Why checking the burner flame color and shape in water heaters is important? What should you do if the flame has a yellow, orange or blue glow? What are the most common problems if the gas is not burning correctly, and how to avoid it? How does the normal flame color and shape look like?
Every gas-powered and tank-type water heater uses the gas burner located in the combustion chamber to heat water, pilot light or electrode to light the fire, and a gas control valve to deliver natural gas or propane.
During the burning process, exhaust gases are vented out, either naturally (convection) or forced (electric blower). Therefore, tank-type water heaters are divided into atmospheric, power, direct, and power direct models.
Most of the models have a viewport (opening) at the bottom of the unit where you can check the condition of the gas burner, how does the flame looks like, and does it require any action or not.
If the gas burner produces a blue flame that means that everything is OK, and the air/gas mixture is in the correct ratio.
A yellow flame occurs when there is not enough air coming to the flame.
An orange or red flame happens when the dust and other debris burn together with the gas.
Note: The orange flame doesn't always indicate a problem, as it could last for a minute or two, and as the dust settles down or gets burned, the flame goes back to a blue glow. But, it is always recommended to contact an expert to check gas combustion.
Most of today's gas water heaters are equipped with the FVIR or Flammable Vapor Ignition Resistant technology and unique flame-arrestor feature, which prevents the flame and burning vapors from escaping the combustion chamber risking the open fire and potentially - explosion. Those water heaters subjected to this problem will show discoloration on the flame arrestor, requiring you to replace the unit.
Some gas water heaters are equipped with an air shutter, which allows you to adjust the air gas mixture for proper burning. Too much air will cause the burner flame to lift off the burner ports and burn with the noise. On the other side, if the flame becomes starved for air, the gas combustion becomes incomplete and will result in sooting.
The manually adjustable air shutter is usually found on the cast iron burners, while the steel burners utilize the self-adjusting air mixture.
The leading indicators of the proper gas combustion are the stable blue flame or blue flame with the yellow inner cones (see the picture).
Proper operation requires sufficient air supply and ventilation, and the venting and exhaust system must not be blocked or obstructed. Fresh air is usually delivered through the provisions on the wall (atmospheric type water heater), which must be made per codes and manufacturer's instructions.
Correctly formed burner flame on the water heater also depends on the adequate draft in the draft hood, so a regular check-up is recommended. One of the easiest ways is to use the match or candle flame or smoke, put it close to the draft hood, and if the steady flame or smoke is drawn into the opening, the proper draft is established.
If the match flame flutters or is blown out, that means products of combustion are not going through the vent system correctly but are escaping in the surrounding, contaminating the air. The changes are visible on the burner flame also, as the burner flame changes its color to yellow or orange and the stable pattern becomes unstable; it is lazy or lifts off the ports...
Note: If you find the flame unstable in an old water heater and you are unsuccessful in identifying the problem, install a new gas unit, especially if you have other gas appliances on the same line operating without problems.
Sooting is caused due to incomplete burning. Soot can be recognized as the black substance consisting mainly of carbon particles that can accumulate on the heater's elements, affecting its regular operation or even worse affect your health. Except the natural gas burners, the problem can also occur in propane heaters if the incorrect components (orifice) are used or gas regulators.
Since sooting is the sign of improper heating operation and as it can affect your health, contact your local water heater expert to help you solve the problem.
Keep in mind that an adequate supply of combustion and ventilating air must be provided without any obstructions. If there is an insufficient supply of air, the products of combustion will re-circulate, which will contaminate the surrounding air and cause health issues.
As seen from the above text, one of the first signals of improper gas combustion is the change in flame pattern, color, shape, and height.
Visual checking of the main burner, burner flame, and pilot light should be done regularly, at least once in six months, followed by cleaning the dust and debris on the gas burner and combustion chamber.
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