Atlantic W02

Atlantic error code W02 indicates: Atlantic Alféa Excellia / Extensa A.I. / Alféa Hybrid Duo Inverter Heat Pump: Diagnostic fault code W02 registered by the microcomputer controller. Hydronic primary circuit flow and return temperature spread warning.

The primary root cause for Atlantic code W02 is: On Atlantic appliances engineered with co-developed Fujitsu twin-rotary DC inverter outdoor stage, Siemens Navistem / RVS hydraulic regulator, electronic expansion valve with 46 Ω stepper phases, and 10 kΩ NTC flow/return temperature sensors: water temperature spread between flow and return exceeding 12°C in cooling or 15°C in heating due to restricted hydraulic flow Metrological tolerance verification: design Delta T between 5°C and 8°C; minimum flow rate 800 L/h..

To resolve error code W02: Disconnect mains power before servicing. Unplug the harness at the main PCB and use a calibrated digital multimeter: clean inline dirt strainer, bleed radiators/underfloor circuits, and increase Wilo pump speed setting. Inspect contacts for pin oxidation or loose terminals. Replace defective part if out of tolerance, re-energize and clear error: On the Navistem user controller: press OK and hold the 'i' button for 3 seconds to access Specialist mode. Go to line 6700-6800 (Diagnostics), select 'Reset fault log' and set to 'Yes', then press OK. For hard lockout, switch off the 230V/400V mains breaker for 60 seconds to discharge the DC link.

Resetting power (unplugging for 5–10 minutes) clears temporary memory errors. However, if Atlantic code W02 persists, the physical component causing On Atlantic appliances engineered with co-developed Fujitsu twin-rotary DC inverter outdoor stage, Siemens Navistem / RVS hydraulic regulator, electronic expansion valve with 46 Ω stepper phases, and 10 kΩ NTC flow/return temperature sensors: water temperature spread between flow and return exceeding 12°C in cooling or 15°C in heating due to restricted hydraulic flow Metrological tolerance verification: design Delta T between 5°C and 8°C; minimum flow rate 800 L/h. must be inspected or replaced.

Set a digital multimeter to ohms (Ω). Disconnect power and test NTC Temperature Sensor Probe (Thermistor) across Across sensor pins 1-2 (unplugged harness). Expected nominal reading is 4.8kΩ–12kΩ (at 20°C–25°C). Tolerance: Negative temperature coefficient: resistance drops smoothly when warmed with fingers. OL = open circuit..

Standard electrical safety protocol: 1. Disconnect 230V mains power before opening panels. 2. Verify zero voltage at test points. 3. Allow hot water or heating elements to cool below 30°C before handling.