reading of 2 or higher indicates poor combustion and requires adjustment.

Net stack temperature

Stack temperature minus room temperature. Used with CO₂ and smoke to estimate steady-state efficiency; high net stack temperature (above about 500°F) signals a fouled heat exchanger.

Steady-state efficiency

Combustion efficiency calculated from CO₂, stack temperature, and net stack temperature using a slide rule or analyzer. Typical oil equipment runs 80–86%; below 78% indicates cleaning or adjustment needed.

AFUE

Annual Fuel Utilization Efficiency, the seasonal efficiency rating for furnaces and boilers. Modern oil equipment ranges about 80–87% AFUE; older units may be 70–75%.

Combustion air requirement

About 10 ft³ of air per ft³ of oil burned, plus excess air. A confined boiler room needs dedicated louvers sized per code; insufficient air causes CO production and soot.

Barometric draft regulator

Damper in the flue connector that opens to admit room air and holds a steady negative draft. It compensates for chimney variations and prevents excessive draft from cooling the appliance.

Flue gas spillage

Combustion products escaping into the room instead of up the chimney, caused by blocked flue, reversed draft, or inadequate chimney. Detect with a draft gauge or smoke pencil at the relief opening.

Oil tank gauge

Float gauge on the tank showing approximate oil level. A stuck or inaccurate gauge causes runouts; verify by dipping the tank or comparing gauge reading to actual consumption.

Oil tank vent pipe

Pipe from tank to outdoors that lets air in as oil is drawn out and relieves pressure. It must slope back to the tank and be clear; a blocked vent causes slow flow or tank collapse.

Oil tank fill pipe

Pipe with a capped fill opening, typically 2 in., sloped toward the tank. It must be distinct from the vent and marked; cross-connection causes overfill and spill.

Oil line vacuum test

Checking pump inlet vacuum with a gauge; typically should not exceed 10–12 in. Hg. High vacuum indicates a clogged filter, kinked line, or restricted tank outlet.

Delayed ignition

Oil ignites late after burner start, causing a puff or rumble. Causes include weak spark, wrong electrode setting, low pump pressure, or dirty nozzle; correct before operation.

Puff-back

Explosive ignition of accumulated oil vapor in the combustion chamber. Often from delayed ignition, wrong nozzle, or blocked flue; can damage the appliance and is a safety hazard.

Nozzle clogging

Dirt or carbon blocking the nozzle orifice, causing poor spray, low firing rate, and smoke. Replace the nozzle at annual service; never clean or drill the orifice.

Oil burner transformer

Step-up transformer supplying 10,000–15,000 V to the electrodes for ignition. A weak transformer causes hard starting and delayed ignition; test spark and voltage per manufacturer.