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Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.8.5153
Figure 11-2. Step Control Screen
Section 11 • Condenser Control
selected as Low Speed Fan through combo box. E.g.:
Let’s say Out #2 is selected as Low Speed Fan in Step
2. When step 2 becomes active during condenser
control operation which is after Step 2 time-out de-
lay, Out #2 is left off for time as set by the operator in
High to Low Speed Delay. After low speed fan ener-
gizes, then timer for Step 3 starts timing.
Control:
• Toggle any of the steps On/Off during Manual opera-
tion of Condenser Control. This button is active only
when Run Mode selected is Manual. During Auto op-
eration of Condenser Control, control button for ac-
tive step will be “ON”.
VFD Settings
This page is active only when Condenser VFD is selected
in Confi guration Screen. When a VFD Fan is used for con-
denser control operation, the speed of the VFD is con-
trolled using PID algorithm.
P = Proportional (gain):
• Used to adjust the fan speed action in direct propor-
tion to the difference between the control setpoint
and the process variable (SP - PV = error). The pro-
portional term is a unit less quantity and is used for
coarse adjustment. This setpoint should be set to the
lowest value that gives adequate control system re-
sponse. Increasing the proportional setting increases
the control system’s sensitivity to small process fl uc-
tuations and the tendency to hunt.
I = Integral (reset):
• Used to adjust the capacity control action, integrat-
ing the error over time, to account for a small er-
ror that has persisted for a long time. This quantity
is used for fi ne adjustment. This setpoint is used to
smooth out process variations. This setpoint should
be set high enough to prevent hunting but not too
high or it will cause control system overshoot.
D = Derivative (rate):
• Used to adjust the capacity control action, account-
ing for how fast the error is changing, positively or
negatively.
Maximum Speed:
• This setpoint defi nes the maximum speed in percent-
age for Condenser VFD Fan at which it should run
for continuous step delay time to increase condens-
er steps. E.g. let’s say setpoint is kept at 95%. Then
condenser VFD fan will have to run at speed of 95%
or more to advance to next step. Maximum Speed
can be set as 100%, which is when analog output (at
which condenser VFD fan is connected) reaches to
20mA in its normal range of 4-20 mA
Minimum Speed:
• This setpoint defi nes the minimum speed in percent-
age for Condenser VFD Fan at which it should run for
continuous step delay time to decrease condenser
steps. E.g. let’s say setpoint is kept at 5%. Then con-
denser VFD fan will have to run at speed 5% or less to
advance to next step. Minimum Speed can be set as
0%, which is when analog output (at which condens-
er VFD fan is connected) reaches 4mA in its normal
range of 4-20 mA.