Home Heat Pump Guide

Heat Pump Commissioning: Final Steps Explained

Commissioning is the final and arguably most important stage of a heat pump installation. It is the process where your installer checks every component, configures the system settings, and verifies that everything is working correctly before handing the system over to you.

A properly commissioned heat pump runs efficiently, keeps your home warm, and delivers reliable hot water. A poorly commissioned one can waste energy, leave rooms cold, and lead to unnecessary call-outs. This guide explains exactly what happens during commissioning so you know what to expect and can ensure your installer does a thorough job.

What Is Heat Pump Commissioning?

Commissioning is the systematic process of testing, adjusting, and documenting a heat pump system after physical installation is complete. Think of it as the difference between assembling a car and tuning it for the road — the parts may be in place, but the system needs to be properly calibrated to perform well.

Under MCS standards (which your installer must follow to qualify for the BUS grant), commissioning is not optional. It is a mandatory part of every installation, and the results must be documented in the MCS commissioning certificate.

Commissioning typically takes half a day to a full day, depending on the system complexity. Your installer may schedule it as a separate visit after the main installation work is complete, or it may happen on the final day of the installation.

Pre-Commissioning Checks

Before the system is switched on for the first time, your installer will carry out a series of physical checks:

Electrical Checks

  • Wiring verification: Confirming all electrical connections are correct, secure, and comply with BS 7671 (the IET Wiring Regulations)
  • Earth bonding: Checking that the heat pump, cylinder, and pipework are properly earthed
  • RCD protection: Verifying the dedicated circuit has the correct type and rating of residual current device
  • Voltage and phase check: Confirming the electrical supply matches the heat pump's requirements

Hydraulic Checks

  • System pressure: Filling the heating system and checking that pressure holds steady with no leaks
  • Flushing: Ensuring the system has been properly flushed to remove debris, flux residue, and manufacturing oils
  • Inhibitor: Adding corrosion inhibitor at the correct concentration
  • Air removal: Bleeding all radiators and checking the automatic air vent on the heat pump is functioning
  • Expansion vessel: Verifying the pre-charge pressure on expansion vessels for both heating and hot water circuits

Outdoor Unit Checks

  • Clearances: Confirming adequate airflow space around the unit — typically 300mm minimum at the sides and rear, with unrestricted airflow at the front
  • Base: Checking the concrete base is level and anti-vibration mounts are correctly fitted
  • Refrigerant lines: Inspecting insulation on all refrigerant pipework
  • Condensate drain: Ensuring the defrost water drain is correctly routed and will not cause ice formation in winter
  • Distance: Verifying the unit meets distance requirements from boundaries and openable windows

System Configuration and Settings

This is the most technically important part of commissioning. Getting these settings right determines how efficiently your heat pump runs and how comfortable your home feels.

Flow Temperature Settings

The flow temperature is the temperature of the water the heat pump sends to your radiators or underfloor heating. Setting this correctly is critical:

  • Underfloor heating: Typically 30-40°C
  • Oversized radiators: Typically 35-45°C
  • Standard radiators: Typically 40-50°C (some may need upgrading)

Lower flow temperatures mean higher efficiency. Your installer should set the flow temperature as low as possible while still keeping every room comfortable. This may involve adjusting individual radiator thermostatic valves (TRVs) and checking that each room reaches its target temperature.

Weather Compensation

Weather compensation is a key feature that adjusts the flow temperature automatically based on the outdoor temperature. When it is mild outside, the heat pump sends cooler water to the radiators; when it is cold, it sends warmer water.

Your installer will set the weather compensation curve — a graph that maps outdoor temperature to flow temperature. Getting this curve right typically requires some fine-tuning over the first few weeks of operation, which is why many installers offer a follow-up visit.

Hot Water Settings

  • Target temperature: Usually set to 48-52°C for daily use
  • Heating schedule: Programming when the heat pump heats the hot water cylinder
  • Legionella cycle: Setting up the weekly pasteurisation cycle (heating to 60°C to kill bacteria)
  • Immersion heater backup: Configuring when the backup immersion heater activates (if at all)

Defrost Settings

Air source heat pumps need to defrost periodically in cold weather. The commissioning process includes checking the defrost cycle operates correctly — the heat pump should sense ice build-up on the evaporator and run a short defrost cycle to clear it.

Performance Verification

Once the settings are configured, your installer should verify the system is performing correctly:

Room-by-Room Temperature Check

The installer should check that every room reaches its design temperature. This may involve:

  • Measuring the flow and return temperatures at each radiator
  • Adjusting TRV settings
  • Balancing the system by adjusting lockshield valves to ensure even heat distribution
  • Checking for cold spots or radiators that are not heating fully

Electrical Consumption Check

A good installer will take initial meter readings and note the heat pump's power consumption under different operating conditions. This provides a baseline for monitoring future running costs.

Noise Level Assessment

The installer should verify that noise levels at the nearest window and property boundary comply with the MCS planning standards — typically no more than 42dB at the nearest neighbouring window. This is especially important if the heat pump placement is close to neighbouring properties.

Documentation You Should Receive

At handover, your installer must provide comprehensive documentation. Do not accept the installation as complete without the following:

  • MCS certificate: Your official certification confirming the installation meets MCS standards — essential for the BUS grant
  • Commissioning record: A detailed record of all settings, measurements, and checks carried out
  • Electrical certificate: An Electrical Installation Certificate or Minor Works Certificate for the new circuit
  • Building regulations notification: Confirmation that the installation has been notified to your local authority building control (usually done automatically through MCS)
  • Manufacturer's warranty registration: Proof that the heat pump warranty has been registered with the manufacturer
  • User manual and operating instructions: Both the manufacturer's manual and a site-specific guide explaining how to operate your system
  • Emergency contact details: Who to call if something goes wrong

The Handover Process

A proper handover is not just handing over paperwork. Your installer should spend time walking you through the system:

What Your Installer Should Explain

  • How to use the controller and thermostat
  • How to adjust heating schedules and temperatures
  • What the normal operating sounds are (so you know what is normal vs. a problem)
  • How to check system pressure and top it up if needed
  • What to do if an error code appears
  • When to book annual servicing
  • How to maximise efficiency (keeping flow temperatures low, not overriding the system)

Do not be afraid to ask questions. This is your opportunity to understand your new heating system. A good installer will be patient and thorough — they want you to use the system correctly because it reduces call-backs.

After Commissioning: The First Few Weeks

The first few weeks with a heat pump are an adjustment period. Here is what to expect:

  • Settings may need tweaking: Weather compensation curves often need fine-tuning once the system has been running in real conditions for a while
  • It feels different from a boiler: Radiators may feel cooler to the touch than with a gas boiler — this is normal and intentional. The room should still reach the right temperature
  • Run times are longer: Unlike a boiler that blasts heat for short periods, a heat pump runs for longer at lower intensity. This is more efficient, not a fault
  • Monitor your energy use: Keep an eye on your electricity consumption to check it aligns with the estimated running costs

Many installers offer a follow-up visit 4-6 weeks after commissioning to review performance and make adjustments. Take advantage of this — it is one of the most valuable parts of the service.

Signs of Poor Commissioning

Unfortunately, not all commissioning is done well. Watch out for these warning signs:

  • Flow temperatures set above 55°C for radiators (this suggests the system has not been properly optimised)
  • Weather compensation not enabled
  • Rooms that never reach a comfortable temperature
  • The heat pump cycling on and off frequently (short cycling)
  • Unusually high electricity bills compared to the estimated running costs
  • No commissioning paperwork provided

If you notice any of these issues, contact your installer promptly. Poor commissioning can usually be corrected with a return visit and proper adjustment of settings.

Frequently Asked Questions

How long does commissioning take?

Typically half a day to a full day. Complex systems with multiple heating zones, underfloor heating, and a buffer tank may take longer.

Can I commission the heat pump myself?

No. Commissioning must be carried out by your MCS-certified installer. It requires specialist knowledge, tools, and access to the manufacturer's commissioning software. DIY commissioning would also void your warranty and BUS grant eligibility.

What if my installer does not commission the system properly?

If you believe commissioning was inadequate, contact your installer first. If they do not resolve the issue, you can raise a complaint through the MCS scheme, which has a consumer code of practice and dispute resolution process.

Do I need to be home during commissioning?

Yes, ideally. The handover requires you to be present so the installer can explain how to use the system. It is also your opportunity to raise any concerns.

Will the installer adjust settings after commissioning?

Most reputable installers offer at least one follow-up visit to fine-tune settings based on how the system performs in real conditions. This is especially important for weather compensation settings.

Is commissioning included in the installation cost?

Yes. Commissioning is a mandatory part of any MCS installation and should be included in the quoted installation price. It is not an optional extra.

Getting a heat pump installed? Get free quotes from MCS-certified installers who include thorough commissioning as standard. Read our installation guide for the full process, or check our suitability checker to see if a heat pump is right for your home.