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NORA Oilheat Technicians Manual

the appliance, the manufacturer’s instructions must be followed. Installing flue pipe Be sure to check the condition of the flue pipe during each service call. If it looks questionable—replace it. The stack temperatures on new high efficiency units are much lower and are more likely to cause condensation and rusting of the flue pipe. This is extremely important because combustion gases can enter the building if the flue pipe is porous or disconnected. The flue pipe must be at least 18 inches 6-10 Draft and Venting from a combustible wall or ceiling as a fire prevention measure. It should never be smaller than the flue pipe collar at the breech of the boiler or furnace. The flue pipe should be as short as possible and should not exceed 10 feet of horizontal run unless a draft fan is used. It should have a minimum of ¼" per foot pitch from the appliance up to the chimney and be run with minimum number of elbows. Use 45-degree elbows instead of 90’s when possible. The flue pipe should be firmly joined with sheet metal screws and supported with straps or wire. It should be tightly fitted to the breeching and installed into a clay or metal thimble that is securely cemented into the chimney. Be sure the thimble and pipe do not protrude beyond the inside wall of the chimney tile. No sort of dampers, except for the barometric damper (draft regulator) should be installed in the flue pipe or breeching. They are not needed and could cause problems if they close accidentally. Chimney and draft problems Insufficient draft can occur with too many appliances connected to a chimney. Whenever connecting two or more fuel burning appliances to a single chimney, verify that there is sufficient draft for safe operation of all units. Insufficient draft also occurs when obstructions such as soot, loose bricks, birds’ nests or other foreign objects build up in the chimney and restrict flow. See Figure 6-7 for common chimney troubles and their corrections. Lack of air in the furnace room Insulation, tight windows and doors, and tight construction can prevent outside air from entering the building. As a result, the building cannot ‘breathe.’ Oilburner Chapter 6 Draft and Venting


NORA Oilheat Technicians Manual
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