The Supervisory control for conventional unitary air conditioning system is conceptually
designed based on Programmable Logic Control (PLC) system. The advantage of PLC
system is that it allows online monitoring continually and updates or modification can be
performed interactively. This supervisory mode is applied to the conventional unitary air
conditioner to avoid the frequent interruption or adjustment of the fan speed or
temperature set point by users normal practice which has contributed to the surge of
energy consumption due to the frequent on/off of the compressor. Three experiments
have been performed at different control methods to simulate user’s daily practice. The
first control method is the Variable Set point with high speed fan, the second control
method is the Fixed Set point with high speed fan and the third control method is a
Supervisory Control; a fixed set point with variable fan speed. The experiments have
been conducted for eight (8) hours and the statistic data of accumulated energy
consumption based on one unitary air conditioner with capacity of 1 Horse Power are
acquired and sampled at the time interval of 30 minutes for the analysis. From these
experiments, the supervisory control has consumed 4.2 kWh per day which is 82.35%
compared to normal consumption of 5.1 kWh. This result translated into 0.9 kWh or
17.65% of total energy saving per day. The consistency of the air compressor operation in
this control method has become a major factor in achieving indoor temperature steadiness
whilst improving the energy savings