Trane CVHH - Earthwise Purge Sequence of Operations; Purge Operating M Odes

Start-up and Shut-down
CVHH-SVX001A-EN 83
two weeks. This will prevent the accumulation of
air and noncondensables in the machine. To start
the purge, change the purge mode to ON in the unit
control “ Settings Purge” menu. Remember to turn
the purge mode to “Adaptive” after the two-hour
run time.
EarthWise Purge Sequence of
Operations
A Tracer UC800 controller that is configured to control a
purge system uses the operational sequences described in
this section.
Purge Operating Modes
Purge operating mode options are as follows:
Stop. The purge condensing unit does not run in this
mode.
On. The purge condensing unit runs continuously in this
mode, regardless of the chillers operational status.
Auto. The purge condensing unit runs in this mode, if the
main compressor of the chiller is operating.
Adaptive. The purge condensing unit operation depends
on past purge activity.
Adaptive Mode
The objectives of operating the unit in the adaptive mode
are to:
• Enable purge system operation
• Enable the refrigeration circuit to effectively
accumulate non-condensables whether or not the
chiller is running
• Provide information to an operator regarding whether
leakage is on the high-pressure or low-pressure side of
the chiller
• Decrease energy usage by running the purge
refrigeration circuit only when needed to remove non-
condensables, rather than running it continuously
The adaptive mode requires historical operating data so
that the controller can make optimal decisions regarding
how to run the purge refrigeration circuit in the future. On
initial start-up of a chiller that is in adaptive mode, the
purge refrigeration circuit runs continuously for 168 hours
(7 days). The chiller compressor may or may not be
running during this period.
Following the initial data collection period, the adaptive
mode customizes the purge refrigeration circuit operation
during two distinct chiller operating conditions:
• Chiller compressor On
• Chiller compressor Off
Adaptive Mode Process—Chiller Compressor
On
Figure 48, p. 84, illustrates the process described in this
subsection.
When the chiller com pressor starts, the purge refrigeration
circuit starts. The purge refrigeration circuit continues to
run until 60 consecutive minutes of running occur without
any pump-out of non-condensables. The Pumpout Time is
the greater of the following two values that the controller
has been tracking:
• The pump-out time with the chiller On, over the last
24 hours
• The average daily pump-out time with the chiller On,
over the last 7 days