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20 Direct-Fired Indoor and Outdoor Units • MUA-SVP01A-EN
Functions
User Configured PID Control
This function is applicable to non-recirculating units only. The User Configured
PID Control function allows the user to control an analog output based on a user
defined analog input and setpoint. See the Typical Wiring and Unit Controller
Specification sections of this manual for more information regarding the inputs
and outputs. This function also allows the user to select the PID type (direct or
reverse acting) and establish upper and lower control limits. Five keypad entries
define the operational parameters. These parameters are: User Control Setpoint,
Minimum User Setpoint, Maximum User Setpoint, Low Input Value, and High
Input Value. The low and high input values describe the input transducer range.
The control setpoint is the primary operational parameter while the minimum
and maximum setpoints describe the extents of the desired operating range and
provide secondary control as described below. The allowable range for all of
these parameters is -9999.99 - +99999.99.
The analog input and output are polarity sensitive and can be configured for
different types of inputs. See the Typical Wiring and Unit Controller Specification
sections of this manual for more information regarding the inputs and outputs.
The analog input must be connected to IN-1. This input must be configured for
either of two different types of input signals:
• 0-5Vdc: The output impedance must not exceed 10K?. The input impedance
of the controller is 1M?. This input is polarity sensitive. Be sure the
connections from the source are correctly polarized at the controller.
• Thermistor: Precon type 2 (10k ohm at 77°F) Input voltages should range
between 0.489V and 3.825V. See the wiring diagrams for recirculating model
units for typical connections of transducers.
• The IN-1 configuration jumpers on the controller must be set for the
appropriate input signal.
A contact closure between the appropriate terminals on the unit's
terminal strip located in the unit's main control panel will drive the
output to 100%. See the Typical Wiring Schematic and Multiplexed Input
sections of this manual for more information.
DIRECT ACTING
The controller output is modulated by a PID loop from 0% to 100% based on the
User Control setpoint and the input signal. As the input signal increases the
output voltage increases. Additionally, a secondary control acts to override the
PID loop to scale the output as follows.
If the input variable equals the User Control setpoint, the output will be
determined by the PID loop. In this situation the override has no effect on the
output value.
If the input variable is above the User Control setpoint, the output could increase
from 0% to 100% as the input variable increases from the User Control setpoint