If temperature drops below or remains at the
freeze limit trip for 30 seconds, the controller
will shut the compressor down and enter into
a soft lockout condition. Both the status LED
and the Alarm contact will be active. The
LED will flash (five (5) times) the code
associated with this alarm condition.
Once the UPM detects a brownout condition
its fault LED will flash seven (7) times as
error code indication.
Condensation overflow
The UPM controller continuously monitors
the drain pan for high condensate water
level, and to do so it utilizes a sensor and
identifies an alarm condition when the
sensor’s impedance drops below 230KΩ +/-
15 %. (ONLY when condensate sensor
option is present) Once the UPM senses this
resistance value it enters into a hard lockout
and reports the correspondent code via its
status LED (6 flashes).
Figure 4 - Freeze sensor location
To exit the hard lockout water has to return
to its normal level and UPM has to be reset
by removing the power from the Y terminal
(R if set on the DIP switch) the compressors
will be turned on after anti short cycle
expires.
Brownout protection
The UPM controller will constantly monitor
the power supply, if the nominal voltage
drops below 25% of its value. (18 VAC
approximately), the unit will enter brownout
protection mode. The compressor CC
outputs will be de-energized and the unit will
enter the soft lockout mode.
Sequence of Operation
The UPM sequence of operation illustrated
in the flow chart applies for both refrigerant
circuits. The second compressor is
energized 10 seconds after the first if both
Y1 and Y2 signals are applied at the
simultaneously.
The controller will not monitor the power
supply during the first 500 milliseconds of
compressor start up to avoid noise and false
alarms.
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