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Centrifugal Roof Exhaust Fans

Centrifugal Roof Upblast and
     Exhaust Fans

Centrifugal Roof Supply Fans

Centrifugal Ceiling and
     Cabinet Fans

Centrifugal Inline Fans

Centrifugal Utility Fans

Propeller Sidewall Fans

Propeller Hooded Roof Fans

Propeller Upblast Roof Exhaust Fans

Propeller Recirculating Roof Fans

Propeller Tube Axial Inline Fans

Propeller Mancoolers

Gravity Ventilators

Roof Curbs



Fan and Ventilators Frequently Asked Questions

Q: Can Centrifugal Inline Fans be mounted outside?
A: If the Centrifugal Inline Fan is Greenheck's Model TCB or TCF the answer is Yes. These fans are constructed with welded housings, which makes them weathertight. If the fan is Greenheck's Model SQ or BSQ, they are not recommended for outdoor mounting. The construction of these fans is such that they are not weathertight.

Q: For a Two-Speed fan, How is the Low Speed Performance determined?
A: The Fan Laws should be used to determine how a fan would perform on Low Speed.

CFM(low) = CFM(high) x [RPM(low) / RPM(high)]
Ps(low) = Ps(high) x [RPM(low) / RPM(high)]2
BHP(low) = BHP(high) x [RPM(low) / RPM(high)]3

Q: Can Belt Drive Inline Axial and Centrifugal Fans be mounted with the motors at 3 or 9 O'clock?
A: Yes. Greenheck's Inline Axial and Centrifugal fan Models TAB, BSQ and TCB are very versatile in how they can be mounted. However, keep in mind that when the fan is mounted with the motor on the side, the motor weight may cause uneven loading on the isolators. This uneven loading can be overcome by mounting the fan on a set of rails that extend beyond the fan on both sides so that the weight of the fan and motor are carried between the outboard isolators.

Q: Can a Solid State Speed Control be used on a Belt Drive Fan?
A: Greenheck does not offer solid state speed controls on belt drive fans because in order to use a solid state speed control, the motors have to be either a PSC (Permanent Split Capacitor) or Shaded Pole type. These types of motors are not used on belt drive fans because they have very low starting and running torque. Belt drive fans have added torque requirements due to bearings, belts, and pulleys, all which hinder the ability of the motor to start the fan or even keep it running if the voltage is dialed down on the speed control.

Q: Are Two Speed Explosion Resistant Motors available?
A: Yes. Two speed explosion resistant motors are available from a number of motor manufacturers. However, these motors are not standard off the shelf motors and may extend the delivery time. These motors also tend to be larger than their non-explosion resistant counterparts resulting in more limitations on whether or not the motor will fit in a given fan.

Q: Are Single Phase Energy Efficient Motors available?
A: Motor manufacturers do offer single-phase motors that are labeled high efficient. Be cautious. Due to a lack of a recognized industry standard, the efficiency levels may vary greatly from manufacturer to manufacturer. Ideally, Greenheck would like to know the required efficiency level when quoting high efficient single-phase motors. In the absence of this information, we will select the motor with the highest efficiency rating.

Q: Are special motors required when using a Variable Frequency Drive (VFD)?
A: Yes. Greenheck supplies specific motors when the fan is to be used in conjunction with a VFD. Motor manufacturers differ on the type of motor they recommend when using a VFD, to insure that the motor and drive are compatible ask your drive supplier what motor characteristics they recommend for their drives.

Q: What is the maximum roof pitch that a fan can be mounted to without correcting the curb for the pitch?
A: As a general rule, the recommended maximum roof pitch is 2:12 or 10 degrees from horizontal. Steeper pitches will increase the possibility of moisture infiltration into the building as a result of water splashing off the roof and entering the fan. For roof pitches greater than 2:12, it is recommended to have a pitched curb, which will allow the fan to sit level and not at an angle.

Q: What information needs to be known in order to properly select a Special Coating?
A: To properly select a special coating for a fan, there are eight questions that should be answered.

  1. What specific chemicals are involved?
  2. What are the concentration levels of these chemicals?
  3. What will the airstream temperature be?
  4. What is relative humidity of airstream?
  5. What amount of time will the fan see this environment? (Continuous or Intermittent)
  6. What part of the country will the fan be located? (Seaboard, Snow country or Desert)
  7. What are the specifications or requirements for this coating?
  8. What part of the fan is to be coated? (Interior, Exterior or Entire)
Q: Can SP, CSP, SQ, BSQ, BCF or BDF model fans be mounted vertically?
A: Models SP and CSP can be vertically mounted, but the backdraft damper on the "B" design may not close depending on the orientation. Models SQ and BSQ can be mounted in any orientation, except for the larger/heavier motors need to be externally supported when the motor is on the side. Models BCF and BDF can not be mounted vertically unless the internal true vibration isolation is removed and replaced with solid studs.

Q: Can we mount a S-CUBE or USGF on the sidewall for emergency smoke?
A: No, the fan body will not support the steel wheel and motor when mounting on a sidewall, the isolators will be put in shear, the fan will not be weatherproof, and will not maintain UL for smoke. Recommend using an inline smoke rated model SWB, TBI, TDI, TCF, AX, QEI for this sidewall emergency smoke applications.

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