The second pulley is connected to a shaft that drives the fan propeller.
Attic fan belt vs direct drive.
Coming to the advantage of this kind of an industrial fan the biggest advantage is greater efficiency.
Greater efficiency is the biggest pro of direct drive fan configurations.
A well balanced direct drive is far quieter than belt.
Attic mounts installed in the roof or exterior wall of the attic blow air directly out.
Where on a belt drive fan the fan motor shaft has a pulley connected by a belt to a second pulley.
It s balance or lack of balance actually which causes most of the noise.
With a belt drive the fan speed can be easily raised or lowered but there is belt and bearing maintenance to consider with a belt drive there are 2 additional bearings.
This is because of the fact that the amount of friction is greatly reduced in case of this fan when the fan is operating.
Unlike the belt driven fans in case of a direct drive fan there is lesser energy loss.
That would be quiet but would look like a mess from outdoors.
Direct drive models are the most do it yourself friendly because for most no attic joists need to be cut.
Both types are available as direct drive with the fan blade attached to the motor and belt drive with.
Belt drive whole house fans that use an integrated pulley system take longer to install but a belt drive unit provides for a smoother and quieter operation.
Belt drive fans are quieter than direct but still noisy.
There s also no belt residue and these fans cost less to maintain generally speaking because belts don t wear down and break.
Direct drive fans have no power transmission loss since the propeller is directly connected to the motor shaft.
Most whole house fans are relatively easy to install.
However a belt drive fan has power transmission loss due to the friction between the belt and sheaves and due to the drive shaft bearings.
Sizing a whole house fan.