Commissioning a heat pump is one of the most critical steps in ensuring its optimal performance, efficiency, and longevity. Whether you're installing an air to water or ground source system, proper commissioning guarantees that the heat pump operates as designed—providing maximum comfort, minimal energy use, and regulatory compliance.

In this installer-focused guide, we’ll walk through the step-by-step process to commission a heat pump system, highlight common pitfalls, and outline key checks for long-term system success.

What Is Commissioning and Why Is It Important?

Commissioning is the final stage of heat pump installation, involving the inspection, testing, and fine-tuning of all components to ensure the system operates according to design specifications.

Benefits of proper commissioning:

• Ensures full manufacturer warranty coverage

• Maximizes Seasonal Coefficient of Performance (SCOP)

• Prevents early component failure

• Optimizes user comfort and control

• Meets compliance standards (e.g., MCS in the UK, EN standards in Europe)

✅ Pre-Commissioning Checklist

Before powering on the system, ensure:

• All pipework is installed and pressure tested

• Electrical connections are correct and secure

• Thermostats and controllers are properly wired

• Heat emitters (radiators, underfloor loops) are flushed and balanced

• Expansion vessels, filters, and buffer tanks are in place

• Outdoor unit is level, secured, and clear of obstructions

Tip: Document system parameters and installation values before startup.

Step-by-Step Heat Pump Commissioning Procedure

1. Fill and Flush the Heating Circuit

• Fill system with clean, softened water

• Add approved inhibitor or antifreeze (if required)

• Use a power flush or magnetic filter to clean loop

2. Bleed Air and Balance System

• Vent air from radiators, underfloor circuits, and pump body

• Balance loops for equal flow rates

• Ensure circulation is smooth and quiet

3. Check Electrical System

• Verify correct voltage and phase

• Confirm polarity and earthing

• Test fuses, RCDs, and safety switches

• Ensure outdoor sensor placement and connectivity

4. System Startup and Control Programming

• Power on the system

• Set heating curves or weather compensation controls

• Configure hot water tank settings (target temps, schedules)

• Adjust flow temperatures per design spec

• Set minimum and maximum compressor speeds (inverter models)

5. Check Refrigerant Circuit (if applicable)

• For split systems or R32/R410A units, check:

• Correct refrigerant charge

• Pressure readings under load

• Subcooling and superheat values

Note: Only qualified professionals should handle refrigerants.

Commissioning Documentation Requirements

Include the following in the commissioning report:

• System design data (heat load, flow temps, emitters)

• Heat pump model and serial number

• Flow rate readings and temperature differentials

• Controller settings and curve configurations

• Electrical and refrigerant test results

• Inhibitor or antifreeze used

• Installer name, date, and certifications

This documentation is essential for:

• Warranty activation

• Subsidy applications

• Building compliance (e.g., EPC rating or MCS)

⚠️ Common Mistakes to Avoid

• Failing to balance hydraulic circuits

• Not setting correct weather compensation curves

• Overlooking hot water priority settings

• Leaving air in pipework

• Incorrectly sizing the expansion vessel

• Ignoring commissioning of smart thermostats or zoning controls

Post-Commissioning Recommendations

• Schedule user handover and explain system controls

• Recommend a service plan and first maintenance check at 12 months

• Educate homeowners about noise, defrost cycles, and energy-saving tips

Conclusion

Proper commissioning is not just a box to tick—it’s essential for ensuring that a heat pump delivers the energy savings and performance it was designed for. By following a structured approach and thorough documentation, installers can set the foundation for years of efficient, low-maintenance operation.