Heat Controller manual DXM2 Controls, DXM2 UNIT CONTROLS, Heat Controller, Inc, Safety Features

Application, Operation, & Maintenance Manual DXM2 UNIT CONTROLS Heat Controller, Inc.

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 flashing 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 satisfied, 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 flashing. 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

configured for Heat Pump thermostat Mode (see DIP 1.3),

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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