Outside Air Supply

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Hi all,

I am trying to set up a model to which uses minimum ASHRAE 62.1 ventilation
rates and I'm having a bit of trouble. My understanding is that in the zone
setup the outdoor air can be setup to use 4 different specification methods,
but equest will only use whichever is greatest (ie, 5cfm/person or .06
cfm/sqft) but not combine them. It therefore seems like the best method for
this is to use 62.1 to calculate cfm/zone and just enter that number.

I then go to my system screen for OA, where I can specify the OA ratio,
control method, etc. If I set the ratio to be 1, and the sizing method to
be Sum of Zone OA , then when I go to the SV-A report shouldn't my numbers
there match exactly what I have entered for all my design values? I set up
a very simple zone that had 100 cfm design flow, 50 cfm min OA, and 50 cfm
exhaust, and then when I run a simulation and open the SV-A report it lists
my design cfm as 103, OA as 52, and exhaust as 53. I don't understand why
these design values are slightly higher, anyone have any thoughts?

Michael Shields, EIT
Facility Strategies Group, LLC

1012 Market Street, Suite 307

Fort Mill, SC 29708

Phone: 803-493-4507

Fax: 803-548-2511
Email: mshields at fstrategies.com

M. Shields's picture
Joined: 2011-09-30
Reputation: 0

Go into your Project and Site tab and set your altitude to 0. For an
explanation of this search the archives.

cmg750's picture
Joined: 2010-10-05
Reputation: 0

Thanks Carol, that was indeed what was causing the difference. It looks
like I missed a fairly lengthy discussion that was previously held on the
list when trying to figure it out.


M. Shields's picture
Joined: 2011-09-30
Reputation: 0