Heat Controller DXM2 Application And Instruction Manual page 8

Application, Operation, & Maintenance Manual
DXM2 Controls
SAFETY FEATURES
The following safety features 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 5-80 second
random start upon power up. The random start delay will
be present after a control power up and after returning from
Night Setback or Emergency Shutdown modes.
Extended Compressor Operation Monitoring - If the
compressor relay has been on for 4 continuous hours, then
the control will automatically turn off the compressor relay
and wait the short cycle protection time. All appropriate
safeties will be monitored during the off time. If all operation
is normal, and if the compressor demand is still present,
the control will turn the compressor back on.
Fault Retry - In Fault Retry Mode, the Fault LED begins
slow fl ashing to signal that the control is trying to recover
from a fault input. The DXM2 Control will stage off the
outputs and then "try again" to satisfy the thermostat call for
compressor. Once the thermostat input calls are satisfi ed,
the control will continue on as if no fault occurred. If 3
consecutive faults occur without satisfying the thermostat
call for compressor, then the control will go to Lockout
Mode. The last fault causing the lockout will be stored in
memory and is displayed at the Fault LED by entering the
Test mode.
Note: LT1 and LT2 faults are factory set for one try, so
there will be no "retries" for LT1 and LT2 faults. The
control will only try one time for these faults.
FAULT CODES
Lockout - In Lockout Mode, the Fault LED will begin fast
fl ashing. The compressor relay is turned off immediately.
The fan output will be turned off after the current blower off
delay unless auxiliary heat is active. The Lockout Mode
can be "soft" reset via the thermostat by removing the call
for compressor, or by a "hard" reset (disconnecting power
to the control). The fault code will be stored in non-volatile
memory that can be displayed by the Fault LED by entering
the Test mode, even if power was removed from the
control.
Lockout with Emergency Heat - If the DXM2 is
confi gured for Heat Pump thermostat Mode (see DIP 1.3),
DXM2 UNIT CONTROLS
CAUTION!
CAUTION! Do not restart units without inspection and
remedy of faulting condition. Equipment damage may occur.
the DXM2 is in Lockout Mode, and the W input becomes
active, then Emergency Heat Mode will occur during
Lockout. For Emergency Heat, the fan and auxiliary heat
outputs will be activated.
Fault Code 2: High Pressure Switch – When the High
Pressure switch opens due to high refrigerant pressures,
the compressor relay is de–energized immediately. The
High Pressure fault recognition is immediate (does not
delay for 30 continuous seconds before de–energizing the
compressor). When the Test mode is activated, the Fault
LED will display a fault code of 2 for a High Pressure fault.
Fault Code 3: Loss of Charge Switch – The Loss of
Charge Switch must be open and remain open for 30
continuous seconds during a compressor "on" cycle to
be recognized as a Loss of Charge fault. If the Loss of
Charge switch is open for 30 seconds prior to compressor
power up it will be considered a Loss of Charge fault. The
Loss of Charge Switch input is bypassed for the initial 120
seconds of a compressor run cycle. When the Test mode
is active, the Fault LED will display a fault code of 3 for a
Loss of Charge fault.
Fault Code 4: Water Coil Low Temperature Cut-Out
Limit (LT1) - The control will recognize an LT1 fault, during
a compressor run cycle if:
a) the LT1 thermistor temperature is below the selected
low temperature protection limit setting for at least 50
seconds, AND
b) the LT1 thermistor temperature is rising (getting
warmer) at a rate LESS than 2°F per 30 second time
period.
The LT1 input is bypassed for the initial 120 seconds of a
compressor run cycle. When the Test mode is active, the
Fault LED will display a fault code of 4 for a LT1 fault.
Fault Code 5: Air Coil Low Temperature Cut-Out
(LT2) - The control will recognize an LT2 fault, during a
compressor run cycle if:
a) the LT2 thermistor temperature is below the low
temperature protection limit setting for at least 50
seconds, AND
b) the LT2 thermistor temperature is rising (getting
warmer) at a rate LESS than 2°F per 30 second time
period.
The LT2 input is bypassed for the initial 120 seconds of a
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Heat Controller, Inc.