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CVHE-SVU01E-EN
General
Information
Hot Gas Bypass
The hot gas bypass (HGBP) control
option is designed to minimize
machine cycling by allowing the
chiller to operate stably under
minimum load conditions. In these
situations, the inlet guide vanes are
“locked” at a preset minimum
position, and unit capacity is
governed by the HGBP valve actuator.
Control circuitry is designed to allow
both the inlet guide vanes and the
HGBP valve to close for unit
shutdown.
After a chiller starts and is running
the inlet guide vanes will pass
through the HGBP Cut-In-Vane
position as the chiller starts to load.
As the chiller catches the load and
starts to unload, the inlet guide vanes
will close to the HGBP Cut-In Vane
position. At this point the movement
of the inlet guide vanes is frozen and
further unloading of the chiller is
controlled by the opening of the
HGBP Valve 4M5 and module
modulates the HGBP valve at low
loads. When the control algorithm
determines the chiller to be shut
down, the inlet guide vanes will be
driven fully closed, and the HGBP
valve will be driven closed. After the
inlet guide vanes are fully closed the
chiller will shut down in the Friendly
mode. Chillers with HGBP have a
discharge temperature sensor (4R16)
monitoring the discharge gas
temperature from the compressor. If
this temperature exceeds 200°F, the
chiller will shut off on a MAR
diagnostic. The chiller will reset
automatically when this temperature
drops 50°F below the trip-point.
HGBP is enabled in the Features
menu settings Group of the DV
Menus by enabling the option. The
setting the HGBP Cut-In Vane
Position is setup at unit
commissioning via the service tool.