1. ## Ventilating fan calculation

Dear HVAC experts,

What is the first important thing to be considered when doing calculation for ventilation fan?

Is it for fresh air, or cooling. Need to know that to know how much air you need to move.

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4. 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?

5. You answered type, but not why or how much. What is the problem you are solving?

6. Originally Posted by hien.nguyenquoc
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?
Next thing you need to figure out is the total heat gain into the room from walls and equipment.

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.

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## What electrical panels ? Do they produce heat?

Originally Posted by hien.nguyenquoc
It is for a room contained several electrical panels and it is commercial 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?

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)

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