- AHU outlet diameter
- External Static Pressure (ESP)
- Outlet Airflow Velocity
- Room dimensions
- Suspension options
- New or Existing units
- Available Fittings- Elbows (any angle / diameter can be specified within reason), Tees (Various shapes and construction options are available for inlet and connection tees, depending upon the application's requirements), Reducers( inlet and outlet diameter and length of reducer can be specified).
ESP must be 3/8" to 1/2" w.g. and will need lower outlet velocities at the inlet. A minimum 30% pre-filter is recommended to increase the time between cleanings.
Many units may not be able to compensate for the additional static pressure needed to properly inflate the system, so booster fans and dampers may be required for the retrofit.
Soft Start Controls: in order to minimize "start up pop" and unnecessary wear on the ductwork FabriDuct™ reccomends using a ramp up or soft start motor controller on ducts 5,000 up to 10,000 cfm For ducts 10,000 CFM or greater it is expected. This will help eliminate the “popping” effect caused by the initial surge of air flow.
Variable Air Volume (VAV): testing has revealed that FabriDuct™ systems are able to perform at levels 40% below and 50% above standard design. Please notify us if you plan on such requirements.
Two-Speed / Staging Fans: Continuous fan duty is recommended for standard systems in order to reduce wear on the units and FabriDuct™ systems. For large, industrial and commercial installations, you may consider a fan to keep the FabriDuct™ system partially inflated while not in use, so that when the main fan is turned on, there is no wear on units or the FabriDuct™ system and no “popping” effect.
Balancing your system
FabriDuct™ systems are self-balancing. Normally (with sheet metal installations), CFM numbers are displayed beside registers on drawings. With FabriDuct™ systems, there are no registers as the duct is the diffuser. Therefore, balancing is based on the Delivery Area (CFM per square foot of duct), which will be determined during the system design process by our qualified engineers (at no cost) or by your personnel (if/when experienced with FabriDuct™ installations).
Ex. A 65' section of 30" Round at 30 CFM/sq. ft. This kind of specification from you will allow us to design the system to your requirements, or can be provided by us from more basic information from you at no additional cost.
Since the entire duct run is a diffuser and is fabric, SMACNA code (relating ONLY to sheet metal) does not relate to FabriDuct™ installations. Leakage is a necessary feature here!
For additional information, please do not hesitate to call us at
(877) HERO AIR, (423) 510-8225 or via Email at: firstname.lastname@example.org.
Inlet Velocity: for diameter determination
Suggested velocities are 1,500-2,000 FPM.
Calculated as follows: (Qtotal = total airflow in CFM)
Vel=Qtotal / (DIA/ 24)2 x 3.14) (FPM)
Velocity Pressure: average inlet velocity
(velocity pressure is regained as static pressure since system is closed)
Calculated as follows:
VP = (Inlet Velocity / 4005)2 (inch H2O)
To ensure proper inflation:
Keep static pressure at least 30% higher than the VP
Recommended static pressure is 3/8” to 1/2” w.g. (water gauge)
Calculated as follows:
Area = Diameter x 3.14 x Length (ft2)