| 摘要 |
The casing of a rooftop heating apparatus is formed with plenum and heat exchanger compartments separated by a partition formed with a passage for air flow from the plenum compartment to the burner in the heat exchanger compartment. Damper means is mounted in the air flow passage of the partition and is normally positioned for maximum air flow with the plenum pressurized by a constant speed blower. The intake of the blower is subject to varying wind pressures. The damper means is responsive to air pressure in the plenum to vary the areas of the air flow passage proportionate to the pressure in the plenum and accordingly, to maintain the air flow to the burner at a predetermined level, whereby the burner operation is not adversely affected by gusts of wind.
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