Gas & Fuel第 61 / 110 题
Combustion air is taken from outdoors using two openings, one high and one low. The rule is 1 square inch of free area per 4,000 BTU/hr for each opening when using direct outdoor openings. For a 200,000 BTU/hr appliance load, what is the minimum free area of each opening?
a.50 in^2
b.25 in^2
c.40 in^2
d.100 in^2
解析
Each opening = load / 4,000 = 200,000 / 4,000 = 50 in^2 of free area. When two vertical (direct outdoor) openings are used, each is sized at 1 square inch per 4,000 BTU/hr, one within 12 in of the top and one within 12 in of the bottom. Louvers reduce free area, so gross opening size must be increased to compensate.
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