Boiler and Burner Combustion Air Supply Requirements and Maintenance

Boiler and Burner Combustion Air Supply Requirements and Maintenance

Whether operating inside or outside of the building, you should be aware of the necessary air supply for boiler and burner combustion. The amount of air required varies based on the size of the boiler or burner and the operating conditions. For example, a burner operating inside a tightly sealed building should receive at least one square inch of free air per 5000 Btu/hr or 28 square inches per GPH of #2 fuel oil.

Ventilation

The amount of ventilation required in a boiler room varies depending on the style and age of the building. For example, if the boiler room is located in a crawlspace, the combustion air supply should come through a wall with an open area of at least one square inch for each 5,000 Btu/h of combustion air. This air supply must be sufficient for the boiler to operate properly. If the room is not vented, then fresh air should be brought into the room through an exterior wall. Be sure to protect the ducts from leaves, plastic bags, and bird nests. Also, make sure that the ducting is insulated, and that the pressure drop is not more than 0.05″ w.c.

The International Fuel Gas Code and the National Fire Protection Association (NFPA) recommend that boiler rooms have at least two openings. This allows for natural ventilation inside the room and minimizes the risk of the combustion air opening being blocked by leaves, wood, or cardboard. Another requirement for combustion air is that each burner must have at least two open spaces that are one inch apart.

Condensate drain

If your boiler or burner produces condensate, you need to drain the liquid away from the unit. You can do this with a condensate drain or floor drain. In either case, you need to make sure that the pipe used to drain the condensate is of the correct size. Generally speaking, the condensate drain pipe must be at least 3/4 inch in internal diameter. Ideally, you should use schedule 40 metal pipe.

A malfunctioning condensate drain can lead to serious problems. It can cause a no-heat call or flood the combustion chamber, preventing flue gas flow and blocking the flame sensor. It can also cause your boiler/burner to lock up.

To maintain the performance of your boiler/burner, you need to properly drain the condensate. The condensate from a condensing boiler can be acidic, so the pipe material must be corrosion-resistant.

Steam “blow-down” lines

Combustion air flow is one of the most critical elements for proper operation and maintenance of a boiler/burner. Proper air supply and filtration are essential for optimal combustion, and a boiler/burner can only perform properly if all of the systems are in proper working condition. This includes the boiler room air supply, flue gas system exhaust, and power distribution grid. The boiler room air supply is the starting point of the combustion process, and any deficiencies in the air supply will cause the boiler/burner to malfunction.

The combustion air used in a boiler/burner should be free of corrosive, explosive, or flammable vapors. It is important to use a corrosion guide to determine the corrosive nature of the gasses that are used. The air should be warm enough for combustion but not too cold. Often, side wall venting is acceptable, although it must be mechanical convection or gravity-driven.

Proper boiler/burner set-up and maintenance can significantly reduce VOC emissions. Proper air/fuel ratio, proper atomizing air pressure, and proper combustion air supply are vital for controlling VOCs. Without the proper set-up, combustion can’t occur properly, resulting in high VOC emissions.

 

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