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NORA Oilheat Technicians Manual

When pumping ten full strokes of the smoke tester pump, do not pump too fast. Hold the handle at its most extended position a second or two between strokes. If 7-18 Combustion you take more than one sample from a burner, use the same uniform method of pumping each sample. If you fail to follow this method, you could get two different smoke numbers, even though you have made no adjustments to the burner. Chapter 7 Combustion standard graduated smoke scale, Figure 7- 18. This scale has ten shaded spots with an equal difference between successive spots. Spot Number 0 is white, and represents smoke-free combustion. Spot Number 9 (darkest) represents the maximum smoke that typically will be produced. An oily or yellow smoke spot on the filter paper is a sign of unburned fuel, indicating very poor combustion (and likely high emissions of carbon monoxide and unburned hydrocarbons). If too much excess combustion air is supplied, the combustion process will be chilled so much that some of the fuel cannot burn. The flame is actually being blown out. Further evidence is liquid fuel in the heat exchanger, white smoke (fuel vapor) and strong odors outside the home. To adjust for a zero smoke, first adjust the burner for a trace smoke then open the air gate just a bit farther to go to zero smoke. By initially adjusting to a zero smoke you will be introducing an unknown amount of excess air which can lead to: lower CO2, cooler flame temperatures, higher stack temperatures, and possible elevated carbon monoxide production. Remember that excess air cools the combustion products and increases their volume so that it is difficult for the heat exchanger to absorb the heat before it escapes to the breeching and up the chimney. Most new burners are designed to operate at zero smoke. Common causes of smoke and soot: Poor fuel atomization: small fuel droplets vaporize quicker than large ones. Large droplets are caused by: • Damaged or worn nozzles • Low fuel pump pressure • Cold oil Inadequate combustion air is caused by: • The burner air control is not open far enough • Poor chimney draft • Build up of soot and scale in the heat exchanger • Accumulation of lint, hair, sawdust, and dirt on the air shutter and the burner fan • Restrictions of the air flow to the room the burner is in, and the operation of exhaust fans that de-pressurize the building Effects of insufficient combustion air For the proper operation and venting of gas or oilheating appliances, sufficient


NORA Oilheat Technicians Manual
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