350 m², 7 climate zones — heating, cooling and humidity held from one setpoint each

Every zone here has three ways to change the temperature: an air conditioner, an underfloor heating loop and — indirectly — a humidifier. Point all three at the same room without a shared rule and they will work against each other. The classic failure is a floor loop that keeps heating right up to the point where the air conditioner starts cooling, and the two then run against one another all evening.

The second problem is the measurement itself. A control loop is only as good as the number it is given, and one sensor reports the temperature at one point on one wall. In a room with a glazed facade, a warm floor and a draught path, other points in that same room differ by several degrees. A single reading makes the loop chase a number that describes almost nothing.

A stuck sensor is worse than a missing one. A missing sensor is obvious; a sensor frozen at a plausible 22 °C looks healthy and quietly holds the whole zone at the wrong temperature.

Each zone runs one rule with a dead band of ±0.5 °C around the setpoint. Below the band it heats, above it cools, and inside the band both outputs are released. That last part is the one people get wrong: holding the previous state inside the band is what lets a heating loop run all the way to the cooling threshold. The band exists to protect compressors and valve drives from short cycling, not to keep equipment running.

A season flag locks cooling out in winter, so a warm afternoon cannot start an air conditioner in a house that is in heating mode.

The temperature a zone acts on is not one sensor but an aggregate of several, published to the zone as a single value. Outliers are rejected against the median of the group rather than averaged in — averaging alone does not protect against a sensor stuck at a plausible but wrong value, it just spreads the error across the zone. With fewer than three readings there is no majority to compare against, so the check stands down instead of guessing.

If no valid reading is left, the outputs hold their last state and the rule logs a warning. Acting on a bad number is worse than not acting.