What is combustion air? It is the air necessary for a gas appliance such as a water heater to function properly. Not to get too basic here, but gas appliances require a certain amount of air to be used for combustion, much the same way that the fire in your fireplace needs air to get started and to keep burning. If there’s not enough air, the flame goes out and it’s the same with the burner and pilot light on a typical gas appliance. Most people just assume if there is any amount of air, that should be enough, but that is not true. If you’re having troubles with your pilot light on your water heater and it keeps going out or if the burner assembly is having trouble staying lit or burning properly, it could be due to a lack of combustion air.
So how do you determine if there is enough combustion air? First, you have to establish that the room is large enough to provide the necessary amount of combustion air. Basically, there should be 50 cubic feet of air per 1,000 BTUs required by the appliance. Let’s just use a water heater as our typical appliance since we are Water Heaters Only, Inc. If a standard residential water heater requires 40,000 BTUs per hour, then once you start doing the math, you realize that you need a pretty good-sized room to provide enough air for your appliance. This is why gas appliances such as water heaters are often located in the garage. If the room your water heater or furnace is in isn’t big enough to provide enough combustion air, then it is considered a confined space and air will have to be made available through other means.
Is your water heater located in an outside or inside closet? If so, then air will have to be brought in from the outside, usually through the use of vents or ventilation openings on the door of the closet or the wall. If this is the case, then there will have to be two vents. A top vent located within 12 inches of the ceiling and a bottom vent located within 12 inches of the floor. These vents also need to be sized properly. The general rule is that the vents need to have one square inch for every 1,000 BTUs required. This is for vents that are providing air from a larger room on the other side of the closet where the water heater is located. If your water heater is in an outside closet, then the ratio is 1 square inch for every 4,000 BTUs required. This math changes depending on whether there are grills or screens covering these vents. Don’t worry about getting all the math correct, just have a licensed plumber or contractor come out and let them do the work for you.
However, it should be noted that even if there is enough combustion air being provided from the room itself, there could still be issues if the water heater is surrounded by clutter. Even if it is located in the garage, if the water heater can’t pull in enough air because it is surrounded by lawn chairs and camping equipment or whatever, then there could still be an issue. It is best if the water heater has a two-foot area cleared of any items or trash. This will ensure that the right amount of air will be available for your water heater to operate properly.
Similar problems can be found with commercial water heaters that are often located in a laundry room. Lint and other debris can be sucked into the burner causing the water heater to malfunction. It is best to keep the surrounding area as clean as possible whether it is a residential or commercial water heater. It’s also a good idea to have the water heater inspected on a regular basis, especially if it is a commercial water heater in the laundry room.
So now you should have a basic understanding of combustion air and how it relates to gas appliances such as water heaters. The rules are pretty basic: Make sure there is enough air available for the appliance and that means making sure the room it is located in is big enough or there is enough air being provided from an outside source. It also means making sure the area around the water heater is clear of debris and there isn’t a lot of dust, lint and other particulate matter floating around that could give the burner problems. Finally, have your water heater inspected regularly to ensure it is getting air to allow it to operate properly and efficiently.