Structured geothermal diagnostics
Troubleshoot the Complete Geothermal System
Identify the exact equipment, confirm the operating symptom, collect measurements, review airflow or water flow, test controls, and document each step before replacing components.
A fault code identifies a condition detected by the control. It does not always identify the failed component or root cause.
Geothermal equipment may contain hazardous voltage, pressurized refrigerant, hot or cold fluid, moving components, capacitors, and sharp surfaces. Disconnect power and verify safe conditions before opening equipment or testing internal components.
Diagnose the system logically
Start with the Symptom, Not a Suspected Part
A compressor, board, sensor, pump, motor, thermostat, or valve can appear to be the problem when the actual cause is elsewhere.
Low airflow can create temperature or pressure faults. Low water flow can create freeze or high-pressure conditions. Incorrect thermostat configuration can prevent stages from operating. A blocked drain can stop an otherwise functional unit.
Troubleshooting should move from basic conditions to more complex testing while recording what was observed at each step.
Eight-step diagnostic process
Move from Equipment Identification to Verified Root Cause
The exact procedure depends on the model, fault, controls, and system configuration.
Identify the Equipment
Record the complete brand, model, serial number, voltage, phase, configuration, options, and connected controls.
Define the Exact Symptom
State what the system does, what it does not do, when the problem occurs, and whether it is intermittent.
Review Fault History
Record active and previous faults, lockouts, resets, weather, thermostat calls, and operating conditions.
Confirm Power and Controls
Verify supply voltage, control voltage, thermostat demand, safeties, fuses, disconnects, and control outputs.
Verify Airflow or Water Flow
Inspect filters, blowers, pumps, valves, fluid, piping, ductwork, static pressure, and flow conditions.
Record Operating Measurements
Measure temperatures, pressure drop, flow, airflow, voltage, current, and control signals under stable operation.
Test the Suspected Circuit
Follow the applicable wiring diagram and service procedure to isolate the failed condition.
Verify the Repair
Operate all relevant modes and stages, confirm the original symptom is resolved, and document final measurements.
Before testing components
Gather the Information That Defines the System
Small differences in model numbers can indicate different controls, voltage, capacity, blower, options, wiring, or parts.
Photograph the complete data label, equipment cabinet, electrical section, thermostat, pumps, piping, ductwork, and any visibly damaged components.
Find the Correct ManualNo display or no operation
Trace Power from the Source to the Control Call
Begin with the simplest external conditions before testing internal boards or replacing control components.
Confirm Building Power
Check the service, breaker, disconnect, fuses, emergency switches, and any external control panels.
Verify Equipment Voltage
Qualified personnel should verify the correct supply voltage and phase at the equipment.
Check Control Voltage
Verify the transformer primary, secondary, fuse, common, and thermostat power.
Confirm Thermostat Demand
Verify thermostat configuration, mode, setpoint, wiring, and output terminals.
Review Safety Inputs
Check condensate, flow, pressure, freeze, overflow, door, or other safety circuits used by the model.
Review Controller Status
Record indicator lights, fault history, lockout state, delay, reset requirements, and control outputs.
Water-flow and freeze faults
Confirm Actual Flow Before Condemning a Sensor or Heat Exchanger
Pumps can run without delivering the required flow.
- Confirm pump or flow-center operation
- Verify valve positions
- Check for trapped air
- Inspect strainers and accessible restrictions
- Confirm antifreeze type and concentration
- Record entering and leaving water temperatures
- Measure pressure drop using an approved method
- Determine estimated or measured flow
- Inspect for leaks, low pressure, or fluid loss
- Compare readings with applicable equipment data
- Verify sensor location and wiring
- Check whether the fault occurs in heating, cooling, or both
Airflow and temperature faults
Restricted Airflow Can Create Multiple Misleading Symptoms
Airflow problems can reduce capacity, increase temperature rise, decrease cooling performance, create noise, affect humidity removal, and contribute to pressure or freeze faults.
Condensate and overflow faults
Inspect the Entire Drainage Path and Safety Circuit
A condensate switch can correctly shut down the unit because of a blocked drain, incorrect trap, failed pump, full pan, poor slope, or water entering from another source.
Inspect the Drain Pan
Look for standing water, rust, cracks, debris, biological buildup, poor slope, or overflow.
Inspect the Trap and Drain
Confirm correct trap arrangement, slope, venting, blockage, freezing, termination, and drainage.
Test the Condensate Pump
Verify reservoir condition, float operation, pump output, discharge tubing, check valve, and power.
Test the Overflow Device
Confirm position, wiring, continuity, float movement, and control response using the approved procedure.
Look for Other Moisture Sources
Inspect piping condensation, cabinet sweating, humid air, leaking valves, drain connections, and nearby plumbing.
Electrical and control troubleshooting
Follow the Wiring Diagram and Verify Inputs and Outputs
Qualified personnel should trace the control sequence rather than replacing boards, relays, motors, or sensors based only on appearance.
Supply Voltage
Verify voltage, phase, balance, breaker, disconnect, fuses, terminals, and conditions under load.
Control Voltage
Check transformer input, secondary output, common, control fuse, thermostat power, and connected accessory load.
Thermostat Inputs
Confirm the expected heating, cooling, fan, staging, auxiliary, and reversing-valve signals.
Safety Inputs
Trace pressure, freeze, flow, condensate, temperature, overflow, and other safety circuits used by the equipment.
Control Outputs
Verify output from the controller to contactors, relays, pumps, valves, blowers, heaters, and alarms.
Connected Loads
Test the controlled component, wiring, resistance, current, mechanical condition, and required operating signal.
Heating and cooling performance
Compare Operating Measurements with the Actual System Conditions
Poor heating
Check Capacity, Flow, Airflow, Auxiliary Heat, and Building Load
- Thermostat demand and staging
- Ground-loop entering temperature
- Ground-loop leaving temperature
- Ground-side flow
- Airflow or hydronic flow
- Supply and return temperatures
- Auxiliary-heat operation
- Building load and outdoor conditions
- Distribution-system balance
Poor cooling
Check Heat Rejection, Airflow, Humidity, Condensate, and Controls
- Cooling thermostat call
- Reversing-valve operation
- Ground-loop temperature and flow
- Filter and blower condition
- Total external static pressure
- Return and supply-air temperatures
- Humidity and latent load
- Condensate drainage
- Duct leakage and zoning
Repeated lockouts
Do Not Keep Resetting Without Recording the Conditions
Repeated resets can erase useful fault history, allow a damaging condition to continue, and make intermittent problems harder to diagnose.
- Record the exact fault before resetting
- Record thermostat demand and active stage
- Record outdoor and indoor conditions
- Record ground-side temperatures and flow
- Record air or hydronic temperatures
- Record voltage and current when applicable
- Note how long the unit operated before the fault
- Check whether the fault occurs in one mode only
- Review recent repairs or control changes
- Contact technical support with the complete record
Escalating to technical support
Send a Complete Diagnostic Package
The most useful support request explains the problem and shows what has already been verified.
Include the exact equipment information, fault history, wiring, control sequence, measurements, photographs, replaced parts, and results of each troubleshooting step.
Submit a Technical Support RequestTroubleshooting resources
Continue to the Correct Service Pathway
Manuals and Downloads
Locate model-specific wiring diagrams, installation manuals, service documents, and approved technical information.
Browse technical documents → 02Technical Support
Submit faults, symptoms, measurements, photographs, wiring information, and completed troubleshooting.
Contact technical support → 03Replacement Parts
Request help identifying compatible controls, sensors, motors, pumps, switches, boards, and service components.
Request parts assistance → 04Maintenance and Service
Review filters, pumps, loop fluid, condensate, electrical, controls, hydronics, and service records.
Review maintenance guidance → 05Installation and Commissioning
Review startup measurements, airflow, water flow, controls, electrical, and final documentation.
Review commissioning → 06Find a Dealer or Contractor
Request help locating a qualified local professional for diagnostics, repair, maintenance, or replacement.
Find a local professional →Geothermal troubleshooting FAQs
Common Questions About Diagnosing Geothermal Systems
Final diagnosis depends on the exact equipment, fault, measurements, system configuration, and applicable documentation.
Not always. A fault code usually identifies a condition detected by the control. The root cause may involve airflow, water flow, temperature, pressure, wiring, sensors, controls, pumps, valves, power, or equipment components.
Measurements help determine whether the problem is caused by the suspected component or by the system conditions affecting it.
Possible causes include incorrect staging, low airflow, low water flow, unsuitable loop temperatures, distribution problems, auxiliary-heat issues, control settings, or a building load that exceeds available output.
Yes. Air, closed valves, restrictions, damaged pumps, incorrect rotation, fluid condition, excessive pressure drop, or piping problems can reduce delivered flow.
Repeated resetting without identifying the condition can erase useful fault history and allow the underlying problem to continue. Record the fault and operating conditions first.
Provide the complete model and serial number, voltage, fault code, symptom, thermostat demand, temperatures, flow, airflow, electrical readings, photographs, service history, and completed troubleshooting steps.
Prepare a complete technical record
Identify, Measure, Test, Document, and Then Escalate
Use the correct manual, verify the system conditions, record the results, and submit complete information when requesting technical or parts assistance.