determining the supply air needed for an indusrial room

[henegg]

Hello

I am sizing a make up air unit. this is the first time I have done this.
We are only worried about heating the room.
I have calculated the following:

the air flow need for 10 air changes.

the heat loss in through the walls and roof and quantity of air needed to make up for this loss

the quantity of air need to keep the room pressurized at .05 in water.

how do I put all this info together to siz the unit?
add them all together?
do I pick the larger of the three?
Or??



thanks
Tom

 

[Xera]

Depends on what you are going to do in that room.

Storage, process, office?

 

[MintJulep]

the air flow need for 10 air changes.

10 air changes per how often? Where did this requirement come from?

the heat loss in through the walls and roof and quantity of air needed to make up for this loss

Air doesn't make up for heat loss. Air at a temperature does. Within limits you can play with the temperature.

the quantity of air need to keep the room pressurized at .05 in water.

Where did this requirement come from?

In an ideal fantasy world all of these conditions converge at a single value of air flow.

In the real world you decide which is most important, then see what that gets you for the others. Repeat until you have acceptable values for all.

 

[cdxx139]

Assuming the requirements and your calculations are all correct, you would choose the larger of the three, that way you cover all three.

A simple example is a classroom with a kitchen hood. If the ventilation requirement is 400 cfm, and the hood exhausts 1000 cfm, you need to meet the makeup air requirement of the hood, then you automatically meet (exceed) the ventilation requirement

knowledge is power

 

[ChasBean1]

What is the area of the space, what is the space used for, how many people will occupy it, and what is the rough internal heat output from equipment in the space. Answer those questions first.

The 10 ACH should be secondary, don't design around it. You might find it's met after meeting needs of the above.