WaterFurnace Fault Codes Troubleshooting Guide and Error Code Chart

WaterFurnace geothermal heat pump owners and technicians rely on fault codes to identify issues quickly and minimize downtime. This guide explains common WaterFurnace fault codes, possible causes, and practical troubleshooting steps to resolve them safely. Follow manufacturer recommendations and disconnect power before servicing electrical components.

Code	Typical Meaning	Immediate Action
E01	Supply/Return Temperature Fault	Check sensor and fluid flow
CF1	Compressor Fault 1 (Overcurrent/Lockout)	Inspect compressor, wiring, and contactor
E06	Low Refrigerant Or Freeze Condition	Check system pressure and coils
F28	High Discharge Temperature	Verify airflow, water flow, and transducer

How WaterFurnace Fault Codes Work

WaterFurnace units use a controller to monitor sensors and components and display alphanumeric fault codes when parameters exceed set thresholds. Codes vary by model and controller generation, but they generally indicate sensor failures, flow problems, electrical issues, refrigeration faults, or communications errors. Interpreting the code narrows down the likely subsystem to inspect.

Accessing And Reading Fault Codes

Most WaterFurnace systems display fault codes on the unit’s thermostatic interface or on the system controller. Some models support remote monitoring or building management integration. When a fault appears, record the code, status (active or historical), and any additional diagnostics shown by the controller. Documenting runtime and ambient conditions helps diagnose intermittent faults.

General Troubleshooting Workflow

Technicians should follow a structured approach: verify the fault, check safety and power, inspect sensors and wiring, evaluate fluid and airflow, and then test refrigeration or electrical components. This reduces misdiagnosis and unnecessary parts replacement. Always isolate power before opening panels and follow lockout-tagout procedures.

Common Fault Codes And Detailed Causes

E01 / Supply Or Return Temperature Sensor Fault

E01 typically points to an open or shorted sensor for supply or return water temperature. Symptoms include incorrect temperature reads and improper system cycling. Technicians should measure sensor resistance and compare to the manufacturer’s table, inspect wiring and connectors for corrosion, and verify probe placement and immersion depth. Replacing a failed sensor often resolves the issue.

E02 / Air Temperature Or Coil Sensor Fault

E02 indicates a fault with air or evaporator coil sensors. Causes include damaged probes, loose wiring, or sensor contamination. Verify sensor continuity, clean coils if covered in debris, and ensure sensors are secured in correct locations. If the sensor passes resistance checks, examine the controller input and harness for voltage or grounding problems.

CF1 / Compressor Fault 1 (Lockout Or Overcurrent)

CF1 signals compressor protection tripping due to high current, locked rotor, or repeated start failures. Check compressor amperage with a clamp meter and compare to nameplate values. Inspect contactors, supply voltage quality, run capacitors, and motor winding continuity. Look for refrigerant issues that cause overloading, such as liquid floodback or high head pressure. Replace or repair defective components and clear the fault after resolving root causes.

E06 / Low Refrigerant Or Freeze Detection

E06 often points to low refrigerant charge leading to low suction pressure or coil freezing. Verify system pressures with gauges, inspect for oil traces indicating leaks, and perform leak detection (electronic detector or bubble test). Confirm proper water/glycol flow and check TXV or expansion device operation. Recharging the system should only occur after repairs are made and a thorough evacuation is completed.

F28 / High Discharge Temperature

F28 indicates the compressor discharge or refrigerant discharge temperature exceeded safe limits. Contributing issues include low refrigerant, restricted airflow, poor water flow through the condenser, faulty discharge thermistor, or excessive ambient conditions. Measure discharge temperature and evaluate condenser water/glycol temperatures and flow rates. Restore proper flow and airflow and verify sensor accuracy.

E13 / Water Flow Or Pump Fault

E13 indicates inadequate water/glycol flow or a pump failure. Confirm pump operation, motor amps, and impeller integrity. Measure flow rate and pressure differential across the coil. Check for airlocks, closed valves, blocked strainers, or frozen loops. In closed-loop geothermal systems, verify loop pump speed and loop antifreeze concentration to ensure proper viscosity and heat transfer.

Comms Errors / Communication Faults

Communication faults occur between the system controller and thermostat or BMS. Causes include loose connectors, incorrect baud settings, or failed controller modules. Verify wiring topology, termination resistors, and network addressing. Reboot devices and update firmware if available. Replace defective modules if communication remains unstable.

Diagnostic Tools And Tests

Effective diagnosis uses multimeters, clamp meters, refrigerant gauges, temperature probes, pressure transducers, and leak detectors. Advanced technicians may use data logging to capture transient events. Record baseline readings after repairs to verify normal operation.

Safety And Best Practices

Always de-energize the unit before accessing electrical components. Use personal protective equipment and follow refrigerant handling regulations (EPA Section 608 in the U.S.). Verify proper ventilation when working with refrigerants and ensure recovered refrigerant is stored per environmental rules. Document all repairs and update system logs for future reference.

Preventive Maintenance To Reduce Faults

Regular preventive maintenance reduces fault frequency. Recommended tasks include cleaning coils and strainers, verifying fluid levels and antifreeze concentration, checking electrical connections and contactors, testing sensors, and confirming pump operation. Schedule seasonal inspections and log readings to spot trends prior to failures.

When To Call A Licensed Technician

Manufacturer warranties and refrigerant regulations typically require licensed HVAC technicians for certain repairs. Call a licensed technician when faults involve refrigerant recharge, compressor replacement, complex electrical diagnostics, or when the fault persists after basic troubleshooting. A licensed pro will have specialized tools and access to OEM parts and firmware updates.

Mapping Fault Codes To Actions

Fault Category	Likely Cause	Immediate Checks
Sensor Faults	Open/short sensors, wiring issues	Measure resistance, inspect wiring/connectors
Flow Faults	Pumps, valves, blockages, airlocks	Verify pump run, flow rate, valve positions
Refrigeration Faults	Low charge, TXV issues, compressor stress	Check pressures, temps, compressor amps
Electrical/Compressor	Contactor, capacitor, motor winding issues	Measure voltage, current, inspect contactor
Communications	Wiring, controller, BMS config	Check bus wiring, terminate, reboot controllers

Model-Specific Considerations

WaterFurnace product families (e.g., Envision, 7 Series, 5 Series) use different controllers and code sets. Always consult the unit’s service manual and code index when troubleshooting. OEM documentation lists fault code definitions, threshold values, and step-by-step diagnostic flows specific to the model. Using model-specific procedures reduces diagnostic time.

Sample Troubleshooting Scenarios

Scenario: Unit Displays E01 After Startup

If E01 appears immediately after startup, suspect sensor wiring or a disconnected probe. Inspect the harness at the control board, measure sensor resistance at the controller terminals, and check for recent service that might have left a connector loose. If the sensor is faulty, replace and clear the code.

Scenario: CF1 Tripping Repeatedly During High Load

Repeated CF1 events under high load suggest compressor overheating or overcurrent. Check for low refrigerant, high head pressure, or restricted condenser water flow. Measure compressor amps during operation. If electrical supply is within tolerance and flow is adequate, consult the compressor manufacturer specifications for further tests.

Scenario: Intermittent Comms Fault With BMS

Intermittent comms faults often stem from grounding loops, incorrect wiring topology, or noise on the data line. Verify twisted-pair cabling, proper termination, and robust ground references. Replacing aged communication cables and checking surge protection can restore stable communications.

Clearing Fault Codes And Verifying Repair

After resolving the root cause, clear stored fault codes via the controller interface and restart the unit under monitored conditions. Verify that the code does not reoccur and log post-repair operating temperatures, pressures, and currents. A 24–72 hour observation period is useful for intermittent problems.

Resources And References

For accurate diagnostics, technicians should reference the WaterFurnace service manual for the specific model and controller firmware release. Manufacturer technical support and authorized distributors can provide wiring diagrams, software updates, and replacement part numbers. Trade associations and EPA resources provide guidance on refrigerant handling and certification requirements.

Key Takeaways

• Fault codes pinpoint subsystems—use them to focus inspections.
• Follow a structured diagnostic workflow to avoid unnecessary replacements.
• Maintain preventive care to minimize future faults.
• Engage licensed technicians for refrigerant and major electrical repairs.

For exact code definitions and step-by-step diagnostics, consult the unit-specific WaterFurnace service manual or contact an authorized service provider. Proper documentation and adherence to safety protocols ensure reliable operation and long system life.