Duct-free split hvac system with mixed-mode operation

A split heating, ventilation, and air-conditioning system including a single outdoor unit (ODU) configured to circulate refrigerant to a plurality of indoor units (IDUs) for heat exchange, the system having a controller configured to perform operations, the operations comprising:

• transmitting, to the ODU, a first command signal from one or more IDUs of the plurality of IDUs, the first command signal corresponding to a first operating mode, wherein a first IDU of the plurality of IDUs corresponds to the first command signal corresponding thereto;
• setting, at the ODU, the first operating mode based on the first command signal;
• transmitting, to the ODU, a second command signal from at least one IDU of the plurality of IDUs, and fewer than all IDUs of the plurality of IDUs, and while one or more IDUs of the plurality of IDUs is the first IDU corresponding to the first command signal, the second command signal corresponding to a second operating mode, wherein a second IDU of the plurality of IDUs corresponds to the second command signal corresponding thereto, and wherein the first and second operating mode correspond to either a cooling mode or a heating mode, and wherein the first and second operating mode are dissimilar to one another;
• setting, at the ODU, the second operating mode based on the second command signal;
• operating the ODU and the second IDU in the second operating mode based on the second command signal;
• and
• permitting, at the ODU after operating the ODU in the second operating mode, the first operating mode based on the first command signal.