Question-and-Answer Resource for the Building Energy Modeling Community
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Hello Me from the past,
Since I noticed multiple questions from the past about using hydronic economizer with air cooled plant equipment with no clear answers, I thought I would write about my approach (That seems to work) to see if someone else has any further suggestions.
The HeatExchanger:FluidToFluid component cannot be overridden by air cooled components using the option "CoolingSetpointOnOffwithComponentOverride". The sequence of operation basically wanted the heatpumps to be turned off when the OutsideAir WetBulb temp < 10.7°C. I modelled the hydronic economizer as an “integrated economizer” and placed it on the same branch as the chilled water pump. Further, I created two separate schedules for the “PlantEquipmentOperationSchemes” (for cooling equipment list that comprises of only the air cooled gas heat pumps) and “CondenserEquipmentOperationSchemes” (For the condenser equipment list with the cooling tower). I added these schedules as EMS:Actuators that are updated at every timestep based on the OA WB Temp. This turned the heat pumps only when the OA WB Temp >10.7°C and simultaneously turned the cooling tower off (thereby overriding the economizer). The plant loop and condenser loop are as follows
I checked the ESO file and was able to verify that the air-cooled gas heatpumps were turned off when the economizer was operation and vice-versa. These results seem acceptable to me. If someone else has a better/alternative approach to go about overriding the hydronic economizer with air-cooled plant equipment, I would be very interested to know.
Raghu
