HVAC tab in model data HVAC tab - Compact HVAC
The data required to define the heating system will depend on whether the HVAC model option is set to Simple or Compact and if set to Compact the type of Compact HVAC system selected.
The heating capacity can either be entered by hand or can be Autosized using the Heating Design Calculations. By default, if immediately prior to a Simulation the heating capacity has not been entered (neither by hand nor from a previous Heating design calculation) then a Heating design autosizing simulation is started to calculate the capacity. The Plant sizing building model option controls the way this works.
You can change heating capacities by hand if you wish but you should bear in mind that, by default, if Model Options change, all heating and cooling capacities are reset to zero. Set the Plant sizing model option to '2-Manual' to avoid this happening.
If the HVAC system is Unitary multizone then the central heating coil capacity is calculated as the sum of the individual zone heating energy requirements.
At building level you can select the boiler to be used to provide hot water to FCU heating coils. Only one boiler can be specified for the whole building, i.e. there is only a single hot water circuit served by one boiler in Compact HVAC simulations.
When preheat is specified, this data defines the temperature of the air coming off the FCU heating coils assuming idealised control. Preheat coils are automatically sized by EnergyPlus before the simulation to provide this off coil temperature given the flow rates in the air handling unit.
This schedule data is used in conjunction with the heating setpoint temperatures on the Activity tab to define the time-varying heating setpoint schedule in the zone. The operation schedule defines the times when full and setback setpoints should be met and the setpoint data on the Activity tab define the actual setpoint values. See Defining setpoint temperature schedules for more on this.