Ductwork turning vanes typically improve pressure drop and degrade acoustical performance. High quality construction and installation of the turning vanes reduce the acoustic penalty.

Recommended Maximum Air Velocities

The maximum recommended velocity for the discharge air duct is 2000 ft/min. The maximum recommended velocity for the return air duct is 1000 ft/min. Limit air velocities below these operating points to minimize the risk of flow turbulence that causes regenerated noise.

The use of round duct and static regain allows maximum discharge air velocities up to 4000 to 5000 ft/min. Round duct also provides substantial attenuation of low frequency noise. However, the potential for flow regenerated noise increases dramatically. Therefore the quality of installation of the ductwork greatly affects the acoustic results of the installed system.

Equipment Room Construction Options

The preferred equipment room wall construction is concrete block. If this is not feasible then a double stud offset wall is suggested. This removes physical contact that would transmit sound through the equipment room wall to the occupied space.

The space between the studs should be interwoven with fiberglass insulation. Two layers of Sheetrock should be used on each side of the wall.

Workmanship details are critical to acoustic performance. All wall and floor penetrations by the ductwork, water piping, and equipment room access doors should be sealed with a flexible material such as caulk and/or gasketing to stop noise and air leaks. Small air leaks can occur at a crack in the wall or with improper fit at a corner in the equipment room. These small leaks can result in a substantial acoustical leak into the occupied space.

The equipment room door should be located away from acoustically sensitive areas like conference rooms. The door should swing out of the equipment room, if possible, so that the low pressure in the equipment room pulls the door in to help maintain a tight seal. Refer also to section Il. EQUIPMENT ROOM LAYOUT LOCATION FOR MAXIMUM USABLE FLOOR SPACE for other door orientation considerations.

Equipment Options

The factory installed flexible horizontal discharge allows multiple duct outlets with multiple factory designed and tested outlet options. This minimizes the risk of acoustic and/or pressure drop problems by avoiding complex transitions close to the fan discharge.