The sound and alarm indicate something
A flue gas extractor that squeals or grinds often has worn bearings, but a high, constant whistling tone can also mean that the encoder is defective and that the motor is therefore running at full speed. Vibrations and an uneven, humming sound are typically caused by ash and soot on the blower wheel, creating imbalance. A dirty wheel also moves less air, so the stove may trigger a draught alarm without the motor being defective. Remove the flue gas extractor and clean the wheel and housing before replacing the motor.
If the stove gives an alarm even though the flue gas extractor sounds normal, the flue path may be blocked, or a leaking door may draw in false air. If, on the other hand, the problem is that the pellets do not reach the burn pot, the fault lies with the gear motor, and if the heat remains in the stove instead of reaching the room, it is the fan. An overview of all three is available under motors and fans.
Complete with housing or motor only
The flue gas extractor is available either as a complete unit with housing or as a motor with blower wheel for installation in the stove's existing housing. If the housing is intact, the motor alone is the cheapest option, while a cracked or corroded housing requires the entire unit to be replaced. The price difference is typically several hundred kroner.
Universal flue gas extractors are selected according to the blower wheel diameter, typically 120 or 150 mm, the speed and the shape of the outlet, for example straight or angled. All three must match the old one because they determine how much air the flue gas extractor moves and whether it can be connected at all.
When the fault is in the capacitor, encoder or gasket
If the motor hums without reaching speed, or only starts if the wheel is given a push, it is typically the capacitor that is weak. The new one must have the same capacity in µF as the old one, and the value is normally printed on the capacitor.
If the flue gas extractor is running while the stove reports an error in the speed, the encoder may be defective. On flue gas extractors with a core motor, it can be replaced separately, so the entire motor does not need to be replaced.
Every time the flue gas extractor is removed, the gasket should be replaced because a used gasket is compressed and rarely seals again. A leaking joint lets smoke escape and disrupts the negative pressure in the combustion chamber. If joints around the flue gas extractor motor need sealing in addition to the gasket, heat-resistant adhesive is available for this purpose.
