8
The UCM-420A is a versatile, low-cost microprocessor-based proportional/integral con-
troller which may be used for a wide variety of control applications.
To select the mode of operation required, please review the descriptions on the following
pages.
EXAMPLE: REMOTE SETPOINT CONTROLLER - Hot Water Reset
In this example, a BAS controller is monitoring outdoor air temperature and sending a time-based pulse-
width signal to the UCM-420A to set the system hot water temperature. By using this control system, the
BAS may also control the hot water temperature based on time of day, minimum space temperature, etc.
The UCM-420A accepts the setpoint signal from the BAS and the input from the hot water temperature
sensor and sends a proportional/integral control signal to the three-way valve to maintain the system hot
water temperature as programmed.
HOT WATER
RESET VALVE
4-20 MA P/I
CONTROL SIGNAL
UCM-420A
HOT WATER SUPPLY
FROM BOILER
PWM REMOTE SETPOINT SIGNAL
4-20 MA TEMPERATURE
INPUT SIGNAL
BAS
CONTROLLER
RTD &
TRANSMITTER
HOT WATER
SUPPLY
TO SYSTEM
HOT WATER
RETURN
FROM SYSTEM
A
Remote Setpoint Controller
When the UCM-420A is used as a remote setpoint controller, 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 UCM-420A monitors a 4-20 mA, 1-5 VDC, or
thermistor input from the process being controlled to provide a proportional/integral control signal to the controlled
device. This signal may be direct- or reverse-acting. See page 13 for instructions on operating the UCM-420A in
this mode.
Modes of Operation
