Understanding the role of an outdoor sensor in weather compensation
What the sensor actually measures: outdoor temperature in the right spot
The outdoor sensor doesn't "guess" the climate. It measures an air temperature, useful only if it's mounted in the right spot. Aim for a north or northwest facade, sheltered from direct sun, away from a mechanical ventilation outlet, a flue or a window that's often open. Otherwise, the sensor reads too warm or too cold, and the regulation gets it wrong.
How regulation adjusts flow temperature based on the heating curve
With weather compensation, the controller translates outdoor temperature into heating flow temperature. When it's colder outside, it raises the flow temperature. When it warms up, it lowers it. The curve's slope and offset are adjusted to match the building and the emitters. The result: the system heats "at the right level" instead of running all-or-nothing.
Concrete on-site benefits: comfort, consumption, stability
A well-placed sensor gives more consistent comfort, less overheating and a more stable indoor temperature. On the consumption side, lowering the flow temperature helps a boiler condense and improves a heat pump's efficiency. You also gain peace of mind on the settings, with fewer swings and short cycles.
Choosing and placing your sensor correctly: the detail that changes everything
Recommended location: facade, height, areas to avoid (sun, wind, exhaust)
An outdoor sensor is generally mounted on a north-facing facade (or northwest), about 2 to 3 m from the ground. The goal is to measure an "average" temperature, not a wall heated by the sun.
- To avoid. Direct sunlight, under an overhang that traps heat, near a window, a mechanical ventilation extractor, a flue, or a heat pump air discharge.
- Also to avoid. Corners heavily exposed to prevailing winds and areas where water runs down.
Wired or wireless sensor: advantages, limits and use cases in renovation
The wired sensor remains the most stable. No battery, no radio waves, and a reliable signal over time. In return, you need to run a cable, which can be tricky in renovation.
The wireless sensor simplifies installation when running conduit isn't possible. Points to plan for: actual range depending on walls, risk of interference, and battery maintenance.
Compatibilities to check: boiler, heat pump, controller and connection terminals
Before buying, check manufacturer compatibility. Expected sensor type (often NTC), dedicated terminals on the controller, possible polarity, and parameters to enable on the boiler or heat pump side.
On-site settings: configuring weather compensation with method
Setting the slope and curve offset without spending weeks on it
Start simple. Continuous heating over 24 hours, thermostatic radiator valves open, and the outdoor sensor well placed. First adjust the offset to get the correct indoor temperature in mild weather, then the slope to hold comfort in cold weather. Make small adjustments, then let it run 24 to 48 hours before judging. Otherwise, you're correcting for noise, not for actual need.
Adjusting based on emitter type: radiators, underfloor heating, mixed systems
With radiators, the curve is often "steeper" because water temperature needs to rise higher. With underfloor heating, keep a gentler curve and limited flow temperatures to avoid discomfort. In mixed systems, separate the circuits if possible. A direct circuit for radiators, a mixed circuit for the floor. You gain in stability.
Checking the result: temperatures, cycles, client feedback and fine adjustments
Check three things. Actual indoor temperature, flow temperature, and number of start-ups. Too many short cycles usually means a curve set too high. Insufficient comfort in severe cold, slope set too low. Make fine adjustments. Explain to the client that you're aiming for a home with "soft light." Stable, without yo-yoing.
Troubleshooting: common sensor faults and outdoor temperature errors
Typical symptoms: overheating, underheating, on/off cycling, setpoint drift
Inconsistent temperature: an outdoor sensor often drives the weather compensation. If it drifts or fails, the heat pump can heat too hard, not enough, or cycle on/off repeatedly. On the display, the outdoor temperature jumps by several degrees, or stays frozen. Before touching the curve, compare the displayed value with a thermometer placed in the shade.
Simple tests: continuity, ohmic value, cable fault, radio interference
Basic measurements: cut the power. Check continuity to the board, then the sensor's ohmic value. Compare it to the manufacturer's table (often an NTC). A near-infinite or near-zero resistance indicates a cut cable or a short circuit. Also inspect terminals, corrosion, moisture.
- Gently pull on the cable, a loose contact is common at the cable gland.
- Keep the cable away from 230V wiring and dimmers, interference can distort the reading.
- If the sensor is wireless, test batteries, pairing, distance and metal obstructions.
Special cases: influence of an indoor sensor, thermostatic valves and balancing
Hybrid regulation: if an indoor sensor is active, it can correct the weather compensation curve and mask an outdoor fault. Thermostatic valves that are closed too much cause flow to drop, the heat pump quickly rises in temperature then shuts off. Open the reference radiator, check the bypass and rebalance the system, otherwise the setpoint drifts like a compass near a magnet.
What changes in 2026: requirements, financial aid and best practices to highlight for your clients
In 2026, how outdoor temperature-based regulation strengthens real-world performance
A well-tuned heat pump or boiler is one whose consumption matches actual need. Outdoor temperature-based regulation continuously adjusts "weather compensation." With an outdoor sensor, you avoid swings, stabilize comfort and limit short cycles, which are often synonymous with losses.
Link with subsidized projects: consistency with quality requirements and applications
In 2026, financial aid and CEE applications increasingly require consistency between the equipment installed, the settings and proof of commissioning. Highlight the pairing of regulation and configuration. It's a measurable quality that secures the job, especially in whole-house renovation.
Client pitch: explaining the outdoor sensor simply, with supporting evidence (readings)
Put it simply. The sensor is the "thermometer outside" that drives the flow temperature. Show 2 readings, before and after. A lower flow curve, less overheating, and a visible saving over a few days, without promising a magic number.
Key figures
north, away from the sun
Location
2.5 m
Height
±0.5 °C
Accuracy
Frequently asked questions
The sensor alone is rarely eligible as a standalone measure, but it is generally included in an installation controlled by regulation within a funded job. If you install a heat pump or a THPE boiler, your client can access MaPrimeRénov' (amounts based on income), CEE, and sometimes a reduced 5.5% VAT rate on the whole "supply + installation" package if the dwelling is more than 2 years old.
Louis Meneteau
CPO of Argile
