Installation, Operation & Maintenance - HNW Series
Safety Features – CXM Control
The safety features below are provided to protect
the compressor, heat exchangers, wiring and other
components from damage caused by operation outside
of design conditions.
Anti-short cycle protection: The control features a 5
minute anti-short cycle protection for the compressor.
Note: The 5 minute anti-short cycle also occurs at power up.
Random start: The control features a random start upon
power up of 5-80 seconds.
Fault Retry: In Fault Retry mode, the Status LED begins
slowly flashing to signal that the control is trying to
recover from a fault input. The control will stage off the
outputs and then “try again” to satisfy the thermostat
input call. Once the thermostat input call is satisfied,
the control will continue on as if no fault occurred. If 3
consecutive faults occur without satisfying the thermostat
input call, the control will go into “lockout” mode. The last
fault causing the lockout will be stored in memory and
can be by going into test mode. Note: LT1/LT2 faults are
factory set at only one try.
Lockout: In lockout mode, the status LED will begin fast
flashing. The compressor relay is turned off immediately.
Lockout mode can be “soft” reset by turning off the
thermostat (or satisfying the call). A “soft” reset keeps
the fault in memory but resets the control. A “hard” reset
(disconnecting power to the control) resets the control
and erases fault memory.
Lockout with emergency heat: While in lockout mode,
if W becomes active (CXM), emergency heat mode will
occur.
High pressure switch: When the high pressure switch opens
due to high refrigerant pressures, the compressor relay is
de-energized immediately since the high pressure switch
is in series with the compressor contactor coil. The high
pressure fault recognition is immediate (does not delay for 30
continuous seconds before de-energizing the compressor).
High pressure lockout code = 2
Example: 2 quick flashes, 10 sec pause, 2 quick flashes,
10 sec. pause, etc.
Low pressure switch: The low pressure switch must be open
and remain open for 30 continuous seconds during “on”
cycle to be recognized as a low pressure fault. If the low
pressure switch is open for 30 seconds prior to compressor
power up it will be considered a low pressure (loss of
charge) fault. The low pressure switch input is bypassed for
the initial 120 seconds of a compressor run cycle.
Low pressure lockout code = 3
Source Water coil low temperature (LT1): The LT1
thermistor temperature must be below the selected
low temperature limit setting for 30 continuous
seconds during a compressor run cycle to be
recognized as a LT1 fault. The LT1 input is bypassed
for the initial 120 seconds of a compressor run cycle.
LT1 is set at the factory for one try. Therefore, the
control will go into lockout mode once the LT1 fault
has occurred.
LT1 lockout code = 4
Load Water coil low temperature (LT2): The LT2
thermistor temperature must be below the selected
low temperature limit setting for 30 continuous
seconds during a compressor run cycle to be
recognized as a LT2 fault. The LT2 input is bypassed
for the initial 120 seconds of a compressor run cycle.
LT2 is set at the factory for one try. Therefore, the
control will go into lockout mode once the LT2 fault
has occurred.
LT2 lockout code = 5
Condensate overflow: The condensate overflow sensor
must sense overflow level for 30 continuous seconds
to be recognized as a CO fault. Condensate overflow
will be monitored at all times.
CO lockout code = 6
Over/under voltage shutdown: An over/under voltage
condition exists when the control voltage is outside the
range of 18VAC to 31.5VAC. Over/under voltage shut
down is a self-resetting safety. If the voltage comes
back within range for at least 0.5 seconds, normal
operation is restored. This is not considered a fault or
lockout. If the CXM is in over/under voltage shutdown
for 15 minutes, the alarm relay will close.
Over/under voltage shut down code = 7
Unit Performance Sentinel-UPS (patent pending):
The UPS feature indicates when the heat pump is
operating inefficiently. A UPS condition exists when:
a) In heating mode with compressor energized, LT2
is greater than 125°F [52°C] for 30 continuous
seconds, or:
b) In cooling mode with compressor energized, LT1
is greater than 125°F [52°C] for 30 continuous
seconds, or:
c) In cooling mode with compressor energized, LT2 is
less than 40°F [4.5°C] for 30 continuous seconds.
If a UPS condition occurs, the control will immediately
go to UPS warning. The status LED will remain on as if
the control is in normal mode. Outputs of the control,
excluding LED and alarm relay, will NOT be affected
by UPS. The UPS condition cannot occur during a
compressor off cycle. During UPS warning,
Safety Features - CXM Controls
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