Typically used in the residential buildings and non fancy hotels especially in the US. Central Outdoor-Air Handling Unit provides 100% of Outside Air to the zone meaning all air that is going through the unit is only the Outside Air, there is no mixing with the return air. All exhaust air from the zones goes to the Heat Recovery unit where Outside Air that we are introducing to the building is preheated or precooled depending on the season.

If heat recovery effectiveness is zero that practically means that DOAS doesn’t have the heat recovery. If “Design Air Flow” for the “Central Outdoor-Air Handling Unit” is zero that practically means that there is no “Central Outdoor-Air Handling Unit”.

User decides on how much outside air will be supplied to the building. This is done via “Design Air Flow” slider.

Please note that even though that we are providing the possibility to bring outside air via DOAS, it is not very usual to have DOAS system with PTAC system. Outside air for PTAC systems is usually provided locally via PTAC itself like it is shown on the picture below.

Default values:

• Hot Water Pump power: 21 W/gpm or 1.32 W/(L/s)
• PTAC Fan Power: 0.2 W/cfm or 0.095 W/(L/s)
• DOAS Fan Power: 0.9 W/cfm or 0.4 W/(L/s)
• DOAS heat recovery type: Enthalpy
• Hot-water pumps are VSD
• Night time operation: Cycle on any load