Changing Fuel Oil Furnace Nozzle: Step-By-Step Guide

Changing the nozzle on a fuel oil furnace is a complex task that requires careful consideration of several factors. The nozzle's size, pattern, and angle must be compatible with the furnace's specifications, as an incorrect match can lead to improper combustion, sooty operation, and even safety hazards. The nozzle's flow rate, spray pattern, and spray angle need to align with the combustion chamber's design and shape. A longer combustion chamber typically uses a more narrow spray angle, while a shorter chamber requires a wider angle.

It is also important to note that modern high-speed oil burners require specialized equipment and training to adjust and fine-tune properly. Homeowners without the necessary tools and expertise risk improper operation, soot buildup, and even a puffback explosion. Therefore, it is generally recommended to consult a trained service technician for assistance in selecting and installing the appropriate nozzle for your fuel oil furnace.

The nozzle size in gallons per hour (GPH) should be within the manufacturer's recommended range

The nozzle size is rated by GPH (gallons per hour of fuel use), spray angle, and spray pattern. For example, a .60 80 B nozzle will deliver .6 GPH oil use with an 80-degree angle and solid spray. You may experiment with a smaller GPH nozzle to achieve better fuel economy. For instance, a 1.20 GPH nozzle may be replaced with a 1.10 GPH, etc.

The nozzle size in GPH can also be calculated using the following formula: Firing rate = boiler input in BTUH divided by 140,000 (the heat content of #2 fuel oil in BTU per gallon). This will give you the nozzle GPH. Nozzles are typically rated at 100 psi, so check your pump pressure.

It is important to note that changing the spray angle of the nozzle should be left to an experienced technician. A change in the oil burner spray angle is potentially a more serious error as it may result in improper and unsafe oil burner operation. This is because the spray angle must match the shape of the combustion chamber. A flame that is too big or too long can impinge on the back of the combustion chamber, causing improper flame, improper combustion, and even damage to the combustion chamber.

Therefore, it is crucial to refer to the manufacturer's recommendations and seek the assistance of a trained technician when adjusting the nozzle size or spray angle of your fuel oil furnace.

The nozzle spray pattern should be solid or hollow, depending on the burner

The spray pattern is chosen to fit the general shape and length of the combustion chamber. In a larger, deeper combustion chamber, a more narrow spray pattern in the 30° to 60° range is typically used. Conversely, in a shorter or smaller combustion chamber, a wider-angle spray pattern, perhaps in the 70° to 90° angle range, is used to prevent impingement of heating oil on the combustion chamber rear wall.

It is important to match the spray pattern to the air flow pattern of the oil burner. Solid spray patterns are more often used in larger or industrial oil burners, while hollow spray patterns typically result in an easier-to-set and cleaner flame in a small oil burner.

The nozzle spray angle should match the combustion chamber design

The nozzle spray angle is just one of several parameters that need to be matched to the combustion chamber design. The nozzle spray pattern (e.g. solid vs hollow cone) is also important, as it affects how the flame interacts with the air flow pattern of the burner. The nozzle size in gallons per hour (GPH) is another critical factor, as it determines the size of the flame. If the nozzle size is too large, the flame may be too big for the chamber, leading to improper combustion and potential damage to the chamber. On the other hand, if the nozzle size is too small, the burner may short cycle, resulting in reduced efficiency and increased fuel consumption.

It is important to note that changing the nozzle spray angle is a more serious error than changing the nozzle size or pattern. This is because the spray angle directly affects the shape and length of the flame, which must fit properly within the combustion chamber. Therefore, when substituting a nozzle, it is generally recommended to stay with the same angle as the original nozzle, or at least within a similar range. For example, going from a 60-degree angle to a 70- or 80-degree angle may be acceptable, but changing to a much wider or narrower angle could cause problems.

When selecting a nozzle for an oil burner, it is crucial to refer to the manufacturer's specifications. The manufacturer will typically provide a sticker or tag on the burner or the heating appliance (boiler or furnace) specifying the recommended nozzle size, pattern, and angle for that particular application. This information can also usually be found in the instruction manual or service manual for the burner or heating appliance. If this information cannot be located, it may be necessary to consult a trained service technician who can inspect the combustion chamber and recommend an appropriate nozzle configuration.

The nozzle should be properly cleaned, tuned and adjusted

To ensure your fuel oil furnace is working efficiently, it is important to keep the nozzle clean, tuned, and adjusted.

Cleaning

Over time, soot and other combustion by-products can build up on the nozzle, so it is important to clean it regularly. This can be done with a brush and a shop vacuum.

Tuning and Adjusting

A properly tuned and adjusted nozzle will ensure the furnace is running efficiently and safely. This includes setting the air-fuel ratio, stack temperature, and barometric pressure.

When replacing the nozzle, it is important to choose the correct size. A smaller nozzle may be more suitable for a smaller home, as it will reduce the furnace's output. However, a smaller nozzle may require adjustments to the air flow and fan speed to ensure the furnace runs efficiently.

It is also important to ensure that the spray pattern of the new nozzle matches the old one. If the spray pattern changes, the drawer assembly may need to be adjusted.

Finally, a combustion analyser should be used to ensure the furnace is running correctly after any adjustments are made.

The nozzle should be compatible with the oil-burning appliance

The nozzle's metering rate or firing rate in GPH (gallons per hour) is the capacity of the oil burner nozzle to deliver heating oil or the capacity of the oil burner to deliver BTUs. The metering rate is expressed in GPH and is usually 100 psi. The nozzle's spray angle and spray pattern are also stamped into the nozzle.

It is important to use the correct nozzle for your oil-burning appliance, as using the wrong nozzle can result in incomplete combustion, sooty operation, and even a puffback explosion. The manufacturer of the oil-burning appliance will usually provide a sticker or data tag that gives the acceptable firing range in GPH and the specific nozzle pattern (angle and spray type). This information can also be found in the installation and service manual for the appliance.

If you cannot find the recommended nozzle specifications for your appliance, you can calculate the right oil burner nozzle size or firing rate in GPH using the following formulas:

• Nozzle GPH = BTU INPUT / 140,000
• Nozzle GPH = BTU OUTPUT / (Heater % Efficiency) x 140,000
• Nozzle GPH = Total Sq.Ft. Hot Water x 165 / (Heater % Efficiency) x 140,000 (for hydronic radiation)
• Nozzle GPH = Total Sq.Ft. Steam x 240 / (Heater % Efficiency) x 140,000 (for steam radiation)

Frequently asked questions