Carrier Omnizone 50BVC Installation, Start-Up, Service And Controls Operation And Troubleshooting page 35

Fig. 25 — Dip Switch Settings
The following table is available on the UPM board as well and it
depicts the switch position and its associated functionality
(Table 16 ).
Table 16 — UPM Dip Switch Configuration
4 LOCKOUT
3 RESET
2 ALARM
1 TEST
Selectable Alarm Mode
The UPM controller can be configured to have either a constant
signal or a pulse.
If constant (CONT) is selected the UPM will provide a closed
contact until the alarm is cleared.
If pulsed (PULSE) is selected the UPM will sequence the alarm
contact with the fault LED flashes.
Freeze Protection
The default setting for the freeze limit trip is 30°F; this can be
changed to 15°F by cutting the R17 for Compressor 1 and R77 for
Compressor 2 resistor located on top of the DIP switch SW1. The
UPM controller will constantly monitor the refrigerant tempera-
ture with the sensor mounted close to the condensing water coil
between the thermal expansion valve and water coil as shown in
Fig. 26.
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 5 times the code associ-
ated with this alarm condition.
Fig. 26 — Freeze Sensor Location
Brownout Protection
The UPM controller will constantly monitor the power supply. If
the nominal voltage drops below 25% of its value (18 VAC ap-
proximately), the unit will enter brownout protection mode. The
compressor CC outputs will be de-energized and the unit will en-
ter the soft lockout mode. The controller will not monitor the
power supply during the first 500 milliseconds of compressor
start-up to avoid noise and false alarms. Once the UPM detects a
LOCKOUT
RESET
ALARM
TEST
4 2
R Y
CONT PULSE
YES NO
FREEZE SENSOR
brownout condition, its fault LED will flash 7 times as error code
indication.
Condensation Overflow
The UPM controller continuously monitors the drain pan for high
condensate water level. To do so it utilizes a sensor which, when
condensate sensor option is present, identifies an alarm condition
when the sensor's impedance drops below 230,000 ± 15%. Once
the UPM senses this resistance value, it enters into a hard lockout
and reports the corresponding code via its status LED (6 flashes).
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 af-
ter anti-short cycle expires.
Sequence of Operation,
CV Units — 50BVC,Q,T,V
The following sequence of operation applies to constant volume
units.
Cooling is initiated when the set point in the remote thermostat is
not met (space temperature is higher than set point). The unit se-
quence of operation is as follows:
Contact closure at the 'G' terminal will provide power to the sup-
ply fan contactor energizing the supply fan. The supply fan will be
off during unoccupied schedule, depending upon the features of
the thermostat used.
The 'O' terminal energizes the reversing valve (heat pump units
only). Typically 'Y1' will also be energized at this time for cool-
ing operation. The second stage of cooling 'Y2' will be initialized
after a minimum run time and there is a differential from set point
plus a deadband or a proportional plus integral calculation based
upon demand and length of time space temperature is greater than
set point.
Additional assurance is provided by a delay on make timer in the
second-stage compressor contactor circuit to avoid dual compres-
sor in-rush starting current.
Heating mode (heat pump models only) follows the same se-
quence as above except that the reversing valve is not energized.
The UPM sequence of operation illustrated in Fig. 27 applies for
both refrigerant circuits. The second compressor is energized 10
seconds after the first if both Y1 and Y2 signals are applied
simultaneously.
WATER ECONOMIZER COOLING
The unit diverts condenser inlet waterflow through an optional
economizer coil to pre-cool evaporator entering airflow. If the en-
tering water temperature is colder than the setting on the aquastat
and the return-air temperature is warmer than the setting on the re-
turn air thermostat, the two-position diverting valve will direct wa-
ter to the economizer coil.
Economizer water flow is in series with the condensers allowing
compressor operation while the economizer is operating.
Y CALL (COOLING OR HEATING)
The UPM will energize the compressor's output (CC) in an event
of a "Y" Call from a thermostat or controller (after the random
start-up and/or the anti-short cycle delays have elapsed). The Y in-
put terminal must be energized with a 24 VAC signal.
35