HVAC

HVAC

BTI builds balancing systems for HVAC manufacturing: fan wheels, blower assemblies, motor-fan modules and complete air handling units. HVAC is a noise business as much as an airflow business: the residual unbalance a plant accepts on the line is what the building owner hears for the life of the unit.

What BTI Balances in HVAC

BTI balancing machines are built on four platforms (VNR (vertical non-rotator), H (horizontal cradle), VR (vertical rotator) and P (platform suspension)) plus tool holder balancers, spinners and test stands. The platform follows the part geometry and how it has to be held; the correction method follows the material and where there is room to add or remove mass.

Component	Typical platform	Correction method
Centrifugal fan wheels (squirrel cage)	H, P, VNR	Clip-on weight
Axial fan blades and hubs	VNR, VR	Weight-add
Blower and scroll assemblies	P	Weight-add, adhesive
Motor-fan modules	P	Weight-add
Motor rotors and armatures	H	Mill, drill

How a Machine Gets Sized

A BTI machine designation names a platform and a class. A P-5 is the platform suspension base, class 5. The number is a class, not a part weight limit: it describes the size and load envelope of the base. Sizing works from the tooling and the part together, not the part alone. Tooling is not specified until the part prints are reviewed and the fixture is concepted, and the heavier the tooling-plus-part assembly is relative to the class, the less repeatable the measurement becomes. A shop that needs one machine to cover a wide range of parts, and does not need tight repeatability, can run a much broader weight range on a given class than a production program can. Tell BTI the part weight and BTI will name a class the same day. See BTI machine platforms for the full platform and class architecture.

Balance Grade and Tolerance

Balance tolerances are set by ISO 21940-11, which superseded ISO 1940-1. The standard assigns a balance quality grade G, and the permissible residual specific unbalance follows from that grade and the service speed: e_per = (G × 60) ÷ (2π × n) where e_per is permissible residual specific unbalance in g·mm/kg, G is the balance quality grade in mm/s, and n is the service speed in rev/min. Permissible residual unbalance is then U = e_per × m, divided across the correction planes.

Grade	Typical components
G 6.3	Fans, pump impellers, normal electric armatures
G 2.5	Medium and large electric armatures with special requirements

Work out a specific tolerance with the ISO balance tolerance calculator.

Balancing for Sound, Not Only for Bearings

Most balance specifications exist to protect bearings. In HVAC the binding constraint is usually acoustic: an assembly can sit well inside its bearing-life tolerance and still produce a tone the occupant notices. That is why HVAC lines pair balancing with sound and vibration measurement on the same station, and why BTI measures the module as assembled, with its shroud, rather than the bare wheel.

Correction Methods

Method	Where it fits
Drill	Cast and forged parts with material available to remove
Mill	Controlled removal on a defined correction band
Grind	Hardened or finished surfaces
Weld-on weight	Shafts and assemblies, adding rather than removing mass
Clip-on or press-on weight	Wheels, fan wheels and rims
Adhesive and applied weight	Modules, plastics and assemblies

Standards

BTI certifies machines to ISO 21940, SAE International balancing specifications, and DIN specifications. Where a program carries a measurement system capability requirement, BTI evaluates the part and the process first, then confirms what is achievable and commits to it in the machine specification.

Frequently Asked Questions

Related applications: HVAC assemblies, pumps, fans, impellers and blowers, armatures, rotors and motor assemblies, engine cooling modules. Related equipment: NVH and specialized testers.

Browse BTI balancing machines or request a quote.