Thermostat shows E2 and heating does not respond correctly; temperature reading may be frozen or unrealistic.

Safety first: Isolate power to the underfloor heating manifold and thermostat at the breaker before working on wiring.

Steps to check:

• Confirm sensor use: On Salus underfloor models (e.g. Salus VS20WRF, VS10WRF, HTRP series), check the installer menu to confirm that a floor sensor is enabled. If no floor sensor is installed but the thermostat is configured to use one, E2 can appear. Disable the floor sensor option if not used.
• Inspect sensor wiring: Remove the thermostat from the wall and check the floor sensor wires at the dedicated terminals (often marked S1/S2 or NTC). Ensure both conductors are firmly clamped and not broken.
• Check continuity: With the sensor disconnected and power off, use a multimeter to measure resistance across the floor sensor leads. A typical Salus NTC floor probe is around 10kΩ at 25°C. Infinite resistance indicates a break; near 0Ω indicates a short.
• Inspect cable route: If the sensor cable runs in the floor screed, check any accessible junction boxes for loose connections or damage. Look for pinched or cut cable where it exits the floor or wall.
• Replace sensor if faulty: If resistance is out of range or intermittent when flexing the cable, replace the Salus floor sensor probe with a compatible NTC sensor specified by Salus.

When to replace thermostat: If a known-good sensor still gives E2 and wiring is correct, the sensor input on the thermostat PCB may be damaged. Replace the thermostat unit.