ASHRAE Cooling Sizing

In the ASHRAE cooling sizing method the cooling design load calculations are carried out using the standard ASHRAE Heat Balance method implemented in EnergyPlus using the 'Purchased air' system type. You can define the conditions of the supply air delivered to cooled zones using Design supply temperature and Supply air humidity ratio. The total (sensible + latent) load is calculated as the enthalpy change between the zone return air and the specified supply air condition for the current load.

The ASHRAE system is modelled assuming:

No economiser,
No heat recovery,
No heating,
Zero pressure rise fan,
No humidification/dehumidification,
Zone plenums will not be used if specified,
Outside airflow rate and operation schedule defined by the data under the Mechanical Ventilation header on the HVAC tab at the zone level,
Cooling coil availability defined by the schedule under the Cooling header on the HVAC tab at the zone level,
Zone design cooling temperature setpoints are defined by the data under Environmental Control on the Activity tab.

Unlike the other 3 cooling sizing options, 1-ASHRAE cannot be used in conjunction with Natural ventilation.

Design supply temperature

The constant dry-bulb air temperature of the air supplied for cooling the zone.

Supply air humidity ratio

The constant humidity ratio (mass of water per mass of dry air) of the cold supply air. The default humidity ratio is 0.009.