A thermostatic Bypass with a directional valve, special damper and a metal filter is used to prepare the air coming into the hot air ventilator. It protects the hot air ventilator from overheating (when the motor is not working, for example due to a lack of electricity) by shutting the valve and ejecting the air through a damper to another room. Bypass also stabilizes the temperature in the system, by opening a damper and sucking cool air, when the air coming into the ventilator is too hot.
Bypass is also equipped with a metal filter.