Single-zone control assumes the entire space is uniformly occupied and shares one target temperature. Reality differs: a packing area (8 people, static work) has different needs than a dispatch warehouse (2 people, seasonal peaks) in the same hall. Under unified control the packing area heats both itself and the warehouse.
Three typical zones and their characteristics
Zone A, continuous staff presence. Packing, assembly, quality control. Target 18–20 °C, 24/7 or per shift, fine modulation.
Zone B, intermittent presence. Warehouse, dispatch area, transition corridors. Target 12–14 °C, local boost heating at workstations (radiant tube heater above a dispatch bay), night setback to 8 °C.
Zone C, minimal protection. Cold storage, vehicle bay, plant room. Target 5–8 °C (condensation prevention, equipment protection). No active heating during the day, only protection at outdoor extremes.
Typical savings by zone
A 5 000 m² hall without zones (all 18 °C, 16 h/day): annual consumption ~62 000 kWh of gas, cost €24 800.
Same hall with a 3-zone scheme (A: 2 000 m² at 18 °C; B: 2 000 m² at 13 °C with peaks; C: 1 000 m² at 6 °C):
- Zone A: 2 000 m² × 18 °C = 24 800 kWh (40 % less than unified due to smaller volume)
- Zone B: 2 000 m² × 13 °C = 14 200 kWh
- Zone C: 1 000 m² × 6 °C = 4 800 kWh
- Total: 43 800 kWh, cost €17 520
- Annual saving: €7 280 (29 %)
Hardware that makes it possible
Classic per-unit thermostat control (every unit heater independently switched) is not zoned control, it is ad-hoc control. Real zoned regulation requires:
- Central controller (BMS, Building Management System) with time profiles. Solaronics OPEN-CONTROL (control platform for condensing unit heaters and gas radiant) or equivalent. Defines hourly profiles for each zone separately.
- Modulating equipment (condensing unit heaters, electronically modulated radiant heaters). ON/OFF cycles without modulation produce ±2.5 K swings and higher average consumption.
- Sensor network: minimum 2 sensors per zone (at 1.8 m and 4.5 m) to detect stratification and intervene early.
- Door and curtain interlocks: the controller receives door-open signals and delays heating until they close. Air curtains auto-activate when the door opens.
Implementation steps
- Survey of the existing system (Econergy or equivalent): gradient measurement, identification of uneven occupancy, zone-split proposal. 2–4 hours of work, €800–1 500.
- Control architecture proposal: number of control points, cabling (Modbus / KNX / local bus), sensor placement. A plan with measurement points.
- Controller and sensor installation: 1–2 days for a hall up to 8 000 m².
- Handover and training of maintenance lead: pre-commissioning test, manual profile tuning for the first season.
Typical investment for a 3-zone scheme (controller + 6 sensors + installation + commissioning) for a 5 000 m² hall: €6 000–9 500. Payback against €7 000 annual savings: 10–17 months.
Related: Heat stratification in tall halls shows how zoning combined with a destratifier yields a further 6–10 % saving.
Sensor placement, common mistakes
A sensor near an exterior wall measures wall radiation, not actual target temperature. Common misplacements we see on retrofit calls:
- Thermostat at the opposite end of the hall from the heating unit. The controller receives signal too late, the system swings on/off. Correct: sensor 4–6 m from the heating unit, not flush against wall insulation.
- Sensor below a ceiling lamp. Radiation from lighting biases the reading by 2–3 K. Move half a metre to the side.
- No gradient sensor in stratifying zones. A single sensor at 1.8 m doesn't detect 28 °C under the ceiling. A vertical pair (1.8 m + 4.5 m) is mandatory above 6 m ceilings.