D Output Expander (Multiplexed Pwm) - Kele UCM-420A Operating And Installation Instructions

D
Output Expander (Multiplexed PWM)
The UCM-420A may be operated in a multiplexed pulse-width modulation mode so that one BAS output may control
up to eight groups of UCM-420As with each group able to have a different setpoint. When operated in this mode,
each UCM-420A accepts a 4-20 mA, 1-5 VDC, or thermistor input (with a range of 50 to 90°F)* from the process
being controlled. The "PWM INPUT" terminals are wired to the normally open contacts on a BAS controller. The
BAS controller is programmed to send a series of 24 VAC or 24 VDC time-based pulse-width signals to the
UCM-420As. These PWM signals select which units are to be addressed, and adjust their setpoints as required.
The UCM-420As which are not being addressed ignore the new setpoint signal and continue to control based on
their previous setpoint. Each UCM-420A will monitor its input signal and send a P/I control signal to the controlled
device to maintain the required setpoint. When operated in this mode, the local setpoint may also be used to adjust
the setpoint which has been set by the BAS controller. The setpoint potentiometer on the UCM-420A or a UCM-
SPA setpoint potentiometer wired to the "Local Setpoint" terminals may 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.) See page 22 for instructions on
operating the UCM-420A in this mode.
EXAMPLE: UCM-420As USED AS OUTPUT EXPANDERS - Multiplexed VAV Control
In this example, one time-based
pulse-width output from a BAS con-
troller is used to send a setpoint
signal to three UCM-420A setpoint
controllers. Each of these may have
a different setpoint. Each UCM-420A
also accepts an input from a PreCon
Type 3 Temperature Sensor in the
space being controlled. The
UCM-420As send 4-20 mA propor-
tional/integral control signals to the
VAV terminals so that the input
matches the setpoint. Multiple
UCM-420As may be assigned the
same address so that they have the
same setpoint. Eight different
addresses are available so that up to
eight groups of UCM-420As may be
controlled by one BAS output.
Instructions on setting UCM-420A
addresses and how to update the
setpoint with the BAS pulse-width
signal are on page 22.
Modes of Operation (Cont.)
4-20 MA P/I
CONTROL
SIGNAL
SUPPLY
ACT.
AIR
VAV
TERMINAL
SUPPLY
ACT.
AIR
VAV
TERMINAL
SUPPLY
ACT.
AIR
VAV
TERMINAL
11
* Other ranges available
UCM-420A
SUPPLY
AIR
TEMPERATURE
UCM-420A
SUPPLY
AIR
UCM-420A
SUPPLY
AIR
CONTROLLER
+
–
N.O. PWM
CONTACT
ST-S3P
SENSOR
ST-S3P
ST-S3P