[Equest-users] Min Allowable Supply Air Flow

[Bishop, Bill via Equest-users]

Darryl,
You can enter the expression below as a custom default expression for zone MIN-FLOW/AREA based on the desired minimum ACH.
It will calculate the minimum cfm/ft2 based on 6 ACH, and use the smaller of that value or the equivalent value for zone AIR-CHANGES/HR if it is entered for that zone.
~Bill

if (#RV(#L("AIR-CHANGES/HR")) == 0 .AND. #L("AIR-CHANGES/HR") <= 6)
then #L("AIR-CHANGES/HR")*#LR("SPACE","HEIGHT")/60
else 6*#LR("SPACE","HEIGHT")/60 endif


From: Darryl Kasun [mailto:darryl.kasun at gmail.com]
Sent: Thursday, August 25, 2016 1:29 PM
To: Bishop, Bill <bbishop at pathfinder-ea.com>
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Min Allowable Supply Air Flow

Hi Bill,

eQuest coding is over my head at this stage but I appreciate your feedback.  In my case, I do not know the design ACH but I do know design flows (ZONE:ASSIGNED-FLOW) and want a min 6 ACH.

How would that change the expression you provided??  No worries if it's a bit of a pain, I can always do some manual calcs for each zone.

Thanks
Darryl

On Thu, Aug 25, 2016 at 6:03 AM, Bishop, Bill <bbishop at pathfinder-ea.com<mailto:bbishop at pathfinder-ea.com>> wrote:
Darryl,
There is no zone keyword for minimum ACH. But you can enter the zone design ACH (ZONE:AIR-CHANGES/HR) and set the minimum air changes as a percentage of this using ZONE:MIN-FLOW-RATIO. You can write a keyword expression that enters and calculates this based on other zone inputs if you wanted to. For example, the expression below modifies the default DOE-2 expression for MIN-FLOW-RATIO, adding a calculation step based on the zone input for AIR-CHANGES/HR. The sample calculation assumes you want a minimum ACH of 3, and calculates the MIN-FLOW-RATIO for any zones for which you enter a design ACH rate of 3 or more.
if (#P("MIN-CFM-RATIO") == unused)
    then unused
    else switch #SV(#P("TYPE"))
    case  2 : unused
    case 17 : unused
    case 19 : unused
    case 26 : unused
    case 27 : unused
    case 28 : unused
    case 29 : unused
    default : if (#RV(#P("MIN-CFM-RATIO")) == 0)
              then #P("MIN-CFM-RATIO")
              else if (#RV(#L("AIR-CHANGES/HR")) == 0
                .AND. #L("AIR-CHANGES/HR") >= 3) then
                3/#L("AIR-CHANGES/HR") else no_default endif
              endif
    endswitch
   endif

Regards,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of Darryl Kasun via Equest-users
Sent: Wednesday, August 24, 2016 5:59 PM
To: equest <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Subject: [Equest-users] Min Allowable Supply Air Flow

Hello again eQUESTers,

For some zones, I want to set the min. allowable zone air supply flow rate to a certain ACH.  There is a zonal input for min. design air changes/hr but I think eQUEST will go below this flow if possible.  Sure I can calculate the minimum flow as cfm.ft2 or ratio but would like to not do this work if possible!

Is there a straight-up min. allowable ACH input for eQUEST?

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