[Equest-users] Appendix G Baseline Systems 6 and 8 - supply air temperature controls?

[Bishop, Bill]

ASHRAE Standard 90.1, G3.1.3.12 requires cooling supply air temperature reset for Systems 5 through 8.
G3.1.3.14 requires "supply air temperature setpoint shall be constant at the design condition" for Systems 6 and 8.
How should we interpret this and model it in eQUEST (for Systems 6 and 8)?

If the "design condition" in G3.1.3.14 means "peak design flow rate", I suggest the following cooling control settings:

-             COOL-CONTROL     = WARMEST

-             COOL-MIN-RESET-T = 56                    $ (assumes 76F cooling T-stat; 56F MIN-SUPPLY-T for 20F difference per G3.1.2.8)

-             RESET-PRIORITY   = AIRFLOW-FIRST

-             COOL-MAX-RESET-T = 61                   $ (5F reset per G3.1.3.12; assumes 76F cooling T-stat)

Using a RESET-PRIORITY of "TEMP-FIRST" resets the supply air temperature before the airflow, which does not satisfy the G3.1.3.14 requirement.
Using a RESET-PRIORITY of "TEMP-FIRST" or "SIMULTANEOUS" does not satisfy the G3.1.3.12 requirement, since temperature is reset well  before minimum cooling load conditions are reached.

Does anyone have an alternative/additional suggestion or interpretation?

Thanks,
Bill

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

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