ACS 400 User’s Manual 157
Appendix B
ACS 400 Pump and Fan Control (PFC) Macro
Introduction
The Pump and Fan Control (PFC) macro can operate a pump (or fan or compressor) station with
one to four parallel pumps. The control principle of a two-pump station is as follows:
• The motor of pump no. 1 is connected to the ACS 400. The capacity of the pump is controlled
by varying the motor speed.
• The motor of pump no. 2 is connected direct on-line. The pump can be switched on and off by
the ACS 400 when necessary.
• The process reference and actual value are fed to the ACS 400 PID controller. The PID
controller adjusts the speed (frequency) of the first pump such that the process actual value
follows the reference. When the frequency reference of the process PID controller exceeds the
limit set by the user, the PFC macro automatically starts the second pump. When the frequency
falls below the limit set by the user, the PFC macro automatically stops the second pump.
• Using the digital inputs of the ACS 400, an interlocking function can be implemented; the PFC
macro detects if a pump is switched off and starts the other pump instead.
• The PFC macro makes automatic pump alternation possible. Thus each pump can be run with
an equal duty time. For more information on the alternation system and the other useful
features such as Sleep function, Constant reference value, Reference steps and Regulator by-
pass, see parameter group 40, 41 and 81 parameter descriptions.
As default when PFC macro is selected, the ACS 400 receives the process reference (setpoint)
through analog input 1, process actual value through analog input 2 and Start/Stop commands
through digital input 1. The interlocks are connected to digital input 4 (speed regulated motor) and
digital input 5 (constant speed motor). A Run Enable signal is received through the digital input 2
and the PFC control is activated/deactivated through the digital input 3. The default output signal is
given through the analog output (frequency).
Normally the automatic Pump and Fan Control is bypassed when the ACS 400 is in local control
(LOC is shown on the control panel display). In this case, the process PID controller is not in use
and the constant speed motors are not started. However, by selecting value 2 (
REF2 (%)) for
parameter 1101
KEYPAD REF SEL PFC reference can be given from the control panel in local control.
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