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PPORTUNITY |
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Welcome to PPORTUNITY, a monthly newsletter provided by Jacco & Associates. Jacco’s focus on engineering and design concepts will improve your HVAC system while significantly reducing design time, making you more productive for your clients. |
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61 Milford Dr. Hudson, OH 44236 Phone:(330) 463-0100 Fax:(330) 463-0101 |
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Existing conventional stacks are of constant geometry. The stack size is selected to maintain approximately 4,000fpm at the discharge in order to diffuse the exhaust air into the atmosphere. The stack is designed for this velocity at full exhaust cfm. At times the stack may not have to exhaust as much cfm as the design intended. This could be because a lab or kitchen is not in full use and all of the fume hoods are not in operation. Since the discharge area of the stack remains the same, the velocity of the air will decrease as the need for exhaust cfm decreases. In typical systems outside air is introduced into the stack to maintain a constant discharge velocity. This is a very inefficient process. You are introducing unnecessary air in order to maintain a specific discharge velocity. Why not vary the airflow while maintaining the velocity required and pocket the energy savings? The M&I stack design integrates a venturi shaped discharge section with a cone mechanism operating in the center that varies the net opening area of the stack to maintain a constant velocity at all exhaust airflow rates. The cone can be activated using a pneumatic or electric operator and a flow sensor located at the stack discharge to maintain constant velocity at all airflow rates. A silencer is also incorporated into the stack which is aerodynamically designed, is suitable for outdoor installation, and has minimal pressure drop. All of these items are factory installed and no external controls are required. |
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Stack Exhaust Fans |
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Question: To provide 70º air at 50% RH in a reheat system, what is the required coil discharge temperature (DB/WB)? Answer: 50/50. Congratulation to Brian Rice for winning a Ping Putter! |
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Be sure to mark your calendars for Jacco’s Hospital and Healthcare Seminar on October 20th! Details to follow. |
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Vaneaxial Fan |
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Pneumatic Actuator |
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8” Roofcurb |
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Maximum CFM Position |
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Minimum CFM Position |
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Exhaust Air |