在正常操作模式下，其控制系統依據車廂內熱負荷要求控制車廂內4個壓縮機啟閉，因此每個車廂中製冷能力分為25%、50%、75%、100%，共四級，用以調整車內至所需的 25±1°C 及相對濕度60%舒適環境。控制系統並有執行所有特定控制與自我測試功能，可將故障與診斷資料可以下載至筆記型電腦，便於維修人員判讀故障及維修。
The TIAA MRT Project adopted the Roof-mounted Air Conditioning System for A/C in the EMUs. Every passenger coach is equipped with two A/C units which are located respectively in the front and back end of the ceiling. The A/C unit is weighed 685 kg, equipped with two horizontal compressors and operated through an electrical control panel. The system is installed with normal operation mode, emergence ventilation mode, and smoke mode. It is also equipped with air cooling, air purification, system self-check and system protection functions. Under normal operation mode, A/C power is provided through auxiliary power supply. When encountering power failure, the emergency inverter converts power supply into 110V DC battery power which can perform emergence ventilation for at least 30 minutes.
There are four compressors in each coach which can be controlled to operate according to interior thermal loads. Under normal mode operation, the cooling capability can be adjusted to 25%, 50%, 75% or 100% level by controlling the compressors to provide a most comfortable environment of 25±1°C and R.H. 60%. The control system can also perform all specific controls and self-test functions and auto-save malfunction/ diagnosis records accordingly. The maintenance crew can download the malfunction/ diagnosis records onto their laptops for trouble shooting and maintenance actions.
Every A/C unit is equipped with two Fresh/ Emergence Air Dampers and one Return Air Dampers. Under normal operation mode, Fresh/Emergence Air Dampers are partially opened and the Return Air Dampers is fully opened. When train loses traction power supply or when two A/C units encounter high pressure trip, the system switches to Emergency Ventilation Mode in which Fresh/ Emergence Air Dampers are fully opened and the Return Air Dampers is fully closed to force 100% fresh air into the coach. During Emergency Ventilation Mode, the Exhaust Air Outlet at car body will automatically open to emit excessive air and avoid excessive wind pressure in the coach. When there's a fire outside the coach, the system switches to Smoke Mode in which Fresh/ Emergence Air Dampers and Air Extraction Doors are fully closed and the Return Air Shield is fully opened to avoid smoke into the coach.
The TIAA MRT EMUs adopted R407C refrigerant for the A/C System which is in accordance with Montreal Protocol regulations. The modular design of the A/C system results in faster replacement/maintenance actions and shorter suspension periods for train maintenance. Moreover, the multiple operation modes can provide better service quality and traveling environment for passengers.