Greenheck BSQ Belt Drive Square Centrifugal Inline Fan

A square-cabinet inline fan that removes the round-to-square transition

The Greenheck BSQ is the belt-driven member of the SQ and BSQ square centrifugal inline family. It pairs a backward-inclined, non-overloading wheel with a galvanized steel square housing, so the fan connects to rectangular ductwork without the costly square-to-round transition pieces that tubular fans need. The catalogue positions it for indoor clean air duty: intake, exhaust, return or make-up air where space is tight.

Belt drive sizes run from 70 to 420 with airflow up to 27,700 cfm and static pressure up to 4 in. wg when the high-pressure (HP) wheel is selected. That is a long way above the direct-drive SQ sibling, which stops at 5,000 cfm and 2.5 in. wg, so the BSQ is the model to look at when a project needs both volume and pressure from a compact cabinet.

Features printed in the catalogue

• Rigid structural members with formed galvanized steel panels; aluminum construction optional on BSQ sizes 70 to 300.
• Two removable access panels give access to every interior component; the motor can sit top, bottom or side because it is rigidly mounted.
• Drives sized for at least 150 percent of driven horsepower, machined cast iron pulleys factory-set to the required rpm and adjustable for final balancing; static-free, oil-resistant belts.
• Fan shafts ground and polished so the first critical speed is at least 25 percent above maximum operating speed.
• Bearings with a minimum L10 life above 100,000 hours (L50 above 500,000 hours).
• NEMA-1 disconnect switch as standard; each fan carries a stamped nameplate with full model number and serial number.
• AMCA licensed for Sound, Air and FEI; UL/cUL 705 electrical listing is optional and must be specified (file E40001).

Technical specification

Dimensions and weights by size

Weights are for standard galvanized construction with the largest cataloged open drip proof motor, as printed in the catalogue.

Selecting and ordering a BSQ

The model number identifies configuration, wheel pressure level and size, for example BSQ-120 HP, where BSQ means belt drive, SQ means direct drive and HP marks the high-pressure wheel. The catalogue notes the Vari-Green (VG) motor is for direct drive only. Because the catalogue rates performance for installation type B (free inlet, ducted outlet) and excludes accessories, select from the curves for your size and then add the losses of any filter box, damper or guard. Discharge position matters: the catalogue data is for inline discharge, right side discharge gives 108 percent of cataloged performance and left side gives 109 percent, so state the discharge position when you request a quotation.

Installation and operation notes

Install with at least three duct diameters on both inlet and outlet to limit system effect, and keep the motor accessible for service. External isolators, hanging or base-mounted, are recommended. Belt adjustment is done by loosening fasteners, sliding the motor plate and retightening. Fit the optional insulated housing where noise or condensation control is needed; the catalogue lists approximate radiated attenuation of -2 to -13 dB by octave band depending on size group.

Where it is used

The catalogue lists clean-air work in office buildings, schools and hospitals. Greenheck’s product page also lists SASO among the BSQ certifications, which matters for Saudi projects. The BSQ is for clean air only; it is not intended for corrosive, greasy or particulate exhaust.

Accessories and related items

• Gravity or motorized backdraft dampers (WD-330) and opposed-blade control dampers (VCD).
• Inlet and outlet guards, belt guard and motor cover (standard with UL), wiring pigtail.
• Insulated housing (1 in. fiberglass liner), filter box assemblies, motor starters, coatings from Permatector to Industrial Epoxy.
• Browse our HVAC and combustion range for related ventilation products.

What to confirm before ordering

Confirm the drive side and discharge position, whether the high-pressure wheel is needed, and what accessories sit in the airstream, since those losses reduce the cataloged flow. Say if UL electrical listing or aluminum construction is required, because both are options rather than standard.

Documents and supply information

The January 2025 Greenheck catalogue for models SQ and BSQ is attached to this page. Dimensions, weights and performance are quoted as printed there; project-specific curves should come from the selection program. Lead time, stock and certificates are confirmed in the quotation.

Frequently asked questions

What is the difference between SQ and BSQ? SQ is direct drive (sizes 60 to 160, up to 5,000 cfm); BSQ is belt drive (sizes 70 to 420, up to 27,700 cfm).

How much pressure can the BSQ produce? Up to 4 in. wg with the high-pressure wheel, per the catalogue.

Is aluminum construction available? Yes, on BSQ sizes 70 to 300; some drive frame parts may remain steel.

Can it be used outdoors? The catalogue positions the BSQ for indoor clean-air applications such as offices, schools and hospitals.

Is Seven Star LLC the manufacturer? No. Seven Star LLC is an independent supplier in Muscat; confirm size, drive and options before ordering.