Unit installation

49
CAPACITY CONTROL STEPS
Capacity control is achieved by cycling compressor ON/OFF and slider capacity control valve. On multiple compressor
units, capacity is controlled by a combination of slider capacity control valve and compressor staging.
These chillers are equipped with
stepless capacity control system on compressors as a standard feature for
very accurate response to load requirements and best part load efficiency. Each compressor is equipped with a slider
controller that enables to modulate capacity between 25% to 100%, thus giving a broad range to control total chiller
capacity between 10% to 100% on an average. This system has tremendous advantages such as infinite capacity
modulation allowing the compressor capacity to exactly match the cooling load, reduced compressor cycling which
leads to better operationally reliability and reduced operating costs.
Optionally these chillers can be provided with 4-step capacity control on compressors for stepped load shedding as
required by most energy management systems and suited to systems with high inertia. In this case, the capacity
control steps are as follows:
% FULL LOAD
MODEL
NUMBER
STEP CAPACITY CONTROL
(option-I)
STEP CAPACITY CONTROL WITH HGBP
(option-II)
ASQ045B-ASQ070B
100-50-OFF 100-50-HGPB-OFF
ASQ080B-ASQ150B
100-75-63-50-25-OFF 100-75-63-50-25-HGBP-OFF
ASQ160B-ASQ200B
100-83-66-50-33-16-OFF 100-83-66-50-33-16-HGBP-OFF
ASQ220B-ASQ280B
100-87-75-63-50-37-25-12-OFF 100-87-75-63-50-37-25-12-HGBP-OFF
ASQ300B-ASQ440B
100-92-83-75-66-58-50-42-33-25-16-8-OFF 100-92-83-75-66-58-50-42-33-25-16-8-HGBP-OFF
NOTES:
1. All models have slider capacity control valve on all compressors.
2. HGBP = Hot gas bypass available on lead compressor for all models (option).
3. HGBP modulates to approximately 80% of its compressor lowest unloaded capacity.
UNIT SHUTDOWN
The unit can be stopped at any time by switching the unit ON/OFF key on the keypad and the ON LED is off.
The compressor oil heaters will energize to prevent refrigerant condensing in the compressor crankcase and to
prevent the compressor oil becoming saturated with refrigerant. If ambient temperatures are low, the cooler heater (if
provided) will also energize to prevent the possibility of liquid freezing in the vessels. The mains power to the unit
should normally be NOT switched OFF, even when the unit is not required to run. If main power must be switched
OFF, (for extended maintenance or a shutdown period), the compressor suction, discharge and other service valves
should be closed and if there is a possibility of liquid freezing due to low ambient temperatures, the cooler should be
drained. The closed valves should be opened and power must be switched on for at least 24 hours before the unit is
restarted.