potential to reduce energy consumption without sacrificing
thermal comfort and IAQ by combined (optimal) control of
both the VRF part and the VAV part (Zhu et al., 2014b).
It is found that the OA supply temperature affects the
combined system significantly. When the OA supply temperature
is lower than the indoor air temperature, the OA takes
parts of the internal loads, and the loads should be taken by the
VRF unit, i.e. cooling capacity of the VRF unit is decreased.
Otherwise, the VRF unit should take part of the OA load and the
cooling capacity should be increased. Therefore, varying OA
supply temperature will result in a reciprocal relationship between
the cooling capacity of the VRF unit and the OAP unit,
which leads to varying energy efficiency of the system as well.
Energy consumption of the combined systemcan beminimized
by optimizing the OA supply temperature. However, how to
obtain the optimal OAsupply temperaturewas not discussed in
(Zhu et al., 2014b). As an extension study, this paper mainly
presents a simplified OA supply temperature optimal control
strategy and analyzes energy saving potentials of the combined
system. The predicting models for energy consumption of the
VRF unit and the OAP unit are developed in this study, and they
are used to obtain the optimal load allocation between the VRF
unit and the OAP unit. The optimal control strategy changesOA
supply temperature according to the optimal load allocation in
order to minimize the total energy consumption of the combined
system. The proposed optimal control strategy is tested
and evaluated in a simulated multi-zone office building under