FFU and Terminal Air Purification Equipment

AC Fan Filter Unit

A cost-conscious FFU built around a permanent-split-capacitor AC motor, local speed adjustment and a replaceable high-efficiency filter module.

PSC AC Induction Motor
Local Rotary Speed Control
Forward-Curved Blower Wheel
Wide Voltage Configuration Range

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Product Introduction

The AC fan filter unit uses a permanent-split-capacitor induction motor and forward-curved blower wheel to produce filtered supply air from a conventional single-phase circuit. A local rotary controller adjusts motor voltage for commissioning and periodic rebalance, while the accessible junction box keeps mains connections separate from the filter chamber. The mechanically simple drive is suitable where individual unit control and economical replacement are preferred over digital networking.

Key Features

The PSC motor provides a familiar single-phase drive architecture with readily understood field controls.

A guarded rotary potentiometer permits local airflow trimming without software or a communication network.

The forward-curved wheel develops useful pressure at moderate rotational speed in a compact top-mounted scroll.

A separate terminal enclosure keeps line-voltage connections away from the clean-air path.

Customer Product Concerns

An AC FFU is often selected for straightforward local operation, so the design must balance first cost, controllability and service access.

A fixed-speed AC blower supplies too much air to one ceiling bay and makes system balancing difficult.A dedicated rotary speed controller lets the commissioning technician trim each PSC motor independently.

Line-voltage wiring installed beside the filter seal complicates service and risks damaging the gasket.A top-mounted junction box provides a clear cable gland and terminal area outside the filter interface.

High motor speed can create an objectionable tonal sound above occupied workstations.A correctly sized forward-curved wheel reaches the required face velocity at a moderate operating point.

Replacing an entire proprietary control board extends downtime for a simple fan fault.The conventional PSC motor, capacitor and analog speed controller can be inspected as separate service components.

Typical Applications

Small independent cleanroomsRetrofit ceiling bays with local controlsCompounding support areasLaboratory clean benches and enclosuresFacilities standardizing on conventional AC maintenance parts

Technical Parameters

Representative dimensions and materials for a locally controlled PSC-motor AC fan filter unit are shown below.

Core Material	Galvanized-steel plenum, PSC AC motor, forward-curved centrifugal wheel and micro-glass HEPA or ULPA filter
Panel Thickness	320-420 mm overall module depth
Effective Width	575-1170 mm nominal ceiling-grid width
Maximum Length	Up to 1170 mm standard module length
Steel Facing Thickness	0.8-1.2 mm galvanized-steel plenum and service panels
Core Density	Approximately 85-115 kg/m³ nominal compacted density of the micro-glass final-filter pack
Thermal Conductivity	Approximately 0.035-0.045 W/(m·K) for the dry final-filter pack installed in the AC-driven FFU
Surface Finish	Natural passivated zinc interior with optional white powder-coated exterior and diffuser
Joint Type	Ceiling-grid flange with neoprene perimeter gasket and a compression-sealed removable filter frame
Customization	Available based on the intended application and operating environment.

Available Options

115, 208-230 or 277 V single-phase configurationForward-curved or backward-curved fan wheelLocal rotary or wall-mounted speed controllerBench-top or room-side replaceable filter

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