Free Cooling (Frcl); Hot Gas Bypass (Hgbp); Hot Water Control - Trane CVHE Installation, Operation And Maintenance Manual

Auto mode). Refrigerant gas is drawn out of the
evaporator by the compressor, where it is then
compressed and discharged to the condenser. Most of
the condensed refrigerant initially follows the path of
least resistance by flowing into the storage tank. This
tank is vented to the economizer sump through a small
bleed line; when the storage tank is full, liquid
refrigerant must flow through the bleed line restriction.
Because the pressure drop through the bleed line is
greater than that of the orifice flow control device, the
liquid refrigerant flows normally from the condenser
through the orifice system and into the economizer.

Free Cooling (FRCL)

To enable Free Cooling mode:
1. Install and commission Free Cooling.
2. Enable the Free Cooling mode in the Tracer®
AdaptiView™ Settings menu.
3. Press AUTO, and if used, close the external binary
input switch (connected to 1A20 J2-1 to 2) while the
chiller is in AUTO.
N N o o t t e e : : Free Cooling cannot be entered if the chiller is in
"STOP".
If the chiller is in AUTO and not running, the condenser
water pump will start. After condenser water flow is
proven, Relay Module 1A11 will energize operating the
Free Cooling Valves 4B12 and 4B13. The Free Cooling
Valves End Switches must open within 3 minutes, or an
MMR diagnostic will be generated. Once the Free
Cooling Valves End Switches open, the unit is in the
Free Cooling mode. If the chiller is in AUTO and
running powered cooling, the chiller will initiate a
friendly shut down first (Run: Unload, Post Lube, and
drive vanes closed). After the vanes have been
overdriven closed and condenser water flow proven,
the Free Cooling relays will be energized. To disable
Free Cooling and return to Powered Cooling, either
disable the Free Cooling Mode in the Tracer®
AdaptiView™ Settings menu if used to enable Free
Cooling, or OPEN the external binary input switch to
the 1A20 Module if it was used to enable Free Cooling.
Once Free Cooling is disabled, the Free Cooling relays
Relay Module 1A11 will de-energize allowing the Free
Cooling valves to close. The Free Cooling valves' end
switches must close within 3 minutes or an MMR
diagnostic is generated. After the end switches close,
the chiller will return to AUTO and powered cooling
will resume if there is a call for cooling based on the
differential to start.
N N o o t t e e s s : :
• The manual control of the inlet guide vanes
is disabled while in the Free Cooling mode
and the compressor is prevented from
starting by the control logic.
• The relay at 1A11-J2-4 to 6 is a FC auxiliary
relay and can be used as required.
CVHE-SVX02M-EN
S S t t a a r r t t - - u u p p a a n n d d S S h h u u t t - - d d o o w w n n

Hot Gas Bypass (HGBP)

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 shut-down. 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 Hot
Gas Bypass Cprsr Ctrl Command position. At this point,
the movement of the inlet guide vanes is stopped and
further loading/unloading of the chiller is controlled by
the opening/closing of the HGBP Valve (4M5). 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 the High Cprsr Rfgt Discharge
Temp Cutout 200°F (93.3°C) default, the chiller will shut
off on a MAR diagnostic. The chiller will reset
automatically when this temperature drops 50°F (10.0°
C) below the trip-point. HGBP is enabled in the Features
Menu Settings group of the Tracer® AdaptiView™
menus by enabling the option. The setting of the HGBP
Cut-In Vane Position is set-up at unit commissioning
via the service tool.

Hot Water Control

Occasionally, CenTraVac™ chillers are selected to
provide heating as a primary mission. With hot water
temperature control, the chiller can be used as a
heating source or cooling source. This feature provides
greater application flexibility. In this case, the operator
selects a hot water temperature and the chiller capacity
is modulated to maintain the hot water setpoint.
Heating is the primary mission and cooling is a waste
product or is a secondary mission. This type of
operation requires an endless source of evaporator
load (heat), such as well or lake water. The chiller has
only one condenser.
N N o o t t e e : : Hot Water Temperature Control mode does NOT
convert the chiller to a heat pump. Heat pump
refers to the capability to change from a cooling-
driven application to a heating-driven application
by changing the refrigerant path on the chiller.
This is impractical for centrifugal chillers as it
would be much easier to switch over the water
side.
This is NOT heat recovery. Although this feature could
be used to recover heat in some form, a heat recovery
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