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Safety controls include the following:
•
High-pressure switch located in the refrigerant discharge
line and wired across the HPC terminals on the UPM.
•
Low-pressure switch located in the unit refrigerant suction
line and wired across terminal s LPC1 and LPC2 on the
UPM board.
•
UPM board dry contacts are normally open (NO).
•
Water-side freeze protection sensor, mounted close to con-
densing water coil, monitors refrigerant temperature be-
tween condensing water coil and thermal expansion valve.
If temperature drops below or remains at freeze limit trip
for 30 seconds, the controller will shut down the compres-
sor and enter a soft lockout condition. The default freeze
limit trip is 30°F, however this can be changed to 15°F by
cutting the R30 or Freeze1 resistor located on top of DIP
switch SW1. Refer to Fig. 20, Item 3 for resistor location.
If unit is employing a fresh water system (no anti-freeze
protection), it is extremely important to have the Freeze1
R30 resistor set to 30°F in order to shut down the unit at
the appropriate leaving water temperature and protect heat
pump from freezing if a freeze sensor is included.
•
Evaporator freeze protection sensor, mounted between the
thermal expansion device and the evaporator, monitors re-
frigerant temperature between the evaporator coil and ther-
mal expansion valve. If temperature drops below or re-
mains at freeze limit trip for 30 seconds, the controller will
shut down the compressor and enter into a soft lockout
condition. The default freeze limit trip is 30°F. (See Fig. 29
and 30.)
•
The condensate overflow protection sensor is located in
the drain pan of the unit and connected to the 'COND' ter-
minal on the UPM board.
Fig. 29 — Water-Side Freeze Protection Sensor
Fig. 30 — No 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 cy-
cling.
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 does 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 29.
Table 29 — UPM Board Fault Blink Codes
LED
FAULT
BLINKS
0
None
1
High Pressure
2
Low Pressure
Water Coil Freeze
3
Condition
4
Condensate Overflow
5
Brown Out
Air Coil Freeze
6
Condition
46
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
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