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Geothermal Comfort Systems
Carrier Indoor & Outdoor Split Geothermal Heat Pumps - Rev.: 08/10/05
41
CXM Controls
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 fl ashing 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 satisfi ed,
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 viewed by going into test mode.
Note: FP1/FP2 faults are factory set at only one try.
Lockout: In lockout mode, the status LED will begin fast
fl ashing. 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 fl ashes, 10 sec pause, 2 quick fl ashes,
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 60 seconds of a compressor run cycle.
Low pressure lockout code = 3
Water coil low temperature (FP1): The FP1 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
FP1 fault. The FP1 input is bypassed for the initial 60
seconds of a compressor run cycle. FP1 is set at the
factory for one try. Therefore, the control will go into
lockout mode once the FP1 fault has occurred.
FP1 lockout code = 4
Air coil low temperature (FP2): The FP2 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
FP2 fault. The FP2 input is bypassed for the initial 60
seconds of a compressor run cycle. FP2 is set at the
factory for one try. Therefore, the control will go into
lockout mode once the FP2 fault has occurred.
FP2 lockout code = 5
Condensate overfl ow: The condensate overfl ow sensor
must sense overfl ow level for 30 continuous seconds to
be recognized as a CO fault. Condensate overfl ow 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 19VAC to 30VAC. 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
ineffi ciently. A UPS condition exists when:
a) In heating mode with compressor energized, FP2
is greater than 125°F [52°C] for 30 continuous
seconds, or:
b) In cooling mode with compressor energized, FP1
is greater than 125°F [52°C] for 30 continuous
seconds, or:
c) In cooling mode with compressor energized, FP2 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,
the alarm relay will cycle on and off. The cycle rate
will be “on” for 5 seconds, “off” for 25 seconds, “on”
for 5 seconds, “off” for 25 seconds, etc.
UPS warning code = 8
Swapped FP1/FP2 thermistors: During test mode, the
control monitors to see if the FP1 and FP2 thermistors
are in the appropriate places. If the control is in test
mode, the control will lockout, with code 9, after 30
seconds if:
a) The compressor is on in the cooling mode and the
FP1 sensor is colder than the FP2 sensor, or:
b) The compressor is on in the heating mode and the
FP2 sensor is colder than the FP1 sensor.
Swapped FP1/FP2 thermistor code = 9.