44
Centrifugal Chillers
IM 1044-2
Hot Gas Bypass
All units can be equipped with an optional hot gas bypass system that feeds discharge gas directly into the
evaporator when the system load falls below 10% compressor capacity.
Light load conditions are signaled by measurement of the percentage of RLA amps by the MicroTech II
controller. When the RLA drops to the setpoint, the hot gas bypass solenoid valve is energized, making hot gas
bypass available for metering by the hot gas regulating valve. This hot gas provides a stable refrigerant flow and
keeps the chiller from short cycling under light load conditions. It also reduces surge potential on heat recovery
units.
The factory setpoint for bringing on hot gas bypass is 40% of RLA.
Condenser Water Temperature
When the ambient wet bulb temperature is lower than design, the entering condenser water temperature can be
allowed to fall, improving chiller performance. See page 7 for details.
Daikin
chillers will
start
with entering condenser water temperature as low as 55
°
F (42.8
°
C) providing the
chilled water temperature is below the condenser water temperature.
The minimum
operating
entering condenser water temperature is a function of the leaving chilled water
temperature and load.
Even with tower fan control, some form of water flow control such as tower bypass must be used.