This paper reports the results of experimental work along with numerical simulation of a simplified re-commissioning approach for existedmultiple-chiller systems serving institutional building working on a hot climate. The simplified approach that composed of some operation strategiesrequires simple measurements, experimentation and analysis with minimal additional cost. These strategies include: selecting the most efficientcombination of chillers and compressors; operating chillers schedule during working and non-working hours; reducing chillers capacity whenworking during summer vacation or summer semester; and finally adjust the chilled water flow rate to be adequate for the building load. Thesimplified re-commissioning approach improves the overall system performance that results in a total energy saving of about 7.81% of the annualHVAC consumption.