Carrier Aquazone 50PTH024 Installation, Start-Up And Service Instructions Manual page 55

Fig. 41 — Water-Side Freeze Protection Sensor
Fig. 42 — Air Coil Freeze Protection Sensor
The UPM board includes the following features:
Anti-short Cycle Timer
A 5-minute delay on break timer prevents compressor short
cycling.
Random Start
Each controller has an unique random start delay ranging from
270 to 300 seconds on initial power up to reduce the chance of
multiple units simultaneously starting at the same time after power
up or after a power interruption, thus avoiding creating large in-
rush current.
Low Pressure Bypass Timer
If the compressor is running and the low-pressure switch opens,
the controller will keep the compressor ON for 120 seconds. After
2 minutes, if the low-pressure switch remains open, the controllers
will shut down the compressor and enter a soft lockout. The com-
pressor will not be energized until the low-pressure switch closes
and the anti-short cycle time delay expires. If the low-pressure
switch opens 2 to 4 times in 1 hour, the unit will enter a hard lock-
out. In order to exit hard lockout power to the unit would need to
be reset.
Brownout/Surge/Power Interruption Protection
The brownout protection in the UPM board will shut down the
compressor if the incoming power falls below 18 VAC. The com-
pressor will remain OFF until the voltage is above 18 VAC and
ANTI-SHORT CYCLE TIMER (300 seconds) times out. The unit
will not go into a hard lockout.
Malfunction Output
Alarm output is normally open (NO) dry contact. If pulse is select-
ed the alarm output will be pulsed. The fault output will depend on
the DIP switch setting for ALARM. If it is set to CONST, a con-
stant signal will be produced to indicate a fault has occurred and
the unit requires inspection to determine the type of fault. If it is
set to PULSE, a pulse signal is produced and a fault code is detect-
ed by a remote device indicating the fault. The remote device must
have a malfunction detection capability when the UPM board is
set to PULSE.
LED Fault Indicator
The UPM includes an alarm indicator with blink codes to indicate
a UPM fault. (See Table 24.)
Table 24 — UPM Board Fault Blink Codes
LED
FAULT
BLINKS
0 None
1 High Pressure
2 Low Pressure
Water Coil Freeze
3
Condition
Condensate
4
Overflow
5 Brown Out
Air Coil Freeze
6
Condition
Freeze Protection Sensors 1 and 2 (FP1 and FP2)
FP1 is located on the refrigerant liquid line between the TXV
(thermostatic expansion valve) and the coaxial heat exchanger. If
the temperature of the refrigerant entering the coaxial coil (heating
mode) drops below or remains at 26°F (–6.6°C) for 30 seconds the
UPM controller will shut down the compressor and enter into a
soft lockout condition. Both the status LED and the Alarm contact
will be active. The LED will flash three (3) times for this alarm
condition. If this alarm occurs 2 times (or 4 times if the Lockout
DIP switch is set to 4) within an hour the controller will enter into
a hard lockout condition. The FP1 freeze limit trip can be lowered
to 15°F (–9.4°C) by cutting the R30 sensor located near the top of
DIP switch SW1. However, careful consideration should be given
before cutting resistor R30. For example, if the unit is employing a
fresh water system resistor R30 should remain to protect the coax-
ial heat exchanger from freezing and damaging the unit.
FP2 is located on the refrigerant liquid line between the TXV and
the indoor coil. If the temperature of the refrigerant entering the in-
door coil (cooling mode) drops below or remains at 26°F (–6.6°C)
for 30 seconds the UPM controller will shut down the compressor
and enter into a soft lockout condition. Both the status LED and
the alarm contact will be active. The LED will flash six (6) times
for this alarm condition. If this alarm occurs 2 times (or 4 times if
the LOCKOUT DIP switch is set to 4) within an hour the control-
ler will enter into a hard lockout condition. The FP2 freeze limit
trip can be lowered to 15°F (–9.4°C) by cutting the R24 sensor lo-
cated near the top of DIP switch SW1. However, careful consider-
ation should be given before cutting resistor R24. For example, a
low refrigerant temperature could cause frosting on the indoor
coil, which restricts airflow causing the unit to malfunction.
Intelligent Reset
If a fault condition is initiated, the 5 minute delay on break time
period is initiated and the unit will restart after these delays expire.
During this period the fault LED will indicate the cause of the
fault. If the fault condition still exists or occurs 2 or 4 times (de-
pending on 2 or 4 setting for LOCKOUT DIP switch) before 60
minutes, the unit will go into a hard lockout and requires a manual
lockout reset. A single condensate overflow fault will cause the
unit to go into a hard lockout immediately, and will require a man-
ual lockout reset.
55
FAULT CRITERIA
All fault conditions nominal.
Refrigerant discharge pressure has
exceeded 600 psig.
Refrigerant suction pressure has fallen
below 40 psig.
Refrigerant temperature to the water
coil has fallen below 30°F for 30
seconds.
Condensate levels in the unit drain pan
are too high.
Control voltage has fallen below 18
VAC.
Refrigerant temperature to the air coil
has fallen below 30°F for 30 seconds.