Trane CVGF-SVU02B-E4 Operation And Maintenance Manual page 45

Tracer Base Loading
The Tracer commands the chiller
to enter the base load mode by
setting the base load mode
request bit ON. If the chiller is
not running, it will start
regardless of the differential to
start. While the unit is running in
base loading, it will report that
status back to the Tracer. When
the Tracer removes the base
load mode request, the unit will
continue to run, using the
normal chilled water control
algorithm, and will turn off, only
when the differential to stop has
been satisfied.
CVGF-SVU02B-E4
Base Loading
Control Algorithm
External Base Base Loading
The CH530 accepts 2 inputs to
work with external base loading.
The binary input is at 1A18
Terminals J2-1 and J2-2
(Ground) which acts as a switch
closure input to enter the base
loading mode. The second input,
an analog input, is at 1A17
terminals J2-2 and J2-3 (Ground)
which sets the external base
loading setpoint, and can be
controlled by either a 2-10Vdc or
4-20mA Signal. At startup the
input type is configured.
The graphs in Figure 16 show
the relationship between input
and percent RLA. While in base
loading the active current limit
setpoint is set to the Tracer or
external base load setpoint,
providing that the base load
setpoint is not equal to 0 (or out
of range). If it is out of range, the
front panel current limit setpoint
is used. During base loading, all
limits are enforced with the
exception of current limit.
DynaView ™ displays the
message "Unit is Running Base
Loaded."
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 method provides
greater safety and control
stability in the operation of the
chiller because it has the
advantage of leaving the chilled
water temperature control logic
in effect.
The chilled water temperature
control logic responds quicker to
dramatic system changes, and
can limit the chiller loading prior
to reaching an Adaptive Control
limit point.
45