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Modes of Operation (Cont.)
C
Remote Setpoint Controller With Local Adjustment
When the UCM-420A is used as a remote setpoint controller with local adjustment, a 4-20 mA, 1-5 VDC, or time-
based pulse-width signal from a BAS controller sends a setpoint signal to the UCM-420A. The setpoint poten-
tiometer on the UCM-420A or a UCM-SPA setpoint potentiometer wired to the "Local Setpoint" terminals may then
be used to adjust the setpoint ±12.5% of the input range, or a PreCon "XA" Setpoint Option on a temperature
sensor may be used as a local setpoint and may adjust the setpoint ±9.4% of the input range. (A 4-20 mA or 1-5 VDC
signal may also be used as the "Local Setpoint" signal, although these are normally remote setpoint signals. When
these are used as local setpoints in this mode, they have the authority to adjust the setpoint ±12.5% of the input
range.) A 4-20 mA, 1-5 VDC, or thermistor input (with a range of 50 to 90°F)* from the process being controlled
allows the UCM-420A to monitor the system and provide a proportional/integral, direct- or reverse-acting signal to
the device being controlled. See page 18 for instructions on operating the UCM-420A in this mode.
EXAMPLE: REMOTE SETPOINT CONTROLLER WITH LOCAL ADJUSTMENT - VAV Control
In this example, a PreCon ST-S3E-XA Thermistor with setpoint adjustment is located in the space being con-
trolled. The setpoint is a 4-20 mA signal from a BAS controller. The PreCon "XA" setpoint adjuster will have
authority to adjust the setpoint ±3.76°F. [(90 to 50°F*) x 0.094 = 3.76°F] In this example, the BAS controller could
be programmed to send a setpoint signal for 72°F (12.8 mA) during the day, 82°F (16.8 mA) at night, etc.
BAS
CONTROLLER
SUPPLY
AIR
TERMINAL
4-20 MA REMOTE
SETPOINT SIGNAL
4-20 MA P/I
CONTROL
SIGNAL
ACT.
VAV
THERMISTOR
TEMP INPUT
UCM-420A
LOCAL SETPOINT
ADJUST
SUPPLY
AIR
10
* Other ranges available
ST-S3E-XA
TEMPERATURE SENSOR
WITH SETPOINT ADJUST
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