Heat Siphon
Heat Siphon Pool Heaters Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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CMP
Display shows “CMP” or compressor error; unit will not heat.
Compressor Start/Run Fault
d1
Display shows “d1” and unit will not start heating.
Defrost Sensor / Circuit Error
dEF
Display shows “dEF” or “DEFROST”; unit pauses heating and fan may stop while compressor continues intermittently.
Defrost Mode Active
EE
Display shows “EE” or “E.E.” and the unit is completely locked out.
General Control Board Error / EEPROM Fault
FAn
Display shows “FAn” or fan error; compressor may not start.
Fan Motor / Fan Feedback Fault
FLO
Display shows “FLO” or “FL” and the unit will not start the compressor; fan may run briefly or not at all.
Insufficient Water Flow / Flow Switch Open
FS
Display shows “FS” or “FS ERR”; unit will not heat or cycles off prematurely.
Water Flow Switch Circuit Fault
HI
Display shows “HI” and the unit will not run; water is already warm or hot.
High Water Temperature Lockout
HP
Unit powers on but quickly shuts down with “HP” on the display; pool water is not heating and the compressor does not stay running.
High Pressure Refrigerant Lockout
HPS
Display shows “HPS”; unit starts then quickly shuts down.
High Pressure Switch Open
LO
Display shows “LO” and the unit will not start or shuts down shortly after starting.
Low Line Voltage / Power Supply Fault
LOt
Display shows “LOt” or “LO TEMP”; unit will not start or shuts down quickly in cold weather.
Low Ambient Temperature Lockout
LP
Display shows “LP” and the unit will not heat; compressor attempts to start but shuts down shortly after.
Low Pressure Refrigerant Lockout
LPS
Display shows “LPS”; unit will not stay running.
Low Pressure Switch Open
OF
Display shows “OF” or “OFF” and unit will not respond to heat commands.
Unit in Off/Standby or External Control Lockout
P1
Display shows “P1”; unit may not start or may run in a limited mode.
Water Temperature Sensor 1 Fault / Calibration Error
P2
Display shows “P2”; unit may shut down or show unstable temperature readings.
Secondary Temperature Sensor / Coil Sensor Fault
rE
Display shows “rE” or “RE”; unit may not follow set temperature correctly.
Remote Thermostat / External Control Error
SEn
Display shows “SEn” or “SEN ERR”; unit will not run or cycles erratically.
Temperature Sensor Fault (Water or Air)
tH
Display shows “tH” or thermal error; unit shuts down unexpectedly.
Thermal Overload / High Internal Temperature
Symptom
Automation system calls for heat but the Heat Siphon does not start.
Communication / Control Signal Issue with Pool Automation
Symptom
Condensation drains poorly; water pools inside the base of the unit.
Blocked Condensate Drainage
Symptom
Display is on but unresponsive; buttons do not change settings or start the unit.
Keypad / User Interface Failure
Symptom
Display shows incorrect water temperature compared to a pool thermometer.
Water Temperature Sensing Error / Miscalibration
Symptom
Ice buildup on the evaporator coil or around the top of the unit during operation.
Excessive Coil Icing / Defrost Problem
Symptom
Loud grinding or squealing noise from the top of the unit while running.
Fan Motor Bearing Failure / Fan Blade Damage
Symptom
Rattling or vibrating noise from the cabinet during operation.
Cabinet Vibration / Loose Panels
Symptom
Strong chemical or metallic smell around the unit when running.
Corrosion or Chemical Off‑Gassing
Symptom
Unit frequently trips the circuit breaker when starting or during operation.
Overcurrent / Short Circuit
Symptom
Unit leaks water from the base or around the plumbing connections.
Water Leak from Heat Exchanger or Plumbing
Symptom
Unit operates but causes noticeable humming or buzzing in nearby electrical equipment.
Electrical Noise / Interference
Symptom
Unit powers on but compressor never starts; only the fan runs continuously.
Compressor Not Starting
Symptom
Unit runs (fan and compressor on) but pool water does not heat or heats very slowly.
Reduced Heating Capacity / Inefficient Heat Transfer
Symptom
Unit short‑cycles: starts and stops frequently without reaching set temperature.
Short Cycling / Improper Control Logic
Symptom
Unit will not start at all; display is blank and no lights or sounds are present.
No Power / Dead Unit
Symptom
Water flow through the heater seems restricted; high filter pressure when heater is in line.
Hydraulic Restriction Through Heat Exchanger
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| CMP |
Display shows “CMP” or compressor error; unit will not heat.
|
Compressor Start/Run Fault | View Details |
| d1 |
Display shows “d1” and unit will not start heating.
|
Defrost Sensor / Circuit Error | View Details |
| dEF |
Display shows “dEF” or “DEFROST”; unit pauses heating and fan may stop while compressor continues intermittently.
|
Defrost Mode Active | View Details |
| EE |
Display shows “EE” or “E.E.” and the unit is completely locked out.
|
General Control Board Error / EEPROM Fault | View Details |
| FAn |
Display shows “FAn” or fan error; compressor may not start.
|
Fan Motor / Fan Feedback Fault | View Details |
| FLO |
Display shows “FLO” or “FL” and the unit will not start the compressor; fan may run briefly or not at all.
|
Insufficient Water Flow / Flow Switch Open | View Details |
| FS |
Display shows “FS” or “FS ERR”; unit will not heat or cycles off prematurely.
|
Water Flow Switch Circuit Fault | View Details |
| HI |
Display shows “HI” and the unit will not run; water is already warm or hot.
|
High Water Temperature Lockout | View Details |
| HP |
Unit powers on but quickly shuts down with “HP” on the display; pool water is not heating and the compressor does not stay running.
|
High Pressure Refrigerant Lockout | View Details |
| HPS |
Display shows “HPS”; unit starts then quickly shuts down.
|
High Pressure Switch Open | View Details |
| LO |
Display shows “LO” and the unit will not start or shuts down shortly after starting.
|
Low Line Voltage / Power Supply Fault | View Details |
| LOt |
Display shows “LOt” or “LO TEMP”; unit will not start or shuts down quickly in cold weather.
|
Low Ambient Temperature Lockout | View Details |
| LP |
Display shows “LP” and the unit will not heat; compressor attempts to start but shuts down shortly after.
|
Low Pressure Refrigerant Lockout | View Details |
| LPS |
Display shows “LPS”; unit will not stay running.
|
Low Pressure Switch Open | View Details |
| OF |
Display shows “OF” or “OFF” and unit will not respond to heat commands.
|
Unit in Off/Standby or External Control Lockout | View Details |
| P1 |
Display shows “P1”; unit may not start or may run in a limited mode.
|
Water Temperature Sensor 1 Fault / Calibration Error | View Details |
| P2 |
Display shows “P2”; unit may shut down or show unstable temperature readings.
|
Secondary Temperature Sensor / Coil Sensor Fault | View Details |
| rE |
Display shows “rE” or “RE”; unit may not follow set temperature correctly.
|
Remote Thermostat / External Control Error | View Details |
| SEn |
Display shows “SEn” or “SEN ERR”; unit will not run or cycles erratically.
|
Temperature Sensor Fault (Water or Air) | View Details |
| tH |
Display shows “tH” or thermal error; unit shuts down unexpectedly.
|
Thermal Overload / High Internal Temperature | View Details |
| – |
Automation system calls for heat but the Heat Siphon does not start.
|
Communication / Control Signal Issue with Pool Automation | View Details |
| – |
Condensation drains poorly; water pools inside the base of the unit.
|
Blocked Condensate Drainage | View Details |
| – |
Display is on but unresponsive; buttons do not change settings or start the unit.
|
Keypad / User Interface Failure | View Details |
| – |
Display shows incorrect water temperature compared to a pool thermometer.
|
Water Temperature Sensing Error / Miscalibration | View Details |
| – |
Ice buildup on the evaporator coil or around the top of the unit during operation.
|
Excessive Coil Icing / Defrost Problem | View Details |
| – |
Loud grinding or squealing noise from the top of the unit while running.
|
Fan Motor Bearing Failure / Fan Blade Damage | View Details |
| – |
Rattling or vibrating noise from the cabinet during operation.
|
Cabinet Vibration / Loose Panels | View Details |
| – |
Strong chemical or metallic smell around the unit when running.
|
Corrosion or Chemical Off‑Gassing | View Details |
| – |
Unit frequently trips the circuit breaker when starting or during operation.
|
Overcurrent / Short Circuit | View Details |
| – |
Unit leaks water from the base or around the plumbing connections.
|
Water Leak from Heat Exchanger or Plumbing | View Details |
| – |
Unit operates but causes noticeable humming or buzzing in nearby electrical equipment.
|
Electrical Noise / Interference | View Details |
| – |
Unit powers on but compressor never starts; only the fan runs continuously.
|
Compressor Not Starting | View Details |
| – |
Unit runs (fan and compressor on) but pool water does not heat or heats very slowly.
|
Reduced Heating Capacity / Inefficient Heat Transfer | View Details |
| – |
Unit short‑cycles: starts and stops frequently without reaching set temperature.
|
Short Cycling / Improper Control Logic | View Details |
| – |
Unit will not start at all; display is blank and no lights or sounds are present.
|
No Power / Dead Unit | View Details |
| – |
Water flow through the heater seems restricted; high filter pressure when heater is in line.
|
Hydraulic Restriction Through Heat Exchanger | View Details |
No matching codes found
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