BOILER BOOK CFC-E
STACK/BREECHING SIZE CRITERIA
40
The design of the stack and breeching must provide the required draft at each boiler flue gas
connection; proper draft is critical to burner performance.
Although constant pressure at the flue gas outlet is not required, it is necessary to size the breeching
and stack to limit flue gas pressure variation. Consideration of the draft must be given whenever
direct vent combustion is utilized and lengthy runs of breeching are employed. Please note: The
allowable pressure range for design of the stack, breeching and if used, direct vent combustion pipe,
is negative 0.25" W.C. (- 62 Pa) to positive 0.25" W.C. (+62 Pa) for proper combustion and light
offs.
Whenever two or more boilers are connected to a common breeching/stack, a draft control system
may be required to ensure proper draft.
Vent Termination
To avoid the possibility of property damage or personal injury, special attention to the location of the
vent termination must be considered.
1. Combustion gases can form a white vapor plume in the winter. The plume could obstruct a
window view if the termination is installed in close proximity to windows.
2. Prevailing winds could cause freezing of Condensate and water/ice buildup on building, plants,
or roof.
3. The bottom of the vent termination and the air intake shall be located at least 12 inches above
grade, including the normal snow line.
4. Non-insulated single-wall metal vent pipe shall not be used outside in cold climates for venting
combustion gases.
5. Through the wall vents for Category II and Category IV appliances shall not terminate over public
walkways or over an area where Condensate or vapor could create a nuisance or hazard or could
be detrimental to the operation of other equipment.
6. To prevent accidental contact by people or pets, the vent termination shall be guarded.
7. DO NOT terminate vent in window well, alcove, stairwell or other recessed area, unless approved
by local authority.
8. DO NOT terminate above any door, window, or gravity air intake as Condensate can freeze
causing ice formation.
9. Locate or guard vent to prevent Condensate from damaging exterior finishes. Use a 2' x 2' rust
resistant sheet metal backing plate against brick or masonry surfaces.
10. Multiple direct stack installations require four feet clearance between the stack caps, center to
center.
Содержание CFC-E 1000
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