Air Requirements
Important: Air for combustion and ventilation must not come from a corrosive atmosphere. Any failure due to cor- rosive elements in the atmosphere is excluded from war- ranty coverage.
Installations in or for certain places including, but not limited to, those listed below will require outdoor air for combustion due to chemical exposure:
Beauty shops
Photo processing labs Buildings with indoor pools
Water heaters installed in laundry, hobby or craft rooms Water heaters installed near chemical storage areas
In such circumstances, outdoor combustion air may reduce, but will not eliminate, the presence of corrosive chemicals in the air. Combustion air must be free of
The area in which the heater is located is classified as either “an unconfined space” or “a confined space”.
An unconfined space is defined as a space having a vol- ume not less than 50 cubic feet per 1000 BTU/hour (4.8 cubic metres per kilowatt) of combined input rating of all appliances using the space. Adjacent open rooms may be included as part of the unconfined space, provided there are no closeable doors between these rooms. An example of this is an open basement.
A confined space is one smaller than described above. For buildings using tight construction (newer and renovated structures), the air supply shall be introduced from the out- doors, regardless of whether the space is confined or unconfined.
Confined Space Air Requirements for Canadian Installations
Refer to Figure 5 (a), or (b), and Table 1 for proper sizing and location of combustion air ducts and openings. CHECK
LOCAL CODES.
(a). Two permanent openings shall be provided connecting the confined space (e.g., closet, small room) with the unconfined space. Each opening shall have a free area of one square inch per 1,000 BTU/hour input (22 cm²/kW) of all appliances in the confined space. The top opening shall be located as close to the ceiling as prac- tical but never lower than the top of the heater. (see Figure 5 (a)). The bottom opening shall be located nei- ther more than 450mm (18 in.), nor less than 150mm (6 in.), above floor level.
(b). When using a single air supply, the duct shall terminate within 300mm (12 in.) above and within 600mm (24 in.) horizontally of the burner level of the appliance having the largest input. For example: GSW’s water heaters’ burners are 150mm (6 in.) from the floor, plus 300mm
(a)
PERMANENT
OPENINGS
CONFINED
SPACE
UNCONFINED SPACE
EQUIPMENT LOCATED IN CONFINED SPACES;
ALL AIR FROM INSIDE THE BUILDING.
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| 300mm |
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(b) | CONFINED | |||
| (12 in.) |
| SPACE | |
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GRADE
COMBINATION
COMBUSTION/
VENTILATION
AIR DUCT
600mm (24 in.)
450mm (18 in.)
BASEMENT INSTALLATION, EQUIPMENT LOCATED IN CONFINED SPACES; ALL AIR FROM OUTDOORS
Figure 5 Combustion Air Supply Openings And Ducts (Can.)
Combined Input |
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Required | Duct Size Diameter | |||||||||
of All Appliances | ||||||||||
in Confined | Free Area | A** |
| B*** |
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Space* |
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BTU / h | (kW / hr) | cm2 | in.2 | mm |
| in. | mm |
| in. | |
25,000 | 8 | 45 | 7 | 76 |
| 3 | 100 |
| 4 | |
50,000 | 15 | 45 | 7 | 76 |
| 3 | 100 |
| 4 | |
75,000 | 23 | 70 | 11 | 100 |
| 4 | 125 |
| 5 | |
100,000 | 30 | 90 | 14 | 100 |
| 4 | 125 |
| 5 | |
125,000 | 37 | 120 | 18 | 125 |
| 5 | 150 |
| 6 | |
150,000 | 45 | 140 | 22 | 125 |
| 5 | 150 |
| 6 | |
*All appliances refers to, and includes, those appliances using the same air source (e.g. water heater, furnace, boiler, clothes dryer etc.).
**Maximum allowable length of ductwork listed in column A is 6.1 equivalent metres (20 ft.).
***Maximum allowable length of ductwork listed in column B is 15.2 equivalent metres (50 ft.)
Table 1 Air Supply Sizing (Can.)
(12 in.) equals 450mm (18 in.) as shown in Figure 5 (b). All exterior vent openings are to be at least 300mm (12 in.) above the ground and clear of snow levels.
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