Viessmann Heat Pump Error Codes & Fix Guide
Viessmann Heat Pump Error Codes & Fix Guide (Complete HVAC Expert Guide)
If you’re working with a Viessmann heat pump and see an error code on the display, don’t panic—these systems are designed to diagnose themselves and guide you toward the fault. Whether you’re a homeowner, technician, or HVAC dealer, this guide will help you understand, troubleshoot, and fix Viessmann heat pump error codes like a pro.
About Viessmann Heat Pumps
Viessmann Group is a global leader in heating and renewable energy solutions. Their heat pumps—such as Vitocal 100, Vitocal 200, and Vitocal 300 series—are known for efficiency, reliability, and smart diagnostics.
1. What Are Viessmann Error Codes?
Viessmann heat pumps use a self-diagnostic control system that constantly monitors:
- Temperature sensors (NTC/PTC)
- Compressor performance
- Refrigerant pressure
- Water flow rate
- Electrical components
When a fault is detected, the system displays:
- F Codes → Fault (system stops or limits operation)
- A Codes → Warning (system still running)
2. Types of Viessmann Heat Pump Faults
Electrical Faults
- PCB failure
- Voltage fluctuation
- Wiring issues
Sensor Faults
- Flow sensor error
- Outdoor temperature sensor failure
Refrigerant Faults
- Low refrigerant charge
- High pressure fault
- Compressor overload
Hydraulic Faults
- Low water pressure
- Circulation pump failure
Communication Faults
- Indoor ↔ Outdoor unit error
- Controller failure
3. Complete Viessmann Error Code List
Below is a professional categorized list of common Viessmann fault codes:
F-Series Error Codes
| Code | Description |
|---|---|
| F.0 | General fault |
| F.1 | Flow temperature sensor fault |
| F.2 | Return temperature sensor fault |
| F.4 | Outdoor temperature sensor fault |
| F.5 | DHW sensor fault |
| F.6 | Evaporator sensor fault |
| F.7 | Condenser sensor fault |
| F.8 | Compressor discharge sensor fault |
| F.9 | Suction temperature sensor fault |
| F.10 | High pressure fault |
| F.11 | Low pressure fault |
| F.12 | Flow switch error |
| F.13 | Pump failure |
| F.14 | Compressor overload |
| F.15 | Expansion valve fault |
| F.16 | Defrost failure |
| F.17 | Freeze protection triggered |
| F.18 | Communication error |
| F.19 | EEPROM/PCB fault |
| F.20 | Voltage error |
A-Series Warning Codes
| Code | Description |
|---|---|
| A.1 | Temporary interruption |
| A.3 | Defrost cycle active |
| A.5 | Compressor delay |
| A.7 | Anti-freeze mode |
| A.9 | System optimization |
4. Common Viessmann Error Codes Explained
Let’s break down the most important ones HVAC professionals encounter:
F.10 – High Pressure Fault
Causes:
- Dirty condenser coil
- Blocked airflow
- Overcharged refrigerant
Fix:
- Clean outdoor unit
- Check fan operation
- Verify refrigerant charge
F.11 – Low Pressure Fault
Causes:
- Refrigerant leak
- Blocked expansion valve
Fix:
- Leak detection (nitrogen test)
- Recharge refrigerant
F.12 – Flow Switch Error
Causes:
- Low water flow
- Pump malfunction
Fix:
- Check circulation pump
- Clean strainers
F.13 – Pump Failure
Causes:
- Electrical issue
- Mechanical failure
Fix:
- Check pump voltage
- Replace pump if needed
F.14 – Compressor Overload
Causes:
- High pressure
- Electrical imbalance
Fix:
- Check amps
- Inspect compressor winding
F.18 – Communication Error
Causes:
- PCB failure
- Wiring issue
Fix:
- Inspect cables
- Replace control board
5. Advanced Troubleshooting Guide
Step 1: Read Error Code
Check control panel or app interface.
Step 2: Reset System
- Turn OFF
- Wait 5 minutes
- Restart
Step 3: Check Basics
- Power supply
- Water pressure
- Air filters
Step 4: Sensor Testing
- Measure resistance
- Compare with temperature chart
Step 5: Refrigerant Diagnosis
- Check pressure gauges
- Look for oil traces
6. Sensor Fault Diagnosis
Viessmann systems rely heavily on precision sensors.
Common Problems:
- Open circuit
- Short circuit
- Calibration drift
Testing Method:
- Use multimeter
- Compare ohm vs temperature
7. Refrigerant & Pressure Issues
Symptoms:
- Reduced heating capacity
- Frequent shutdown
- Ice formation
Causes:
- Refrigerant leak
- Dirty evaporator
- Expansion valve fault
Solutions:
- Leak detection
- Recharge system
- Clean coils
8. Electrical & PCB Faults
Key Codes:
- F.18
- F.19
- F.20
Causes:
- Voltage fluctuation
- Burnt PCB
Fix:
- Install stabilizer
- Replace board
9. How to Reset Viessmann Heat Pump
Method 1:
Use reset button
Method 2:
Power OFF → Wait → ON
Method 3:
Reset via controller menu
10. Preventive Maintenance Checklist
Monthly:
- Check pressure
- Clean filters
Quarterly:
- Inspect wiring
- Test sensors
Yearly:
- Full servicing
- Refrigerant check
11. Pro HVAC Diagnostic Tips
Since you’re an HVAC dealer, here are advanced insights:
Check Superheat & Subcooling
- Low superheat → flooding
- High superheat → low charge
Monitor Delta T
- Ideal: 5–10°C
Compressor Amp Check
- High amps = mechanical issue
AI-Based Fault Mapping
Combine symptoms:
- Low pressure + frost → gas leak
- High pressure + noise → airflow issue
12. FAQ Section
Q1. What does F.10 mean on Viessmann heat pump?
It indicates high refrigerant pressure, usually caused by airflow issues or overcharging.
Q2. How do I reset a Viessmann heat pump?
Turn off power, wait 5 minutes, and restart.
Q3. Why does my heat pump show low pressure error?
Due to refrigerant leaks or expansion valve problems.
Q4. Can I fix Viessmann error codes myself?
Basic issues can be fixed, but major faults need professionals.
Q5. How often should servicing be done?
At least once per year.
Final Thoughts
Understanding Viessmann heat pump error codes allows faster diagnostics, reduced downtime, and better service quality. Whether it’s a simple sensor fault or a complex compressor issue, this guide gives you a complete troubleshooting framework.
