Oil Burner Nozzles: GPH, Angle and Pattern for Clean Combustion

An oil burner nozzle does one job other nozzles don’t: it atomises fuel so it burns. The droplet size decides whether the oil ignites clean or soots. The three numbers on the nozzle, GPH (gallons per hour), spray angle, pattern, are matched to the burner, and getting any one wrong means a smoky, inefficient flame.

The Selection Framework: Four Numbers

Every oil burner nozzle duty reduces to four numbers. Write them down before you touch a catalogue:

1. Firing rate (GPH): the gallons per hour the burner must fire. This sets the nozzle size and the pump.
2. Spray angle: the cone the combustion chamber can absorb. This sets the flame shape.
3. Pattern: hollow or solid cone. This matches the burner’s air design.
4. Fuel: #2 oil, bio-blend, or something heavier. This sets the material and the maintenance schedule.

A nozzle chosen without these four is a guess with a part number. With them, the selection is arithmetic.

Reference Table: GPH, Angle and Pattern

Our standard oil burner line, rated at 100 psi:

Model	GPH @ 100 psi	Angle	Pattern	Flow (L/h)	Connection	Material
BJ-OB0.5	0.5	60°	Hollow	~1.9	7/16-24	Brass
BJ-OB0.75	0.75	60°	Hollow	~2.8	7/16-24	Brass
BJ-OB1.0	1.0	60°	Hollow	~3.8	7/16-24	Brass
BJ-OB1.5	1.5	60°	Hollow	~5.7	7/16-24	Brass
BJ-OB2.0	2.0	60°	Hollow	~7.6	7/16-24	Brass
BJ-OB3.0	3.0	45°	Hollow	~11.4	7/16-24	Stainless
BJ-OB5.0	5.0	45°	Solid	~18.9	7/16-24	Stainless
BJ-OB10	10	45°	Solid	~37.9	7/16-24	Stainless

Flow conversions are approximate at 100 psi; exact flow is verified per batch. Bio-blends shift the number. Send your fuel spec for a real sizing.

GPH: The Fire Size

Gallons per hour is the fuel flow at the rated pump pressure (usually 100 psi). It sets how big the fire is:

• 0.5–2 GPH: domestic / small commercial burners.
• 2–10 GPH: commercial / industrial.
• 10+ GPH: large industrial, multiple nozzles.

The pump is sized to deliver the GPH at pressure; change the nozzle GPH and you change the fire. A nozzle rated 100 psi that sees 80 psi flows less. The fire shrinks and the pattern distorts.

Spray Angle: Flame Shape

The angle (usually 45°–80°) sets how the cone opens into the combustion chamber:

• 45°: tight, long flame for a deep chamber.
• 60°: general-purpose.
• 80°: wide, short flame for a shallow chamber.

Match the angle to the chamber geometry. Too narrow and the flame hits the far wall (soot, impingement); too wide and it fills a deep chamber poorly (incomplete burn).

Hollow vs Solid Cone

• Hollow cone: fuel on the rim, mixes with air from the centre. The default for most burners; good primary air entrainment.
• Solid cone: fuel across the whole circle, denser core. Used where the burner needs a concentrated flame.

The pattern is chosen by the burner’s air design. A hollow-cone nozzle on a burner built for solid, or vice versa, gives poor mixing → soot.

Atomisation and Soot

The nozzle must make droplets fine enough to vaporise in the flame. Too coarse → unburned oil → soot, smoke, stack loss. The fineness is set by the orifice and the pump pressure (higher pressure = finer). A worn orifice flows more and atomises worse → the flame soots even at the right GPH. Replace burner nozzles on a schedule; they wear like every other orifice.

Material and Fuel

• Brass traditional: machines well, fine for clean fuel oil.
• Stainless for bio-blends or corrosive additives.
• Ceramic orifice in abrasive blends.

For standard #2 fuel oil, brass is the boring right answer; for blends or wet fuel, stainless survives.

Troubleshooting

1. Sooty flame → worn orifice (coarse drops), or pressure sag. Replace nozzle, hold pump pressure.
2. Flame impinges wall → angle too narrow for chamber. Widen.
3. Incomplete burn → wrong cone pattern for the burner air. Re-spec.
4. Fire too small → pump pressure low, nozzle flows under GPH. Fix the pump.

How We Compare to the Catalogue Brands

The burner lines (Delavan, Danfoss, Monarch) publish GPH, angle and pattern per model at 100 psi. Our oil-burner nozzles track the same ratings. A 2 GPH 60° hollow cone flows what their equivalents do at rated pressure. What a buyer weighs is spare-nozzle stock, bio-fuel compatibility, and lead time. We publish GPH and angle so you match the burner exactly.

The Physics of Fuel Atomisation

An oil burner nozzle turns liquid fuel into a fine mist so it can burn fast and clean. The physics:

• Droplet size decides burn quality. Fine drops vaporise in the flame; coarse drops fall as soot or unburned oil. The nozzle’s orifice and pressure set the drop band.
• Pressure drives atomisation. Rated at 100 psi; higher pressure = finer drops. A pump that sags below rated coarsens the spray and soots the flame.
• Pattern shapes the flame. Hollow cone pulls air into the centre; solid cone keeps a dense core. The burner’s air register was designed for one of them. Mismatch soots.

Every sooty flame traces back to one of these three: worn orifice (coarse drops), sagging pump (low pressure), or wrong pattern (bad air mix).

Industry Applications: Where Oil Burner Nozzles Earn Their Keep

• Residential and light commercial heating: 0.5–1.5 GPH hollow cone; the classic boiler and furnace nozzle.
• Industrial process heat: 2–10 GPH; boilers, dryers, ovens; stainless for bio-blends.
• Waste oil burners: heavy, dirty fuel; larger orifice, higher pressure, stainless; filters are the maintenance story.
• Bio-diesel and blends: B5–B100; stainless or brass with more frequent replacement; the chemistry attacks brass over time.
• Multi-nozzle burners: staged firing; several nozzles in one head, each sized for a firing stage.

Each application is the same four numbers with a different answer set.

Worked Example

You run a 3 GPH burner, deep chamber, needs a tight flame.

1. GPH → 3 GPH at 100 psi pump. Size pump to hold 100 psi.
2. Angle → 45° for the deep chamber (long flame, no wall hit).
3. Pattern → hollow cone (burner air design).
4. Material → standard fuel oil → brass.

Clean flame, no soot, no impingement.

FAQ: Oil Burner Questions We Actually Get

Q: Why is my flame sooty even with a new nozzle? A: Pressure. The pump is sagging below 100 psi, so the spray coarsens. Check the pump and the pressure at the nozzle, not the gauge at the tank.

Q: How often should I replace the nozzle? A: Every season for residential; on inspection for industrial. The orifice erodes, flow rises, the flame soots. A nozzle is a wear part, not a fit-and-forget.

Q: Hollow or solid cone for my burner? A: Match the burner’s air design. Most burners run hollow cone; solid is for specific air registers. The burner manual says which. Trust it.

Q: Can I go up a GPH to get more heat? A: No. The nozzle size must match the burner and the chamber. Oversizing fires a bigger flame than the chamber and air register can handle, and the soot and efficiency loss cost more than the heat gained.

Q: Bio-fuel ok with a brass nozzle? A: Short term; the acids in bio-blends attack brass over time. Stainless for any bio blend you plan to run long-term.

Maintenance: What Kills an Oil Burner Nozzle

• Orifice erosion: the #1 killer. The hole enlarges, flow creeps up, the flame soots. Replace on schedule; check flow against the rating.
• Carbon build-up: a nozzle that runs rich or dirty cakes the tip; the pattern distorts. Clean or replace; fix the pressure that caused it.
• Clogging: dirty fuel or a dirty tank; the orifice sieges. Filter the fuel, keep the tank clean.
• Chemical attack: bio-blends corrode brass; stainless for blends.

An oil burner nozzle is a consumable. Schedule replacement. The soot and efficiency loss of a worn one costs more than the nozzle.

Selection Checklist (Print This)

• Firing rate (GPH) matched to the burner spec
• Spray angle chosen for the chamber geometry
• Pattern (hollow/solid) matched to the air register
• Pump holds 100 psi at the nozzle, checked, not assumed
• Material matched to fuel: brass for #2, stainless for bio-blends
• Spare nozzles on the shelf. It is a consumable

Atomisation, Soot and the Numbers That Bind Them

The nozzle’s droplet size is the bridge between “fuel in” and “heat out”:

• Fine drops (under ~100 µm): vaporise fast, ignite clean, release heat in the flame zone. This is the goal.
• Coarse drops (over ~200 µm): survive the flame, fall as soot or unburned oil. This is the failure.

What pushes the drop coarse: a worn orifice (flows more, atomises worse), low pressure (the pump sags), or the wrong pattern for the air. The three fixes are the same three numbers: GPH, angle, pattern, checked against the pump, not the spec sheet.

The Five Mistakes to Avoid

1. Oversizing GPH for “more heat”: the chamber and air register can’t absorb it; soot and inefficiency cost more than the heat gained.
2. Wrong angle for the chamber: a narrow cone in a shallow chamber impinges the wall; a wide cone in a deep chamber burns poorly.
3. Ignoring the pump: a sagging pump coarsens every nozzle. Check pressure at the nozzle, not the tank.
4. Brass on bio-blends: the acids attack it. Stainless for any long-term bio run.
5. Never replacing: a worn orifice soots quietly. Replace on schedule, not on failure.

Every one is a system error. Answer the four numbers and the five mistakes disappear.

The One-Paragraph Summary

An oil burner nozzle atomises fuel: size the GPH to the burner, match the angle to the chamber, match the pattern to the air register, keep the pump at 100 psi, choose the material for the fuel, and replace it on schedule, because the orifice wears and a worn nozzle soots even at the right GPH.

Flame Shape and the Chamber

The spray angle and pattern create the flame shape, and the flame must fit the chamber:

• Narrow angle (45°) in a deep chamber: a long, tight flame that travels and burns late. Right for a tall boiler.
• Wide angle (60–80°) in a shallow chamber: a short, bushy flame that burns fast. Right for a compact furnace.
• Impingement: a flame that hits the wall runs cool at the wall (wet soot) and hot in the gas stream. The nozzle angle was wrong for the chamber.

A burner nozzle that is “the same GPH” but the wrong angle changes the whole combustion. Match the angle to the chamber, not to the pump.

Installation: The Five-Minute Job Done Right

Replacing an oil burner nozzle is simple, and the details decide the season:

• Clean the burner head: carbon on the head distorts the new nozzle’s pattern. Wipe it.
• Torque the nozzle, don’t crush it: over-tightening distorts the orifice. Seat it snug, no more.
• Align the pattern: the nozzle’s slot or orientation matters on some burners. Match the old one’s position.
• Check the pump pressure: 100 psi at the nozzle, not just at the pump. A filter or a worn pump costs a season.
• Record the GPH and angle: the old nozzle’s numbers are the baseline; write them down before you throw it away.

Five minutes, and the burner runs the season.

What to Send a Supplier for a Quote

1. Firing rate: GPH, from the burner spec or the old nozzle.
2. Angle and pattern: from the burner manual; if unknown, the old nozzle’s markings.
3. Fuel: #2 oil, bio-blend, waste oil; blends change the material.
4. Pump pressure: what the pump actually holds at the nozzle.

With those four, the quote comes back with a model. Without them, every supplier picks blind.

Troubleshooting: The Full Walkthrough

When the burner misbehaves, walk this list:

1. Sooty flame, new nozzle: pressure. Check 100 psi at the nozzle; the pump or filter is the problem.
2. Sooty flame, old nozzle: wear. Flow-test the nozzle; replace if it flows over rating.
3. Flame impinges the wall: angle too narrow for the chamber. Widen.
4. Rough start or hunting: pattern wrong for the air register, or the nozzle is partially clogged. Check the pattern, clean or replace.
5. Oil smell in the house/plant: coarse drops falling unburned. Pressure, wear, or wrong pattern, in that order.

Ninety percent of burner complaints are the three numbers drifting: GPH, angle, pattern, or the pump behind them.

Material Selection and Fuel Compatibility

Fuel	Recommended nozzle material	Notes
#2 fuel oil	Brass	The default; cheap, machines well
B5–B20 bio-blend	Brass (short-term) / Stainless (long-term)	Acids attack brass over time
B100 / pure bio	Stainless	Aggressive chemistry
Waste/used oil	Stainless, larger orifice	Dirty fuel; filters are mandatory
Light kerosene	Brass	Low viscosity, fine atomisation easy

The fuel picks the material, and the maintenance schedule follows. A brass nozzle on B100 is a season-long gamble.

Staged Firing and Multi-Nozzle Burners

Large industrial burners don’t use one nozzle. They stage the fire with several:

• Pilot + main: a small nozzle lights the pilot, the big one takes the load. Each is sized for its stage.
• Modulating: two or three nozzles switch in stages (low/med/high) as the load demands. The GPH set is a ladder, not a single number.
• The trap: replacing “a nozzle” on a staged burner without noting which stage it was. Every stage has its own GPH/angle/pattern; mixing them wrecks the fire.

If the burner has more than one nozzle, record each position’s spec. The nozzle is not interchangeable with its neighbour.

Quick Reference: GPH to Heat

GPH @ 100 psi	Approx. heat (kW)	Typical use
0.5	~19 kW	Small residential
0.75	~28 kW	Residential
1.0	~38 kW	Residential / small commercial
1.5	~57 kW	Commercial
2.0	~76 kW	Commercial / light industrial
3.0	~114 kW	Industrial
5.0	~190 kW	Industrial process

Heat figures are approximate for #2 oil. The burner and chamber decide the actual firing rate. The nozzle follows the spec, not the other way.

The Bottom Line on the Flame

An oil burner nozzle is the cheapest part of the burner and the one that decides the season: size the GPH to the firing rate, match the angle to the chamber, match the pattern to the air register, keep the pump at 100 psi, pick the material for the fuel, and replace on schedule, not on failure. A worn or wrong nozzle soots quietly, wastes fuel, and costs more in a winter than it does to replace in five minutes.

When the Answer Is a Different Atomiser

A pressure nozzle is not the only way to atomise fuel. Air-atomising burners (compressed air or steam) handle heavy and waste oils that a pressure nozzle cannot; rotary cup atomisers handle the very heaviest. The pressure nozzle owns the clean, consistent fuel at moderate rates. Outside that, the atomiser changes, not the nozzle.

One Sentence Before You Spec

Tell the supplier the firing rate, the spray angle, the pattern, the fuel, and the pump pressure at the nozzle, and an oil burner nozzle spec writes itself. Withhold any one and you are gambling with the flame.

The Pressure Connection: 100 psi Is Not Optional

Every rating on the nozzle assumes 100 psi at the orifice. A burner running at 90 psi:

• Flows ~5% less (flow scales with √pressure), the fire shrinks quietly.
• Atomises coarser. The drops are bigger, the soot returns.
• Distorts the pattern. The cone opens differently than the chamber was designed for.

The pump and the line are part of the nozzle spec. Check the pressure at the nozzle with a gauge, once a season, and the nozzle does what the rating says. Skip it and every “bad nozzle” is really a bad pump reading.

The 30-Second GPH Pick

Burner type	Typical GPH	Pattern
Small residential boiler	0.5–0.75	Hollow 60°
Residential furnace	0.75–1.0	Hollow 60°
Small commercial	1.0–1.5	Hollow 60°
Commercial boiler	1.5–2.0	Hollow 60°
Industrial process	2.0–5.0	Hollow or solid 45°
Heavy industrial	5.0–10	Solid 45°

Thirty seconds to a starting point, then confirm against the burner manual and the old nozzle. The table narrows the search; the burner spec is the answer.

Bottom Line

An oil burner nozzle atomises fuel. GPH sets the fire size, angle sets the flame shape, hollow/solid cone sets the air mix. Match all three to the burner and hold pump pressure, or the flame soots and wastes fuel. Replace on schedule; a worn orifice soots even at the right GPH.

Need a nozzle matched to your burner? Browse the oil burner nozzle range or send your firing rate and chamber details via the enquiry form for a sizing. If a larger nozzle has already been fitted and the furnace is smoking, what an oversize oil burner nozzle does to a furnace explains the follow-on damage.