A PID (Proportional Integral Derivative) controller is
usually used to control variable speed drives (VSD) in
HVAC systems. This controller can be part of the
Building Management System, part of an OEM
device such as an Air Handling Unit or Pump
Controller, or part of the frequency converter (VSD).
The PID controller monitors the
examining signals, called Feedback signals, that are
transmitted from sensors placed in the system and
comparing them with their expected value or
Setpoint. The PID controller then adjusts the speed
of the variable speed drive until the Feedback signal
equals the Setpoint.
While many VSD’s contain a PI or PID controller,
they are often too complicated to set up and do not
have the capability needed for HVAC applications.
As a result, an external PID controller may be
needed. This increases the cost and complexity of
the installation. The PID controller in the VLT® 6000
has been specifically designed for HVAC applications
to provide full functionality and simple programming.
The terminology used in connection to the PID
controller is well known within the HVAC industry.
Feedback and setpoint settings can directly be done
in the most common units such as Pa, PSI, m³/h,
CFM, °C, °F etc.
Two Zone control, for example, is an important
feature for HVAC applications which is not required
for most industrial applications. In HVAC systems, it
is frequently necessary to monitor two feedback
signals. The VLT® 6000 is capable of handling the
traditional single feedback with a single setpoint as
well as two feedbacks with a single setpoint, and
two feedbacks with two setpoints.