A split DOAS unit is a type of dedicated outdoor air system (DOAS) that is designed to condition outdoor air and can be used in conjunction with a variable refrigerant flow (VRF) or variable refrigerant volume (VRV) system[1][2][3][4][5]. Split DOAS units are available as packaged equipment or as a split system to support decoupled designs[1][5]. With split-system DOAS, architects and building owners can separate and strategically arrange VRF outdoor units and DOAS equipment, which offers more design freedom than packaged equipment[1].
Split DOAS units typically include an enthalpy sensor in the return air stream, before the cooling coil, to manage the system logic based on the outdoor air conditions[2]. They can be integrated with VRF systems in a design where ventilation is ducted directly from the DOAS to the VRF indoor units[1]. This approach requires additional design considerations when both the DOAS and the VRF system use variable speed fans[1].
Split DOAS units offer many benefits, including energy savings and performance optimization when working with VRF systems[4]. They can also save on the required cooling and heating tonnage, which is increasingly important to facility managers[5]. In response to the growing demand for energy-efficient ventilation, some manufacturers now offer split-system and packaged DOAS equipment with inverter-driven compressors[1][5].
Citations:
[1] https://www.mitsubishicomfort.com/sites/default/files/2021-05/DOAS%20and%20VRF%20White%20Paper.pdf
[2] https://www.samsunghvac.com/commercial/split-doas
[3] https://www.esmagazine.com/articles/101656-split-dedicated-outdoor-air-systems-lg-air-conditioning-technologies-usa
[4] https://lghvac.com/resource-service?filename=EM_Split_Compact_DOAS.pdf
[5] https://www.achrnews.com/articles/139745-utilizing-vrf-and-doas-for-high-performance-building-applications
[6] https://www.ambientedge.com/faqs/what-is-the-difference-between-vrf-and-split-ac/
