AHU Supply Air Temperature

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Without seeing your actual sequence of operation I can't be sure of the intent, but here are my two cents.

I'd say that the SAT being based off of OAT is irrelevant or at least should be, and you can talk to your MEP about it and propose another one.

Given the portion about looking at deviation of space temperature compared to setpoint, that makes me think there will be a BMS/EMS polling information from the spaces throughout the building. In this case, you should reset your discharge temperature so that the warmest zone can be adequately cooled, while minimizing the reheating done by your radiant panels in other zones.

In EnergyPlus, you should use a SetpointManager:Warmest to implement this strategy. The control temperature will be temperature, the strategy "MaximumTemperature", and you need to put in the bounds for discharge temp. The Minimum setpoint temperature is your design temperature for summer/cooling (typically 55F) and the maximum temperature should be the design temperature for winter/heating, whatever that is in your case (80F for example, or 70F maybe if you're sending neutral air and letting the radiant panels do the rest).