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Thread: Ventilating fan calculation
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05-24-2011, 12:45 AM #1
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Ventilating fan calculation
Dear HVAC experts,
What is the first important thing to be considered when doing calculation for ventilation fan?
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05-24-2011, 05:22 AM #2
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Knowing why your ventilating.
Is it for fresh air, or cooling. Need to know that to know how much air you need to move.
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05-24-2011, 05:33 AM #3
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TYPE - Residential, Commerical, Institutional
# of people - House, Movie Theater, ChurchDesigner Dan
It's Not Rocket Science, But It is SCIENCE with "Some Art".
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities
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05-30-2011, 12:28 PM #4
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It is for a room contained several electrical panels and it is coomercial ventilating.
I have not yet known how much air I need to move. But what is the next step to think of? Measuring the room temperature?
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05-30-2011, 01:29 PM #5
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You answered type, but not why or how much. What is the problem you are solving?
Which makes more sense to you?
CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%
DO THE NUMBERS! Step on a HOMESCALE.
What is comfort? Well, it AIN'T just TEMPERATURE!
Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.
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05-30-2011, 01:51 PM #6
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Next thing you need to figure out is the total heat gain into the room from walls and equipment.
Originally Posted by hien.nguyenquoc
After that you need to know what temperature the room needs to be. Then, know what temperature you have available, presuming you are relying on exhaust air from an adjacent space. With the above, you can do thecalculate the required CFM.If a nation expects to be ignorant and free, in a state of civilization, it expects what will never be. (Thomas Jefferson 1816)
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05-30-2011, 10:24 PM #7
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What electrical panels ? Do they produce heat?
Originally Posted by hien.nguyenquoc
K.I.S.S.
1
How much heat (Q - BTU/Hr) do the panels produce?
2
What is the source of "cool air" that can be used?
What is the temperature of the "cool air" (Tc) ?
3
What is the upper temperature limit (Th) of any components in the room that is being ventilated?
Q = dT * CFM * constant
Constant might be close to 1.0 or up to ~ 1.07
CFM = Q / dT
___ = Q / ( Th -Tc)Designer Dan
It's Not Rocket Science, But It is SCIENCE with "Some Art".
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities
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