You need to ensure your water heater has proper combustion air to function safely and efficiently. This is because combustion air is required to support the burning of fuel, typically natural gas or propane, that heats your water.
The International Fuel Gas Code (IFGC) requires a minimum of 50 cubic feet per minute (cfm) of combustion air for water heaters. This can be achieved through various means, including installing a combustion air intake vent or ensuring the water heater is installed in a well-ventilated area.
Water heaters installed in certain areas, such as garages or enclosed spaces, require additional combustion air to prevent backdrafting and ensure safe operation.
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What Is Combustion Air?
Combustion air is essential for safe and efficient operation of your water heater. It's the air that's supplied to the appliance to be used in the combustion of fuels and the process of venting combustion gases.
According to the Housing Industry Research Center, combustion air has two definitions: it's the air that's supplied to the water heater, and it's also the duct work installed to bring fresh, outside air to the appliance. This duct work is crucial for proper ventilation and combustion.
Fresh outside air is usually brought in through separate supplies, one high for ventilation and one low for combustion. The type of ventilation system you have depends on the year of construction and the style of your dwelling, with options including crawlspace vents, exterior wall vents, or roof vents.
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What Is It?
Combustion air is the air that is drawn into a combustion chamber or furnace to support the burning of fuels such as natural gas, oil, or wood.
This air is essential for the combustion process to occur, providing the oxygen needed to sustain the chemical reaction that produces heat and energy.
Combustion air is typically drawn into the combustion chamber through vents or openings, and it can be either outside air or recirculated air from the building.
The amount of combustion air required can vary depending on the type and size of the fuel being burned, as well as the efficiency of the combustion system.
In a typical residential furnace, the combustion air is usually provided by a separate vent or opening, which is designed to draw in a sufficient amount of air to support the combustion process.
This separate vent or opening is often located near the furnace or water heater, and it's usually designed to be easily accessible for maintenance and cleaning.
Combustion air can also be provided by the building itself, through openings such as windows, doors, or vents that are designed to allow air to enter the space.
Why Is It Important?
Having a clear understanding of combustion air is crucial for safe and efficient heating.
Inadequate combustion air can lead to dangerous problems, such as increased indoor carbon monoxide levels.
Combustion air is essential for the proper functioning of fossil fuel burning appliances.
A recent warning from XCEL Energy highlights the importance of maintaining proper ventilation to prevent carbon monoxide buildup.
All fossil fuel heating systems, including forced air furnaces and water heaters, require ample air intake and draft.
The Housing Industry Research Center defines combustion air as air supplied to combustion appliances for fuel combustion and venting combustion gases.
Inadequate combustion air can be caused by obstructed vents, such as exterior vents blocked by snow buildup or interior vents blocked by household items.
Proper combustion air supply is critical for safe and efficient operation of gas appliances, and it's essential to locate and inspect vents to ensure they are freely open and unobstructed.
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Water Heater Requirements
A space is considered confined if the total cubic feet needed to support combustion and ventilation is larger than the total cubic feet available.
To determine if a space is confined, you need to calculate the total cubic feet of space needed to support combustion and ventilation by multiplying the BTU rating of your gas-fired equipment by 50.
For example, a 100,000 BTU gas-fired boiler and a 50,000 BTU gas-fired water heater require a total of 7000 cubic feet of space to support combustion and ventilation.
If the total cubic feet of space needed is greater than the total cubic feet available, combustion air must be acquired from another space.
To size the opening for outside air, you need to have 1 square inch of free air for every 3000 BTU's fired in that space.
For a boiler room with a 50,000 BTU gas-fired water heater and a 100,000 BTU gas-fired boiler, the free air space must be 50 square inches or a 10 x 5 inch opening to the outside of the building.
Some grills or louvers may have a specified free air space, but if not, you can use the following sizing percentages: Wood/Plastic = 25% free area; Metal = 75% free area.
A 10 x 10 inch unmarked wood or plastic louver has a total of 100 square inches, but only 25 square inches of free air space.
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Resource Considerations
When choosing a water heater, consider the amount of space you have available for the unit and its combustion air requirements. The combustion air requirements for a water heater can be a significant factor in determining the overall size and placement of the unit.
Typically, a water heater requires a minimum of 50 cubic feet of free space around it for proper combustion air flow. This space is crucial for the safe and efficient operation of the water heater.
The type of fuel used by the water heater also plays a role in determining its combustion air requirements. For example, a gas water heater requires a different amount of combustion air than an electric water heater.
A gas water heater typically requires a minimum of 25 cubic feet of free space around it for proper combustion air flow, while an electric water heater requires no combustion air at all.
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Frequently Asked Questions
What happens if you don't have enough combustion air?
Insufficient combustion air can lead to the buildup of deadly carbon monoxide (CO) in your home, posing a serious health risk
Do you need to purge air from a hot water heater?
Yes, purging air from a hot water heater is necessary to maintain its performance and prevent costly issues. Regular purging can also lower energy bills and extend the tank's lifespan.
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