Separating Ventilation Loads v. Zone Loads[LINK]

Can I determine the ventilation load for PAU in PAU + FCUs system? If can, how to split the total cooling load into room load and ventilation load for PAU sizing in energyplus?

In the HTML report, “Nominal total capacity [W]” (EquipmentSummary) and “Design Load [W]” (HVACSizingSummary) can be found. Are they equal to “Total cooling load” and “Room load”? (i.e. Ventilation load = “nominal total capacity” - “Design Load”)

PAU – Primary Fresh Air Handling Unit or DOAS – Dedicated Outdoor Air Unit

FCU – Fan Coil Unit

There are several ways to split the total cooling load into room load and ventilation load for PAU sizing in EnergyPlus:

1) In the eio output, section, the heating and cooling loads reported there are the peak *sensible* loads for each zone, without any ventilation load. These are the same values reported as “Design Load” in the HVACSizingSummary table report.

2) In the EquipmentSummary table report, the component capacities reported there are the total (cooling, sensible for heating) output capacities include any ventilation load if it impacts that component.

3) If you have a central air loop that serves only the ventilation load, and zone equipment that serves only the zone load, there is an autosizing option in Sizing:System that should autosize the central system appropriately.

From example file 5ZoneCoolBeam.idf:

Sizing:System,
  VAV Sys 1, !- AirLoop Name
  VentilationRequirement, !- Type of Load to Size On
  autosize, !- Design Outdoor Air Flow Rate {m3/s}
  1.0, !- Minimum System Air Flow Ratio

When you run a simulation, if you want to report ventilation loads, the following Output:Variable names are available:

• HVAC,Sum,Zone Mechanical Ventilation No Load Heat Removal [J]
• HVAC,Sum,Zone Mechanical Ventilation Cooling Load Increase [J]
• HVAC,Sum,Zone Mech Ventilation Cooling Load Increase: OverHeating [J]
• HVAC,Sum,Zone Mechanical Ventilation Cooling Load Decrease [J]
• HVAC,Sum,Zone Mechanical Ventilation No Load Heat Addition [J]
• HVAC,Sum,Zone Mechanical Ventilation Heating Load Increase [J]
• HVAC,Sum,Zone Mech Ventilation Heating Load Increase: OverCooling [J]
• HVAC,Sum,Zone Mechanical Ventilation Heating Load Decrease [J]