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Installation Do’s and Don’ts

Fans, when connected to ducting, operate best when the ducting is installed in a way that minimises restrictions to the air flow. Fans can be mounted anywhere along the duct system but care should be taken as shown below. All fans make noise but with care, a successful and unobtrusive installation should be achievable.



On systems with more than one inlet/outlet, don’t leave the system unbalanced.

Where more than one inlet/outlet is installed adjust the dampers in the grilles to balance the air flow.

Don’t mount the fan close to inlet
or outlet fitting.

Maximise the distance between the fan and inlet/outlet fitting to reduce noise at fitting.

Don’t position grilles above openable windows or doors. Such positioning causes short-circuiting of the air flow and does not provide proper ventilation.

Grilles should be positioned to ensure ventilation air passes across the room providing ventilation to all areas.

Don’t restrict the flow of air into the rooms being ventilated. Applies to air transfer systems.

It is essential that air is allowed to get into the rooms being ventilated. This can be done by increasing the gap under the door or by installing door grilles. Note: It is impossible to exhaust more air from a room than is allowed to enter it.

Don’t leave ducting slack.

Extend flexible ducting fully and cut to the correct length. Support the duct so that it is straight.

Don’t mount fans close to bends and duct fittings. This will cause higher turbulence and noise.

Position fans more than 500mm from bends and duct fittings.

Don’t squeeze ducting into the fan spigot as this restricts the air flow.

Ducting should be slipped over the fan spigot and taped or clamped into place.

Don’t compress the duct.

Avoid obstructions that will mean the duct will have to be squeezed.

Don’t use ducting longer than is necessary to connect the fan to the grille.

Extend flexible duct fully and cut to the correct length. Support the duct so that it is straight. Remove bends where possible.

Don’t compress the duct when changing direction.

If changes of direction are necessary ensure the duct diameter is maintained
throughout the bend.

Don’t use ducting of a smaller size than the fan spigot.

Ducting should be the same size or larger than the fan spigot to optimise air flow.

Don’t assume the maximum flow rate is required at all times.

Using a 2-speed switch offers high or low air flow selection. It also offers substantially reduced noise levels at the low speed. Variable speed control is also an option.

If the transmission of vibration is a problem do not install fans without vibration isolators.

Fit vibration isolators wherever vibration transmission is likely to be a problem. Available from Fantech.

Don’t mount fans over areas where low noise levels are required.

Mount fans over passageways or over utility areas such as laundries. This will ensure noise levels in bedrooms and similar are minimised.

Don’t install fans where the noise level could be a problem.

If fan noise is likely to be a problem fit a duct silencer, also available from Fantech.