We encourage you to read our updated privacy statement.
  1. Home
  2. Resources
  3. Library
  4. FAQs
  5. Products FAQs
  6. Inline Fans FAQs

INLINE FANS FAQs

Answers to your most Frequently Asked Questions about Greenheck inline fans.

Q:
Q:Can centrifugal inline fans be mounted outside?
A:
A:If the fan is a Greenheck model TCB, QEI or QEID, the answer is yes. These fans are available with welded housings or sealed for outdoor use, which makes them weathertight. If the fan is Greenheck's Model SQ or BSQ, they are not recommended for outdoor mounting. These fans are not weathertight.
Q:
Q:Can a solid state speed control be used on a belt drive fan?
A:
A:Greenheck does not offer solid-state speed controls on belt drive fans because the motors must be a permanent split capacitor (PSC) or shaded pole type. These motor types 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:
Q:Can belt drive inline axial and centrifugal fans be mounted with the motors at 3 or 9 o'clock?
A:
A:Yes. Greenheck's inline axial and centrifugal fan Models BSQ and TCB are very versatile in mounting options. 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:
Q:Can inline centrifugal fans be used for continuous high temperature exhaust applications?
A:
A:

Inline centrifugal fans (Greenheck model TCB) are not recommended for high temperature continuous exhaust applications. The reason is based solely on the inline centrifugal fan design, which has the impeller at the inlet of the housing. As seen on the following diagram, the fan housing becomes pressurized and heated to the temperature of the incoming air. Leakage of heated air and heat transfer through the bearing cover and belt tube reduce the life of the bearings and motor. Our recommendation is not to exceed 200° F with inline centrifugal fans.

Q:
Q:Can inline fans be used for kitchen grease exhaust applications?
A:
A:Yes, inline fans (GFC models TCB and QEI) are UL Listed for use in grease exhaust applications. Additionally, these units meet the requirements of NFPA 96 - Ventilation Control and Fire Protection of Commercial Cooking Operations. Greenheck is the only manufacturer that meets both UL and NFPA for inline grease exhaust applications. Our "Easy Access Door" makes routine service and cleaning fast and easy. All service work can be accomplished without removing the fan from the ductwork.
Q:
Q:Can SP, CSP, SQ, BSQ, BCF or BDF model fans be mounted vertically?
A:
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 mount in any orientation, except the larger/heavier motors need external support when the motor is on the side. Models BCF and BDF cannot mount vertically unless the internal vibration isolation is removed and replaced with solid studs.
Q:
Q:Can vane axial fans be used for high temperature exhaust?
A:
A:Typical applications for vane axial fans involve exhausting or supplying clean, ambient air. Greenheck's recommendation for continuous high temperature operation is 110° F for direct drive vane axials, where the motor is in the airstream, and 200° F for belt drive vane axials, where the motor is out of the airstream.

For emergency smoke ventilation involving temperatures above 200° F, please contact us.
Q:
Q:For a two-speed fan, how is the low speed performance determined?
A:
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:
Q:What determines the minimum horsepower requirement for Greenheck centrifugal and industrial fans?
A:
A:

Minimum horsepower for centrifugal and industrial fans is based on either the operating brake horsepower or the minimum starting horsepower of the fan. Operating brake horsepower is an obvious limit to the minimum motor horsepower, since the motor horsepower must exceed the operating brake horsepower for the fan to work. Minimum starting horsepower is based solely on the horsepower required to get the fan wheels rotating. Minimum starting horsepower begins to become a significant factor for single width wheels above size 49 and double width sizes above 44. For example, it is possible to have 49-BISW performance that requires less than one brake horsepower, but the minimum starting horsepower is 7.5 HP.

Q:
Q:What factors prevent fans from not performing as specified?
A:
A:

There are numerous reasons why fans fail to perform as specified. But first, it is important to understand what defines acceptable performance. According to AMCA Publication 200, a fan installed in a ventilation system should expect a tolerance of +/- 7.5% for flow (cfm). In other words, a fan which produces 1,000 cfm in a lab environment should provide a volume flow rate of 925 to 1,075 cfm when installed in a properly designed ventilation system. Volume flow rates which fall below this range are typically the results of variances in system static pressure or mechanical problems with the fan. Common symptoms include:

  • Obstructions in the duct system - closed dampers, closed registers, dirty filters, clogged coils
  • Obstructions in the fan inlet - elbows to close to the inlet, walls too close to the inlet
  • Duct design - improperly designed turning vanes, leaks in supply or exhaust ducts
  • Fan related - impeller running backwards, fan speed too low, impeller dirty or clogged, clearances between inlet cone and wheel cone are incorrect.
Q:
Q:What information needs to be known in order to properly select a special coating?
A:
A:

There are eight questions you need answered to accurately select a special coating for a fan.

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:
Q:Which Greenheck centrifugal fans have a UL Listing?
A:
A:

Greenheck offers centrifugal fans meeting UL Listing criteria that align under three UL Standards: Power Ventilators (UL 705), Power Ventilators for Smoke Control, and Power Ventilators for Restaurant Exhaust (UL-762).

UL-705 is concerned with mechanical and electrical construction that assures safe operation of the fan. UL-705 is offered on: inline models AX, TBI-CA, TBI-FS, TDI, TCB, TCBRS, TCBRU, TCF, QEI(D) VAD(S), VAB(S), TAUB, TAUB-CA and TAUD; lab exhaust fan models Vektor-H, HS, MD, MH, MS, CD, CH and CS; and scroll housing centrifugal models SFB, SFD, USF, FJC, FJI, BIDW, and AFDW.

Power Ventilators for Smoke Control is concerned with the removal of smoke laden, and potentially high temperature vapors in the event of an emergency. This listing is available on: inline models AX, TBI-FS, TCF, QEI(D), TAUB; and scroll housing centrifugal model USF.

UL-762 is concerned with fans designed for the removal of smoke and grease laden vapors with airstream temperatures up to 375º F. UL-762 is available on: inline models TCB and QEI; lab exhaust fan model Vektor-H; and scroll housing centrifugal model USF.