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View Full Version : Infiltration thru roll up door

Draper1
07-15-2008, 03:48 PM
Does anyone have a good method of estimating the infiltration thru a loading dock roll up door?

Paulinator
07-15-2008, 05:54 PM
I've used 0.5 ACH to account for infiltration in the case of overhead doors.

I've also seen a more complicated method where you assume an air velocity (500fpm is reasonable). With that you get your total volume going through the door in CFM.

You assume how many minutes that door is opened for.
You calculate the amount of energy it takes to heat up that volume of air. You divide by the time your allowing it to heat up the air and you get the required BTU/HR value

If you need further clarification, let me know.

jogas
07-15-2008, 07:15 PM
I've used 0.5 ACH to account for infiltration in the case of overhead doors.

I've also seen a more complicated method where you assume an air velocity (500fpm is reasonable). With that you get your total volume going through the door in CFM.

You assume how many minutes that door is opened for.
You calculate the amount of energy it takes to heat up that volume of air. You divide by the time your allowing it to heat up the air and you get the required BTU/HR value

If you need further clarification, let me know.

Shouldn't building static pressure and building height (stack effect) be a major consideration when calculating infiltration?
Believe it or not, I recently encountered a large site that was under 0.12"w.c. positive! The doors were being held open.
I've also encountered up to -0.06"W.C. buildings.
jogas

Draper1
07-15-2008, 07:21 PM
I also found a good answer in the Carrier "Handbook of Air Conditioning System Design" on page 1-94, table 43c: It lists the values of infiltration to use for a shipping room door per square foot for both normal and infrequent use. 4 CFM per square foot area for infrequent and 9 for average use. There are also other variables which are covered in footnotes.

Paulinator
07-15-2008, 09:51 PM
I wish I had a copy of carrier's design handbooks. My company wouldnt buy them for me.....lol *but thats a whole other subject*. Thanks for your insight, I have been learning quite a bit from this site as I am just a junior professional.

dandyme
07-16-2008, 06:23 AM
see if this is any help

www.ashrae.org/freeaedg.

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