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NORA Oilheat Technicians Manual

Figure 5-20: Recommended minimum inside dimensions of refractory-type combustion chambers NOTES: 1. Flame lengths are approximately as shown in column 2. Tested boilers or furnaces will often operate well with chambers shorter than the lengths shown in column 2. 2. As a general practice, any of these dimensions can be exceeded without much effect on combustion. 3. Chambers in the form of horizontal cylinders should be at least as large in diameter as the dimension in column 3. Horizontal stainless steel cylindrical chambers should be 1 to 4 inches larger in diameter than the figures in column 3 and should be used only on wet base boilers with nonretention Chapter 5 Nozzles and Chambers 5-20 Nozzles and Combustion Chambers burners. 4. Wing walls are not recommended. Corbels are not necessary, though they might be of benefit to good heat distribution in certain boiler or furnace designs, especially with non-retention burners. 1 2 3 4 5 6 Firing Rate Length Width Dimension Suggested Minimum Dia. (gph) (L) (W) (C) Height (H) Vertical Cyl. 0.50 8 7 4.0 8 8 0.65 8 7 4.5 9 8 0.75 9 8 4.5 9 9 0.85 9 8 4.5 9 9 1.00 10 9 5.0 10 10 1.10 10 9 5.0 10 10 1.25 11 10 5.0 10 11 1.35 12 10 5.0 10 11 1.50 12 11 5.5 11 12 1.65 12 11 5.5 11 13 1.75 14 11 5.5 11 13 2.00 15 12 5.5 11 14 2.25 16 12 6.0 12 15 2.50 17 13 6.0 12 16 2.75 18 14 6.0 12 18 chambers available. If the existing chamber is in reasonable condition, ceramic liners are an option. If you find yourself in a situation where the chamber must be replaced and there is no pre-cast one available for that furnace or boiler, you may have to build a chamber. If so, the following step-by-step procedure may be helpful—especially for dry base boilers. 1. Remove the old chamber. 2. Seal up any leaks in the unit base. 3. Lay down a 1" layer of powdered insulating material on the unit floor. This will reduce sound transmission and level uneven surfaces. 4. If you are building the chamber on non-combustible material, lay down a 1" floor of insulating fire brick. 5. Using insulating firebrick, build the bottom half of the chamber in a shape suitable to the burner’s fuel and air patterns.


NORA Oilheat Technicians Manual
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