Trane CVHE Installation Instructions Manual page 38

Installation
constant value to be entered for this parameter must
be calculated for each specific individual chiller. This
calculated PC value takes into account how specific
compressor parameters such as the number of
compressor stages and average impeller diameter
affect the level of speed control dictated by the control
algorithm. Refer to the Figure below for the formula
used to calculate the PC constant value that needs to be
entered into this UCP2™ menu parameter, and an
example calculation.
Important: Using the actual specific average impeller
size of the chiller is critical for determining
an accurate value for the PC constant. If the
unit nameplate is missing, unreadable, or of
a vintage that did not include all of the data
categories, such as impeller size, contact
Trane Global Parts Technical Services. To
contact them, send a message to
ATechnicalService@trane.com. Provide the
chiller serial number and request a copy of
the shipped-with bill of materials for this
unit.
Figure 34. AF PC Constant formula and sample
calculation
6. AF Re-Optimization Factor: This factor is a
magnitude-based parameter for clearing the Surge
Flag. It is helpful to think of this value relative to the size
of the pressure error deadband. For example, with the
recommended deadband value of 0.03 in use and the
re-optimization factor set at the recommended value of
0.30, this sets the internal algorithm calculation to 10x
the deadband. This means that when encountering a
pressure error greater than 10x the deadband during
operation, it implies that the operating conditions have
changed enough to clear the Surge Flag.
a. The AF Re-Optimization Factor is adjustable from
0.03 to 1.0 in 0.01 increments. Optimal chiller
performance is most often achieved using the
recommend setting value of 0.30.
b. Setting a large re-optimization factor will cause this
feature to operate using the time-based parameter.
7. AF Re-Optimization Timer: This factor is the time-
based parameter for clearing the Surge Flag. The timer
38
begins to decrement from the front panel set point as
soon as surge occurs. The timer counts down as long
as the UCP2™ is powered. This value determines how
aggressively the chiller will try and re-optimize for
efficiency. For example, if the timer value is set to
1 hour, the Surge Flag will be cleared 1-hour after
being set.
a. The re-optimization timer is adjustable from 1 to
255 hours, in 1-hour increments. Optimal chiller
performance is most often achieved using the
recommend setting value of 24 (which equals
24 hours).
8. AF Boundary Pressure Coefficient (BPC) Y-
Intercept: The BPC Y-Intercept value is used to
determine the location of the BPC in the control
algorithm. This front panel value is unique because it
can be changed externally by the user, or internally by
the control algorithm.
a. BPC Y-Intercept is adjustable for 0.01 to 2.0 in 0.01
increments. Value = 0.4 is recommended.
9. AF Boundary Pressure Coefficient (BPC) Y-
Intercept Maximum: The BPC Y-Intercept is never
allowed to exceed a set maximum value. This value is
a manual way to control the aggressiveness of the
efficiency optimizing procedure.
a. As this value is lowered the probability of
encountering surge decreases but so does the
potential efficiency improvement at a given
operating condition.
b. The maximum boundary pressure setpoint is
adjustable from 0.01 to 2.0 in 0.01 increments. The
recommended value is 2.0.
10. AF Pressure Error Deadband: Anytime the Pressure
Coefficient (PC) is inside of the pressure deadband, no
further speed reductions are allowed. Thus, the
pressure deadband establishes a region where no
background speed decreases will occur.
a. Setting this value large will tend to make the AFDB
control algorithm less aggressive at optimizing
efficiency.
b. The pressure error deadband is adjustable from
0.001 to 1.000 in increments of 0.001. The
recommended value to use that has shown to most
often contribute to optimal chiller operation is
0.030.
11. AF Proportional Speed Gain: The proportional
speed gain is used to convert the pressure error
calculated by the control algorithm into Delta Hz. The
proportional speed gain is adjustable from 1 to 100 in
increments of 1. The recommended setting value is 50.
AFDH-SVN03H-EN