What does the Building Code say?
National Standard of Canada - CAN/CSA-B149.1-10.
Natural gas and propane installation code
(The following sections are taken from the code regarding combustion air supply to: a) Gas Burning Appliances; b) Oil Burning Appliances.)
a) Gas Burning Appliances
8.1 General ...
8.1.3 Interference with the air supply for an appliance shall be prohibited.
8.2.3 An outdoor air supply shall not be required for a single water heater with an input of 50 000 Buth (15 kW) or less within an enclosure or structure where there are no other appliances that require an air supply.
8.3 Air-supply openings and ducts
8.3.1 (d) (The duct shall) terminate within 1 ft (300 mm) above, and within 2 ft (600 mm) horizontally from, the burner level of the appliance having the largest input.
8.5 Air-supply dampers, louvres, and grilles
8.5.2 Apertures in a fixed louvre, grille, or screen shall have no dimension smaller than 0.25 in (6mm).
8.5.3 Neither a manually operated damper nor manually adjustable louvres shall be used.
8.5.4 An automatically operated damper or automatically adjustable louver shall be interlocked so that the main burner cannot operate, unless either the damper or louver is in the fully open position.
8.5.5 An automatic combustion air damper installed in the air supply within a dwelling unit shall be certified.
b) Oil Burning Appliances: CAN/CSA-B139-09
When a damper is provided in any opening intended to admit combustion air into the room within which the appliance is installed, the damper shall be interlocked to prevent any burner from starting before the damper is fully open.
*Model National Energy Code of Canada for Houses - 5.2.3. Air Intake and Outlet Dampers
126.96.36.199. Required Dampers
1) Except as provided in Sentence (3) and (4), every duct or opening intended to discharge air to the outdoors shall be equipped with a motorized damper or gravity or spring-operated backdraft damper.
2) Except as provided in Sentence (3) and (4) and except in regions that have fewer than 35 0 degree-days (C) as listed in Appendix C of the National Building Code of Canada, every outside air intake duct or air intake opening shall be equipped with a motorized damper.
3) Where dampers are not permitted by other regulations, air intakes and outlets need not comply with Sentences (1) and (2).
4) Air intakes and outlets serving systems required to operate continuously need not comply with Sentence (1) and (2).
*Model National Energy Code of Canada For Houses 1997 - Part 188.8.131.52 Reprinted with permission From National Research Council, Canada.
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