[Equest-users] Airflow Schedule based on Occupancy

[Bishop, Bill via Equest-users]

Hi Darryl,
First, I would use a user expression for ZONE: MIN-FLOW-RATIO for any zones that you want to control to 6 ACH minimum. Then I would create and apply a ZONE: MIN-FLOW-SCH with values of 1.0 during occupied hours and -999 for unoccupied hours. The expression below for MIN-FLOW-RATIO should give you 6 ACH . It will give you an error if a value is entered for ASSIGNED-FLOW that is less than 6 ACH.
Regards,
~Bill

/* This expression for ZONE:MIN-FLOW-RATIO calculates and enters
   a value based on a desired minimum ACH. */

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(#L("AIR-CHANGES/HR")) == 0
                .AND. #L("AIR-CHANGES/HR") = 6) then 1  $ 6 ACH
         else if (#RV(#L("ASSIGNED-FLOW")) == 0) then
          6*#LR("SPACE","HEIGHT")*#LR("SPACE","AREA")/60/#L("ASSIGNED-FLOW")
          else no_default endif
              endif
    endswitch
   endif

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] On Behalf Of Darryl Kasun via Equest-users
Sent: Tuesday, October 25, 2016 1:54 PM
To: equest <equest-users at lists.onebuilding.org>
Subject: [Equest-users] Airflow Schedule based on Occupancy

Hi everyone,

I have a zone that is served by a VAV system.  The controls for the zone state that when the zone is occupied, the VAV box should be fully opened and when unoccupied, the zone supply air be reduced to 6 ACH.  There are multiple zones controlled in this manner.

To model this I am thinking of creating a min airflow schedule that matches occupancy schedule.  The minimum hourly fraction within the min airflow schedule would be equivalent to the airflow fraction of 6 ACH.

In other words, if there are hourly fractions in the min airflow schedule (which is a copy of the occupancy schedule) that are below the equivalent fraction of 6 ACH, those hours would be changed to the 6 ACH fraction.

Hopefully that makes sense to you.

This method seems fine to me but a bit tedious as it will require developing multiple min airflow schedules.

Any thoughts?


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