Commissioning a heat pump: essential checks

Preparing your heat pump commissioning: documents, conditions, and safety

Checking the installation: hydraulic diagram, pipe diameters, network insulation

Before commissioning your heat pump, gather the manufacturer's manual, the as-built file, the validated diagram, and the planned settings. Check the consistency of the pipe diameters, the presence of shut-off valves, the filter, and the air vents. Verify that the network insulation is continuous, especially in unheated spaces, to limit losses and condensation. Run a tightness test, a flush, and a thorough purge before start-up.

Checking the electrical supply: protection devices, cable cross-section, earthing

A heat pump must have a dedicated circuit. Check the breaker, the 30 mA residual current device, a cable cross-section suited to the power and the run, and effective earthing. Confirm the terminal blocks are properly tightened, safety clearances are respected, and the shut-off devices are accessible. Note the voltage and current values at start-up. To go further, see our guide on electrical protection for a heat pump (breaker and RCD).

Securing the site: access to the outdoor unit, condensate drainage, frost risks

Ensure a clear zone around the outdoor unit, a stable support, and anti-vibration mounts. Prepare the condensate drainage with a slope, a trap if needed, and an outlet that won't ice over walkways. In cold weather, protect exposed pipework, anticipate the defrost cycles, and avoid any standing water near the façades.

Essential refrigeration checks before starting the heat pump

Vacuum pull-down and vacuum hold: method, duration, points to watch

Before any start-up, put the heat pump's circuit under a deep vacuum with a suitable pump and a vacuum gauge in microns. Then isolate the circuit and check the vacuum hold for 15 to 30 minutes. A quick rise often indicates residual moisture or a leak. Keep hose lengths short, use core-removed fittings where possible, and run a nitrogen sweep between two evacuations if the network was open for a long time.

Tightness test and leak detection: fittings, valves, brazed joints

Run a pressure test with dry nitrogen, then check every sensitive point. Focus first on fittings, service valves, brazed joints, tappings, and capillaries. Apply soap solution, use an electronic detector, and also check the valve caps. If you find a leak, repair it, redo the pressure test, then restart the vacuum pull-down and hold.

Charging and adjusting the refrigerant: reading pressures and superheat/subcooling

Charge first by weight according to the nameplate and the length of the lines. Let the unit stabilise, then read the pressures and temperatures on the gas and liquid lines. Then adjust superheat and subcooling according to the manufacturer's manual, factoring in the outdoor temperature and the air or water flow rate. An overcharge raises the pressures, an undercharge degrades the COP and can cause frosting.

Hydraulic and airflow adjustments: getting the right flow rates from commissioning onward

Purging, flushing, and water quality: sludge, dirt separator, filters, treatment

Before running the heat pump at full regime, secure the circuit. Purge at the high points and at the circulator. Flush until the water runs clear, especially in a retrofit. Install a dirt separator (ideally magnetic) and a filter on the return. If needed, plan for an inhibitor, chemical flushing, or treatment suited to the make-up water.

Balancing and flow rates: circulators, valves, delta T, weather compensation

Set the flow rates with the balancing valves and adjustment tees, then adjust the circulator (constant or proportional pressure). Check the flow/return delta T according to the emitter and the manufacturer's recommendations. Fine-tune the weather compensation curve in small steps. Good balancing limits short cycling, noise, and overly hot rooms.

Ventilation and air distribution: ducts, vents, room-by-room flow rates (for air/air heat pumps)

On a ducted air/air heat pump, check the airtightness of the ducts, the pressure losses, and the orientation of the vents. Measure and correct the correct flow rates room by room using dampers and vent adjustments. Consider night-time comfort (bedrooms) and sufficient return air to avoid draughts.

Settings, tests, and measurements: validating the heat pump on site

Key parameters: setpoints, weather compensation curve, top-up, hot water modes

After commissioning, adjust the heat pump to suit the building, not just the manual. Calibrate the flow and return setpoints, then adjust the weather compensation curve to get the right indoor temperature without overheating. Set the top-up source: trigger threshold, allowed power, priority to heating or hot water. For hot water, check the comfort and eco modes, the scheduling, and anti-legionella settings based on the client's needs.

Operating tests: cycles, defrosting, noise, vibration, condensate

Run tests under real conditions. Check the stability of the cycles, the number of start-ups, and the absence of rapid on/off yo-yoing. Test the defrost cycle, its frequency, and its return to normal operation. Check the perceived noise outside and in sensitive rooms. Inspect the vibrations, the mounts, and the condensate drainage to avoid dripping and icing.

Measurements to record: temperatures, current, estimated seasonal COP, anomalies

Note everything in a simple report. Outdoor air temperature, flow and return temperatures, hot water, setpoint and room temperature. Current and electrical power at full regime, then during defrosting. Estimate the seasonal COP using dated measurements, ideally via an electricity meter and an energy meter. Also record any fault codes, abnormal noises, flow-rate discrepancies, or setpoint drift.

Compliance and commissioning evidence in 2026: traceability, RGE, and subsidies

Commissioning report: readings, photos, labelling, serial numbers

For a heat pump, the full report secures the job. Record the operating readings at start-up (flow and return temperatures, pressures, current, flow rates if available). Add dated photos of the unit, the connections, the protection devices, and the display. Remember the labelling and serial numbers, plus a copy of the nameplate.

Certificates and obligations: refrigerant handling, maintenance, warranties

If the refrigerant circuit was opened, the refrigerant certificate is essential. Also check the maintenance instructions and the inspection frequency based on the power output. On warranties, some manufacturers make coverage conditional on documented commissioning carried out according to their procedures.

Client file for 2026: documents useful for subsidies and inspections (CEE, MaPrimeRénov')

A clear file avoids pushback. Keep detailed quotes and invoices, RGE proof with the right code, technical data sheets, the commissioning report, photos, and subsidy documents. For CEE, keep the signed sworn statement and the compliance evidence. For MaPrimeRénov', add the subsidy approval and, if requested, the audit or the energy label.