Hot Water Control; Cvhe-Svx02H-En; Heat Recovery Cycle - Trane CVHE Installation, Operation And Maintenance Manual

Start-up and Shut-down
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 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 200°F (93.3°C), 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 the HGBP Cut-In Vane Position is setup at unit
commissioning via the service tool.

Hot Water Control

Occasionally CTV 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.
Note: 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 unit has
a second heat exchanger on the condenser side.
The Tracer AdaptiView Main Processor provides the hot
water temperature control mode as standard. The leaving
condenser water temperature is controlled to a hot water
setpoint between 80°F and 140°F (26.7° and 60.0°C). The
leaving evaporator water temperature is left to drift to
satisfy the heating load of the condenser. In this
application the evaporator is normally piped into a lake,
well, or other source of constant temperature water for the
purpose of extracting heat. In hot water temperature
control mode all the limit modes and diagnostics operate
as in normal cooling with one exception; the leaving
condenser water temperature sensor is an MMR
diagnostic when in hot water temperature control mode.
66
(It is an informational warning in the normal cooling
mode.)
In the hot water temperature control mode the differential-
to-start and differential-to-stop setpoints are used with
respect to the hot water setpoint instead of with the chilled
water setpoint. The control panel provides a separate
entry at the Tracer AdaptiView to set the hot water
setpoint. Tracer AdaptiView is also able to set the hot water
setpoint. In the hot water mode the external chilled water
setpoint is the external hot water setpoint; that is, a single
analog input is shared at the 1A16-J2-5 to 6 (ground).
An external binary input to select external hot water
control mode is on the EXOP OPTIONAL module 1A18
terminals J2-3 to J2-4 (ground). Tracer AdaptiView also
has a binary input to select chilled water control or hot
water temperature control. There is no additional leaving
hot water temperature cutout; the HPC and condenser
limit provide for high temperature and pressure
protection.
In hot water temperature control the softloading pulldown
rate limit operates as a softloading pullup rate limit. The
setpoint for setting the temperature rate limit is the same
setpoint for normal cooling as it is for hot water
temperature control. The hot water temperature control
feature is not designed to run with HGBP , AFD, free
cooling, or ice making.
The factory set PID tuning values for the leaving water
temperature control are the same settings for both normal
cooling and hot water temperature control.

Heat Recovery Cycle

Heat recovery is designed to salvage the heat that is
normally rejected to the atmosphere through the cooling
tower, and put it to beneficial use. For example, a high-rise
office building may require simultaneous heating and
cooling during the winter months. With the addition of a
heat recovery cycle, heat removed from the building
cooling load can be transferred to areas of the building that
require heat.
Note: The heat recovery cycle is possible only if a cooling
load exists to act as a heat source.
To provide a heat recovery cycle, a heat-recovery
condenser is added to the unit. Though physically identical
to the standard cooling condenser, the heat-recovery
condenser is piped into a heat circuit rather than to the
cooling tower. During the heat recovery cycle, the unit
operates just as it does in the cooling only mode except
that the cooling load heat is rejected to the heating water
circuit rather than to the cooling tower water circuit. When
hot water is required, the heating water circuit pumps
energize. Water circulated through the heat-recovery (or
auxiliary) condenser tube bundle by the pumps absorbs
cooling-load from the compressed refrigerant gas
discharge by the compressor. The heated water is then
used to satisfy heating requirements.

CVHE-SVX02H-EN