Choosing the right heat pump for underfloor heating: what makes the difference on site
Air/water heat pump or ground source: when to favour one over the other
On underfloor heating, an air/water heat pump often does the job if the home is well insulated and you're targeting low flow temperatures. It installs quickly, without major earthworks. Ground source holds its own when you're after stable performance in winter, with compatible ground and a budget for boreholes or ground loops. It's also a relevant choice when outdoor noise is a sensitive issue.
Low temperature: understanding the heat pump + underfloor heating pairing
Underfloor heating is a low-temperature emitter. In practice, you often target 30 to 40°C at flow, depending on the calculations. On site, check the controls, loop balancing, the mixing valve if present, and the heating curve. A heat pump able to hold these temperatures without strain means comfort with no nasty surprises.
Power and modulation: sizing to avoid short cycling and overconsumption
The classic trap is a heat pump that's too powerful. The result: short cycling, wear, and kWh that spiral. Size based on heat loss, not on the old generator. Favour an inverter compressor with wide modulation to cover mid-season. And take care with commissioning — hydraulic settings and the heating curve often matter more than 1 kW of margin.
Preparing the installation: essential checks before fitting the heat pump
Condition of the underfloor heating: pipework, manifolds, balancing and flow rate
Before connecting the heat pump, inspect the underfloor heating like a plumbing circuit. Locate the loops, check the manifolds, the valves, the flow meters and the purge. Check the pressure, the absence of leaks, then carry out an initial loop-by-loop balancing to guarantee sufficient flow rate and even temperatures.
Water quality and protection: sludge trap, filter, sludge removal if needed
A heat pump doesn't like sludge. Assess the water condition (colour, particles, pH if possible) and fit a sludge trap and a suitable filter, ideally magnetic. If the network is heavily fouled, plan for sludge removal, a rinse, and then treatment to start over with clean water.
Controls and zoning: thermostat, heating curve, sensors and baseline settings
Check the compatibility of the thermostat, sensors and actuators with the heat pump. Activate a heating curve with an outdoor sensor, then set simple flow-temperature baselines. Limited flow temperature, progressive curve, reasonable hysteresis. Well-configured zoning avoids short cycling and stabilises comfort.
Carrying out a compliant heat pump + underfloor heating installation: key steps and points of vigilance
Hydraulic connections: common schematics, buffer tank and water volume
On low-temperature underfloor heating, favour a direct connection if the heat pump operates in the 30 to 40°C range. Otherwise, plan for a mixing valve and a buffer tank to avoid cycles that are too short. Check the minimum water volume required by the manufacturer, the nominal flow rate, and install a sludge trap, magnetic filter, expansion vessel and safety valve.
Commissioning: purging, testing, settings and temperature checks
Fill, pressurise, then purge the manifolds and loops. Run circulation tests, balance the flow rates, then set the heating curve. Check flow and return temperatures, and keep floor-surface temperature under control. Document the commissioning and settings. This is valuable for after-sales service and for 2026 support-scheme files.
Nuisance and placement: acoustics, condensate drainage, maintenance access
Take care with the outdoor unit's placement. Use anti-vibration mounts and respect distances to boundaries to limit noise. Plan for frost-free condensate drainage with a trap. Keep simple access for cleaning, electrical checks and hydraulic maintenance.
Optimising performance after installation: settings to improve comfort and savings
Heating-curve settings: a simple method to stabilise indoor temperature
On an air/water heat pump, the heating curve is your cruising control. The idea is simple: the colder it is outside, the higher the heating water needs to rise — but no higher than necessary. Adjust the slope, then the offset, in small steps. Leave 24 to 48 hours between two settings and aim for a stable indoor temperature, with no jolts.
Scheduling and usage: avoiding harsh reheats and setpoints that are too high
A heat pump likes continuity. Avoid large night-time drops that trigger a strong reheat in the morning. Prefer a reduced mode of 1 to 2°C. Keep a realistic setpoint, often 19 to 20°C. On the hot-water side, don't push the setpoint unnecessarily and check the time schedules.
Maintenance: regular checks to preserve the COP and limit breakdowns
Simple maintenance protects the COP. Clear the outdoor unit, clean the filters, check circuit pressure and the absence of abnormal noise. Also schedule regulatory maintenance by a professional, with a tightness check and settings review.
Support schemes and obligations in 2026: securing your files and compliance
MaPrimeRénov' and the CEE certificates: points of attention for a heat pump installation
For a heat pump, secure the timeline first. Application filed before work starts, signed quote, then a detailed invoice with brand, model, power outputs and accessories. Check that the equipment and installation match the France Rénov' criteria and the applicable CEE standardised operation sheet.
In case of combined schemes, align the information between the MaPrimeRénov' file and the CEE sworn statement. A discrepancy in heated area or product reference is enough to block payment. To go further, see also how to avoid MaPrimeRénov' file rejections.
RGE requirements: documents, traceability and site best practices
RGE compliance is proven with simple but consistent documents. Keep your qualification current, ten-year insurance, delivery notes, technical data sheets, and clearly identify who does what, especially in subcontracting. On site, locating the emitters and the hydraulics avoids nasty surprises.
Attestations and evidence: photos, technical data sheets and documented settings
Put together a pack of evidence. Before/after photos with the rating plate, connection diagram, and dated commissioning. Log the settings (heating curve, temperature, flow rates) and, for refrigerant, the regulatory attestations. You save time on inspections and after-sales service.
