Trane CVGF - Manual (Page 15)

1 5 CTV-PRC001-GB
Extended Operation Package
Select the extended-operation package
for chillers that require
external, hot
water control, and/or base-loading
capabilities. This package also includes
a 4-20 mA or 0-10 Vdc analog input for
a refrigerant monitor.
• External base-loading control input
• External base-loading setpoint
• External hot-water control input
• Refrigerant monitor input
Base-Loading Control
This feature allows an external
controller to directly modulate the
capacity of the chiller. It is typically used
in applications where virtually infinite
sources of evaporator load and
condenser capacity are available and it
is desirable to control the loading of the
chiller. Two examples are industrial
process applications and cogeneration
plants. Industrial process applications
might use this feature to impose a
specific load on the facility’s electrical
system. Cogeneration plants might use
this feature to balance the system’s
heating, cooling, and electrical
generation.
All chiller safeties and Adaptive Control
functions are in full effect when Base
Loading is enabled. If the chiller
approaches full current, the evaporator
temperature drops too low, or the
Controls
condenser pressure rises too high, the
controller’s Adaptive Control logic
limits the loading of the chiller to
prevent the chiller from shutting down
on a safety limit. These limits may
prevent the chiller from reaching the
load requested by the Base Loading
signal.
An alternative and less radical
approach to Base Loading indirectly
controls chiller capacity. Artificially
load the chiller by setting the chilled-
water setpoint lower than it is capable
of achieving. Then, modify the chiller’s
load by adjusting the current-limit
setpoint. This approach provides
greater safety and control stability
because it leaves the chilled-water
temperature-control logic in effect.
The chilled-water temperature control
responds more quickly to dramatic
system changes and limits chiller
loading prior to reaching an Adaptive
Control limit.
Hot-Water Control
This feature allows an external
controller to enable/disable and
modulate the hot-water control mode.
Occasionally, centrifugal chillers are
used to provide heating as a primary
mission. In this case the external
controller or operator would select a
hot-water temperature setpoint and the
chiller capacity would be modulated to
maintain the setpoint. Heating is the
primary mission and cooling is a waste
product or a secondary mission.
This technique provides application
flexibility, especially in multiple-chiller
plants in conjunction with undersized
heating plants.
The chiller needs only one condenser
for hot-water control, whereas Heat
Recovery uses a secondary condenser.
Refrigerant Monitor
The Extended Operation package
allows for a refrigerant monitor to send
a 4-20 mA signal to the DynaView
display. It can be calibrated to
correspond to either 0-100 ppm or 0-
1,000 ppm concentration levels.
The concentration level is displayed at
DynaView, but the chiller will not take
any action based on the input from the
refrigerant monitor.
Alternatively, a refrigerant monitor can
be connected to Tracer Summit, which
has the ability to increase ventilation in
the equipment room in response to
high refrigerant concentrations.
Optional
Features