COWB3 OIL-FIRED HOT WATER BOILER WATER HEATING
2020-4-27 · For applications with outside air, each opening should have a minimum free area of 1 in.2 (645 mm2) per 4000 Btu per hour (1.17 kW per hour) for vertical ducts and 2000 Btu per hour (0.59 kW per hour) for horizontal ducts to the outside.
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