Air Systems are modeled as either Central or Local systems. The type of air system determines the components that can be modeled as part of the system and how results are provided.

A Central system represents a single piece of remote equipment that serves many zones, or a single zone and represent typical equipment such as AHU, DOAS, RTU, Packaged Units etc. The common descriptor for a Central system is a single set of fans, coils, filters and other devices that condition air in a single location and distribute to various zones via a duct network.

Specific to loadmodeling.tool a Central system includes these inputs:

In addition Central systems can have the following optional inputs:

Central systems produce both Zone and Air System results. On the Results page each Air System will be shown in Load Results Air Systems Table. Selecting these systems will display the central component sizing (AHU Sizing) information. The Terminal Unit sizing and any Zone Components included on the system will be reported with the Zone.

A Local system represents an array of equipment, one for each zone assigned to the system. Typically these will be PTAC or PTHP systems or local ERV units. The common descriptor for a local system is multiple sets of fans, coils, filters and other devices that condition air locally at each zone.

Specific to loadmodeling.tool a Local system includes these inputs:

Local Systems produce only Zone results. On the Results Page each Zone will be shown in the Load Results Zones Table. Selecting any of these will show the zone sizing results, along with the Zone component sizing for all equipment created as part of that system. There will be no Air System results as there are no centralized components that are sized for Local Systems.