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Zehnder Eversky
17.3.3. Manual reset
When the thermostat has tripped due to overheating detection, it must be manually reset it by pressing the white button
after removing the protective cap. Until the reset has been performed, the fan unit will not be able to restart and the
alarm (23) "electric battery overheating" will always be present.
Before manually resetting the thermostat THS, the cause of the malfunction must be understood and remedied.
17.4. Anti-freeze protection thermostat THA (hot water coil)
The anti-freeze protection thermostat THA protects the hot water coil from freezing in the event that the hot water
production system (device external to the ventilation unit) is not operating and the ventilation unit is operating in full
fresh air mode during periods of low outside temperature (below +5 °C).
When the thermostat THA triggers (the contact opens), the fan unit stops and the DO3 hot water pump output is
activated to force the heating coil to heat up. When the bulb temperature rises above +5 °C, the contact closes and the
fan unit restarts normally.
17.4.1. Location
The anti-freeze thermostat THA is located in the control compartment near the main switch. Its bulb is positioned on the
hot water coil.
17.4.2. Nominal setting of the trip point
The thermostat THA is set to +5 °C at the factory.
17.4.3. Electrical connections
The anti-freeze protection thermostat THA is of type NC (Normally Closed). The contact opens when the bulb
temperature falls below 5 °C. The electrical connection is made between terminals (C) and (2) according to the wiring
diagram in chapter XVIII GENERAL WIRING DIAGRAM.
Location of the anti-freeze thermostat THA and its bulb (central view from below)
Anti-freeze thermostat THA
Thermostat bulb
Hot water coil
