System Diagnostic Module
4HP16LT units contain a diagnostic module for trouble- shooting heat pump system failures. By monitoring and analyzing data from the compressor and thermostat demand, the module can accurately detect the cause of electrical and system related failure without any sensors. If a system problem occurs, a flashing LED indicator communicates the failure code.
LED Description
POWER LED (Green) indicates voltage is present at the power connection of the module.
ALERT LED (Yellow) communicates an abnormal system condition through a unique flash code. The ALERT LED will flash a number of times consecutively, pause, and then repeat the process. The number of consecutive
flashes correlates to a particular abnormal condition. TRIP LED (Red) indicates there is a demand signal from the thermostat but no current to the compressor is de- tected by the module. The TRIP LED typically indicates the compressor protector is open or may indicate missing supply power to the compressor.
Interpreting the Diagnostic LEDs
When an abnormal system condition occurs, the diagnos- tic module displays the appropriate ALERT and/or TRIP LED. The yellow ALERT LED will flash a number of times consecutively, pause, and then repeat the process. To identify a flash code number, count the number of con- secutive flashes. Refer to Table 10 below and Table 11 on page 20 for information on the flash codes.
Every time the module powers up, the last ALERT LED flash code that occurred prior to shutdown is displayed for
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| Flash Codes | |
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| LED | Fault Description | Troubleshooting Information |
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| Status |
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| POWER | Module has power | Supply voltage is present at module terminals |
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| (Green) |
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| 1. Compressor protector is open |
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| * Check for high head pressure |
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| Thermostat demand | * Check compressor supply voltage |
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| TRIP | signal Y1 is present, | 2. Outdoor unit power disconnect is open |
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| (Red) | but the compressor | 3. Compressor circuit breaker or fuse(s) is open |
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| is not running | 4. Broken wire or connector is not making contact |
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| 5. Low pressure switch open if present in system |
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| 6. Compressor contactor has failed open |
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| Long Run Time |
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| Compressor is |
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| ALERT | running |
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| (Yellow) | extremely long run |
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| Flash | cycles |
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| Code 1 |
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| (Not applicable on |
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| heat pump models) |
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| 1. High head pressure |
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| * Check high pressure switch if present in system |
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| System | * Check if system is overcharged with refrigerant |
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| ALERT | Pressure Trip | * Check for |
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| Discharge or suction | 2. Condenser coil poor air circulation (dirty, blocked, damaged) |
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| (Yellow) |
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| pressure | 3. Condenser fan is not running |
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| out of limits or | * Check fan capacitor |
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| Code 2 |
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| compressor | * Check fan wiring and connectors |
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| overloaded | * Check fan motor for failure or blockage |
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| 4. Return air duct has substantial leakage |
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| 5. If low pressure switch present in system, check Flash Code 1 info |
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| Table 10 | |
Issue 1004 | Page 22 |