[Equest-users] USER EXPRESSION

[Bishop, Bill]

Hi Tejas,
I believe that eQUEST/DOE-2 always gives priority to outside air flow, so that hourly outdoor air requirements are always satisfied, consistent with the zone and/or system OA cfm values and control method. Therefore, the “minimum outdoor air flow rate” requirement in ASHRAE 90.1-G3.1.3.13 is automatically met.
So you enter 0.30 for the SYSTEM:MIN-FLOW-RATIO and you meet the 30% minimum flow requirement. (You can also enter minimum flow at the zones using ZONE:MIN-FLOW-RATIO, but the default expression copies the system-level value if it is entered.)
HOWEVER, if you still wanted an expression that sets the MIN-FLOW-RATIO to the greater of 30% or SYSTEM:MIN-OUTSIDE-AIR, you could use this expression for SYSTEM:MIN-FLOW-RATIO:
if (#RV(#L("MIN-OUTSIDE-AIR")) == 0)
              then MAX(#L("MIN-OUTSIDE-AIR"),0.30)
              else 0.30
              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] On Behalf Of equest user via Equest-users
Sent: Thursday, February 15, 2018 7:17 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] USER EXPRESSION

Hi all Modelers,

This question is for all those 'user expressions' prodigies.

Can anyone guide me on how can user expression be used for MIN-FLOW RATIO in Air side sytem as ASHRAE states to keep MIN-FLOW RATIO as 0.30 or equal to Design outdoor air value whichever is greater.

I am in need of a user expression which i should be able to put in MIN- FLOW RATIO Keyword such that it
1) takes the Value as '0.30' when outdoor design ratio is less than 0.30 and
2) takes the Value same as design outdoor ratio when design ratio value is greater than 0.30

Thanks and regards,
Tejas
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