Fume Hood VAV Controller | External Damper Actuator Control

This fume hood controller is built for variable-air-volume exhaust projects in which the controller and damper actuator are selected as separate components. It can derive demand from a sash-position signal or a face-velocity sensor, command an external actuator, and use airflow-related feedback to support setup of the exhaust control loop. The arrangement gives the project team freedom to coordinate the controller with a butterfly damper, Venturi air valve, single actuator, or engineered multi-actuator assembly without treating one factory actuator package as mandatory.

• Use it when the actuator must be selected around the airflow-control device, torque or thrust requirement, motion, fail position, and project control sequence.
• Choose sash-position demand when opening geometry is the defined control input; choose direct face-velocity feedback when a velocity sensor is the defined input.
• Coordinate the controller revision with the required analog signals, relay functions, local panel, occupancy input, temperature input, and RS485 Modbus RTU network.
• Commission actual airflow and hood response. An actuator command or position signal alone does not demonstrate that the required face velocity has been achieved.

The product is made to order as part of a project-specific control package. The quotation and approved documents must identify the controller version, external actuator, airflow-control device, sensors, panel, I/O allocation, BMS points, alarm and emergency sequence, supplied scope, and site acceptance method.

Where The External-Actuator Fume Hood VAV Controller Fits

The controller belongs between the hood demand inputs and the exhaust airflow-control device. It is intended for a variable-air-volume fume hood where a separately selected actuator moves a butterfly damper or Venturi air valve in response to the required exhaust condition. This split arrangement is useful when the project specification, existing valve, available mounting space, required motion, or preferred actuator brand prevents the use of an integrated controller-actuator assembly.

How It Fits Into The VAV Control Loop

A project can use sash position to represent changing hood demand or use a face-velocity sensor to provide direct velocity feedback. The controller processes the selected input, applies the configured control logic, and sends an analog command to the external actuator. The actuator then changes the opening of the airflow-control device. Airflow feedback and the project pressure coefficient support field adjustment, while the final hood test verifies whether the installed system delivers the required response at the working opening conditions.

This sequence separates five different facts that should not be confused: the sash opening describes geometry; the face-velocity sensor describes air speed at its measurement location; the airflow pickup and pressure relationship support volume estimation; the actuator command requests movement; and the completed hood test evaluates the resulting ventilation performance. A useful submittal and commissioning record identifies all five.

Controller And System Boundary

The controller body is one component of the control package. The external actuator, butterfly damper or Venturi air valve, sash-position device, face-velocity sensor, airflow pickup, local operator panel, transformer, field wiring, BMS programming, installation, air balancing, and acceptance testing must each be assigned as included, optional, by others, or pending confirmation. The product page describes the controller family; the quotation, wiring diagram, point list, sequence of operation, and approved equipment schedule define the supplied project version.

Product Selection Summary

Choose This Controller When

Choose this fume hood controller when the ventilation design requires a separate control unit and an external actuator. The application should have a defined hood demand signal, a compatible airflow-control device, an available feedback method, and a commissioning plan that verifies the completed exhaust loop.

• The hood uses variable exhaust based on sash position or direct face-velocity input.
• The butterfly damper or Venturi air valve requires an actuator selected separately for its motion, load, interface, and fail behavior.
• The project can coordinate analog command and feedback, relay functions, local-panel communication, and RS485 Modbus RTU points.
• The contractor can commission the pressure coefficient, airflow feedback, actuator action, alarms, emergency operation, and actual hood response.

Conditions That Require Project Review

Do not select the controller from the product name alone. Confirm whether the demand signal comes from a resistive sash-position device or a voltage-output face-velocity sensor; whether airflow feedback is available; and whether the selected hardware revision matches the required 0/2-10 V, 0-10 V, or 4-20 mA interface. The available product documents use more than one signal description, so the approved wiring diagram and point list must identify the delivered version.

The external actuator review must cover supply voltage, command and feedback type, electrical load, rotary or linear movement, torque or thrust, travel, direction, mounting, linkage, normal position, fail position, and required operating speed. A combined airflow-control device with multiple actuators also needs a defined quantity, power arrangement, command distribution, feedback strategy, synchronization method, and response to one actuator failing. The published product information confirms multi-actuator capability but does not define one universal arrangement.

Information Needed To Configure the Product

Provide the hood type, sash arrangement and opening dimensions; control mode; target face velocity; minimum, normal, maximum, and emergency exhaust conditions; airflow measurement method; damper or valve type and size; external actuator data; power; signal and relay requirements; local panel; occupancy and temperature functions; BMS protocol and point list; failure sequence; quantity; destination; and responsibility for installation, balancing, commissioning, and acceptance.

The documented project configuration should identify the controller revision, input/output schedule, sensor and panel scope, actuator and airflow-device coordination, wiring and communication requirements, required confirmations, supplied documents, and commercial pricing. That documented configuration defines the controller package supplied for the installation.

Key Specifications

Controller, I/O And Environmental Data

The following data describes the documented FHC12 controller family. Signal allocation, connected loads, sensors, actuator, local panel, airflow-control device, and BMS points remain project-specific. The approved controller revision and wiring schedule must be checked before procurement or field wiring.

Controller Dimensions And Mounting Envelope

The dimension drawing should be used to reserve controller mounting space and access to the terminal side. It shows the enclosure and mounting features only; it does not include clearance for cable bend radius, service access, the external power supply, local panel, sensors, actuator, or airflow-control device.

• Body face shown as 136.0 mm by 65.0 mm.
• Mounting-ear width shown as 146.5 mm.
• Overall lower-view length shown as 155.6 mm.
• Side profile shown as 79.0 mm, with a 36.0 mm body-depth label.
• A separate lower-view dimension is labelled 37.0 mm.

These values are individual labels from the product drawing and should not be merged into an assumed length-by-width-by-height tolerance. The approved dimensional drawing for the ordered controller revision governs mounting holes, terminal access, panel layout, and installation clearance.

Control Inputs And Operating Functions

Sash-Position Demand Control

In sash-position control, the controller reads a resistive position signal and uses the configured hood opening geometry and target face-velocity requirement to establish the exhaust demand. The position input describes how far the sash has moved; it does not directly measure air speed. The current wiring diagram labels the position input as 5-10 kOhm, but the supplied sensor, usable travel, linkage, cable arrangement, and controller revision must be confirmed together.

From Sash Opening To Required Exhaust Airflow

The project setup needs the effective opening width, the relationship between sensor movement and sash opening, and the required operating states. During commissioning, the contractor should check the closed and open references, confirm that the demand changes in the correct direction, and compare requested airflow with the measured exhaust condition. Horizontal, combination, or multiple-sash arrangements may require additional position logic or aggregation outside the controller; they should not be assumed from a single input label.

Direct Face-Velocity Control

In direct face-velocity control, a voltage-output sensor supplies the measured velocity signal. The controller compares the input with the configured requirement and changes the external actuator command to move the airflow-control device. This mode is appropriate when the project explicitly uses face velocity as the feedback variable and defines the sensor location, output, installation method, calibration procedure, alarm thresholds, and response checks.

From Measured Velocity Error To Actuator Command

The control loop still depends on the actuator, damper or valve, available duct pressure, fan response, hood geometry, and air balancing. A stable sensor reading does not by itself prove adequate containment, and an actuator reaching its commanded position does not prove that the required face velocity has been delivered. Commissioning must test the installed hood at the specified sash positions and operating states, including the intended alarm and emergency conditions.

Differential-Pressure Airflow Feedback And Coefficient Setup

The controller includes an airflow-related differential-pressure measurement function and allows the pressure coefficient to be configured. That coefficient connects the installed pickup and pressure signal to the project airflow calculation. It is not a universal factory constant. Pickup geometry, tubing, flow direction, measurement location, straight-duct condition, leakage, airflow-device arrangement, and the selected calculation method affect the field result.

Emergency Exhaust, Airflow Alarm, Energy-Saving And Occupancy Functions

Documented operating functions include energy-saving mode, one-button emergency exhaust, and audible and visual alarm. The controller also provides an occupancy dry-contact input and an exhaust-air temperature input that can participate in a project-defined mode or alarm sequence. These interfaces make the sequence configurable; they do not define the sequence automatically.

External Actuator Architecture

Why The Controller And Actuator Are Separate

The separate architecture lets the airflow-control device and actuator be selected around the actual duct and control requirement. The controller can be mounted where its terminals and communication wiring remain accessible, while the actuator is matched to the butterfly damper, Venturi air valve, or engineered linkage. This can simplify a retrofit that retains an existing valve, a project that specifies a preferred actuator manufacturer, or an assembly that cannot use the mechanical interface of an integrated controller-actuator.

Electrical Compatibility Checks

Start with the exact controller and actuator revisions. Confirm power source, electrical load, isolation requirements, command type, command range, feedback type, feedback range, common reference, shielding, grounding, and the behavior expected when the command or feedback signal is lost. The wiring diagram shows voltage-type command and feedback terminals, while published product material also describes 0-10 V / 4-20 mA configurations. Confirm the applicable configuration before wiring or ordering the external actuator.

Check whether the controller output directly drives the actuator input or whether an interface, relay, power module, or separate transformer is required. Relay-contact ratings are limits for the published contact arrangement, not permission to connect any field load. Inductive loads, line-voltage circuits, overcurrent protection, separation from low-voltage signals, and local electrical rules must be handled in the project electrical design.

Mechanical Compatibility Checks

For a rotary actuator, verify shaft geometry, rotation angle, torque requirement across the pressure and seal condition, mounting orientation, bracket, linkage, rotation direction, end positions, and access for service. For a linear actuator, verify stroke, thrust, linkage geometry, side loading, mounting points, end limits, and the relationship between travel and valve position. Neither rotary nor linear actuator performance should be inferred from the controller model.

Multiple Actuators On A Combined Airflow-Control Device

XICHENG documentation states that the controller can be used to control multiple actuators on a combined airflow-control device. This establishes an available project capability, but not a universal quantity or wiring method. The design must define how many actuators are used, how they are powered, whether one command is distributed or separate outputs are required, how feedback is collected, and how mechanical travel is synchronized.

Fail Position, Load And Synchronization Review

Define the required position for loss of controller power, actuator power, command signal, feedback signal, sensor input, panel communication, and BMS communication. Then confirm that the chosen actuator and mechanical assembly can deliver that behavior. Spring return, electronic fail-safe operation, hold-last-position logic, and driven-safe-position logic are different architectures; none should be implied unless it appears in the approved actuator schedule and sequence.

The final selection record should include actuator make and model, voltage, load, signal ranges, motion, torque or thrust, travel, speed, fail action, feedback, mounting components, quantity, synchronization method, and supplied scope. Those fields make the external-actuator flexibility useful without turning compatibility into an unsupported universal claim.

Valve And System Compatibility

Butterfly damper Integration

A butterfly damper package needs a compatible actuator, shaft or linkage, sufficient torque, correct rotation, defined minimum and maximum positions, and an airflow measurement arrangement suitable for commissioning. The controller supplies the control logic and project-defined command; it does not establish the damper diameter, material, leakage class, chemical resistance, pressure limit, or blade performance. Those fields come from the selected damper schedule.

Venturi Air Valve Integration

The controller can also be applied with a Venturi air valve when the valve and external actuator accept the approved control strategy. Confirm whether the valve uses a linear or rotary actuator, how airflow feedback is generated, which pressure conditions apply, and whether one or several valve bodies are used. The word Venturi does not by itself confirm pressure independence, airflow range, accuracy, coating, or response for the supplied assembly.

Controller Scope Versus A Complete Control Package

A complete hood control loop includes more than the controller. Assign each component and responsibility before ordering.

Applications And Project Fit

Variable-Air-Volume Fume Hood Exhaust

The primary application is a laboratory fume hood whose exhaust demand changes with sash opening, measured face velocity, operating mode, or an approved combination of these inputs. The controller is a good fit when the design intentionally separates control logic from the actuator and can define the sensor, airflow-control device, feedback, alarm, emergency, BMS, and commissioning requirements.

New-Build And Retrofit Conditions

For a new installation, coordinate the hood opening, duct route, required exhaust states, available pressure, airflow-control device, actuator, sensing, panel, power, communication, and acceptance test before equipment release. The separate architecture can accommodate project-specific actuator choices, but it also requires a clear responsibility schedule between the hood supplier, controls contractor, mechanical contractor, balancing agency, and BMS integrator.

For a retrofit, record the existing valve or damper, actuator, sensor, transformer, wiring, panel, airflow pickup, fan or VFD, and network. Confirm the mechanical condition and identify which existing components will be retained. Similar-looking terminals or signal labels are not enough to prove compatibility. The retrofit plan should include a controlled changeover and a full recommissioning test.

When This Product Is Not The Right Controller

Do not use this product as a room-pressure controller, a stand-alone airflow monitor, a fire or smoke damper controller, a certified safety shutdown device, or a complete fume hood ventilation package. It is also a poor fit when the project cannot define or verify the external actuator, sensor strategy, airflow device, control sequence, and acceptance method. A fixed-volume hood may require a simpler control architecture rather than a VAV controller.

When Another Controller Should Be Evaluated

Choose an integrated fume hood controller with VAV actuator when controller and actuator should be supplied as one matched package. Evaluate the fume hood face velocity controller when direct face-velocity feedback and its integrated actuator define the product, or the sash position fume hood controller when resistive position demand and an integrated actuator are preferred. A planned automatic sash fume hood controller should be evaluated when powered sash operation is part of the required function.

Installation, Wiring, And Commissioning

Mechanical And Electrical Checks Before Installation

Reserve a dry, accessible mounting location within the documented controller environment. Allow space for terminal access, cable routing, shielding, service removal, and separation between low-voltage signal wiring and line-voltage relay circuits. Confirm the controller revision, approved dimension drawing, power source, protective device, grounding method, actuator load, sensor types, local panel, airflow pickup, relay loads, and network before terminating wires.

Wiring Terminal Reference

The diagram below organizes the published FHC12 terminal functions. It is a product reference, not a project wiring release. The illustrated external power-supply block is labelled 24 VAC, 3 A; that label describes the shown supply arrangement and must not be treated as the controller’s internal power consumption. Use the controller specification, connected-load calculation, approved wiring diagram, and local electrical requirements to select the final supply and protection.

Control, Panel And Communication Coordination

Before network integration, test controller power, input scaling, actuator command, actuator feedback, relay outputs, sensor values, and the local operator panel as stand-alone points. Then assign the RS485 address and documented communication settings, connect the network with the approved topology, and verify each required point against the BMS point list. A successful network connection does not prove that the physical airflow loop is operating correctly.

Airflow Calibration, Functional Testing And Acceptance

Commission in a controlled sequence: verify sensor zero and direction; verify sash or face-velocity input; stroke the external actuator; confirm damper or valve direction and end positions; check airflow pickup and tubing; establish the pressure coefficient using the approved reference method; compare airflow feedback across the required states; and tune the control response without creating unstable movement or excessive overshoot.

Test occupied and energy-saving operation, low-airflow alarm, audible and visual indication, emergency exhaust, temperature-related sequence where used, relay outputs, panel commands, BMS points, communication loss, sensor failure, actuator failure, and power recovery. Complete the specified hood face-velocity or containment acceptance procedure after the exhaust loop is commissioned. Record settings, measured results, open items, final point assignments, and the approved controller, actuator, sensor, damper or valve revisions for handover.

How To Select And Specify The Controller

Define The Hood And Control Objective First

Begin with the fume hood, not the controller model. Record the hood type, sash configuration, effective opening dimensions, normal operating opening, target face-velocity requirement, minimum and maximum exhaust conditions, emergency state, diversity or energy-saving requirement, available duct pressure, fan arrangement, and acceptance method. Then decide whether the controller will use sash position, direct face velocity, or a documented combination of demand and airflow feedback.

The control narrative should explain what changes the exhaust demand, what value is controlled, how alarms are generated, which state has priority, and what the system should do after sensor, actuator, communication, or power failure. This prevents the hardware schedule from becoming a list of interfaces without an agreed operating result.

Match The Controller To Sensors, Actuator And Airflow-Control Device

For the controller, specify the power version, required analog inputs and outputs, relay assignments, local-panel connection, occupancy and temperature functions, airflow-feedback arrangement, pressure-coefficient setup, and Modbus RTU requirements. For each sensor, define the measured variable, range, output, power, mounting, cable, calibration, and supplied scope. For the actuator, define voltage, load, command, feedback, motion, torque or thrust, travel, speed, direction, fail position, mounting, and quantity.

The butterfly damper or Venturi air valve schedule should state type, size, body and exposed-part materials, connection, operating pressure condition, airflow range, arrangement, installation orientation, and measurement provisions. If several actuators or valve bodies are used, add the power, command-distribution, feedback, synchronization, and failure-monitoring method.

Confirm The I/O, BMS, Alarm And Failure Sequence

Issue a point list that assigns every analog input, analog output, dry contact, relay, panel value, alarm, status, setpoint, override, and network point. Include RS485 topology, address, baud rate, parity, register map, polling responsibility, and loss-of-communication behavior. The controller specification should also assign who supplies, wires, configures, balances, tests, and accepts each component.

Datasheet And Project Review

Technical Data To Confirm Before Approval

The product-family data establishes that FHC12 is a separate fume hood controller with sash-position or face-velocity input paths, airflow-related differential-pressure measurement, configurable pressure coefficient, external-actuator control, relay outputs, local-panel communication, and RS485 Modbus RTU. It also establishes the documented power and environmental options and the controller envelope shown in the dimension drawing.

Project approval must define the controller hardware and software revision, selected control mode, sensor types and scaling, external actuator, airflow-control device, input/output allocation, relay loads, power supply, panel, network settings, alarm thresholds, emergency sequence, failure behavior, coefficient and calibration method. The product page does not replace these project values, and a value documented for one revision should not be applied silently to another.

Technical Submittal Contents

The submittal should include, where applicable, the product data sheet, controller and panel dimensions, terminal schedule, project wiring diagram, I/O and BMS point list, sequence of operation, sensor details, actuator data, damper or valve schedule, power and protection requirements, mounting information, communication settings, configuration record, commissioning procedure, and acceptance criteria. Multi-actuator arrangements should add a power, synchronization, feedback, and failure-monitoring diagram.

After installation, retain the approved documents together with final settings, airflow and face-velocity test results, alarm and emergency test records, network point verification, open-item closeout, and equipment revisions. These records define the installed configuration and support later troubleshooting, replacement, and recommissioning.

Related Products

Related Fume Hood Controllers

Use the integrated fume hood controller with VAV actuator when one controller-actuator package should serve rotary or linear airflow-control hardware. The fume hood face velocity controller is the closer alternative for direct velocity feedback with an integrated actuator, while the sash position fume hood controller is intended for resistive position demand with an integrated actuator. Compare control input, actuator architecture, supplied scope, wiring, and commissioning responsibility before selecting among them.

Related VAV Airflow-Control Devices

Pair the controller with a project-matched VAV butterfly damper or VAV Venturi air valve when that device, its actuator, airflow range, pressure condition, material, and connection have been selected separately. Browse Fume Hood Controllers to compare the controller architectures available for related hood projects.

Frequently Asked Questions

What does this fume hood VAV controller control?

The fume hood controller processes a project-defined demand signal and commands a separately selected actuator on a butterfly damper or Venturi air valve. Demand can be based on sash position or direct face-velocity input, while airflow-related differential-pressure feedback can support setup and monitoring. The controller also provides relay, panel, occupancy, temperature, and Modbus RTU interfaces for the configured sequence. It does not supply the fan energy, replace the hood, or prove containment without commissioning and the specified hood acceptance test.

Why is the actuator selected separately?

A separate actuator allows the project to match the actual airflow-control device, motion, load, travel, speed, mounting, signal, feedback, and fail position. This can suit a specified actuator brand, an existing damper or valve, a retrofit, or a combined assembly that cannot use an integrated controller-actuator. The flexibility is conditional: controller and actuator revisions must be checked electrically and mechanically, and the quotation must state whether the actuator, bracket, linkage, transformer, valve, and commissioning are included.

Can the controller use both sash-position and face-velocity inputs?

The product information supports sash-position demand and direct face-velocity control strategies. The project must define which strategy is used and provide the matching sensor, scaling, installation, setpoints, alarms, and commissioning procedure. Sash position describes opening geometry and is not a direct velocity measurement. A face-velocity sensor supplies a measured velocity signal but still depends on correct placement and calibration. The approved control narrative should explain whether airflow feedback is also used and how the selected input controls the external actuator.

Can it work with butterfly dampers and Venturi air valves?

Yes, XICHENG documentation identifies both butterfly damper and Venturi air valve applications. Compatibility is not automatic. Confirm the airflow-control device type, size, pressure condition, airflow range, material, connection, orientation, actuator mechanism, command, feedback, and measurement method. A Venturi name does not establish pressure-independent performance, and a butterfly damper name does not establish torque, leakage, or chemical resistance. Those values belong to the selected device and approved project schedule.

Can one controller operate multiple actuators?

The product information states that the controller can be used with multiple actuators on a combined airflow-control device. It does not publish one universal actuator count, total load, wiring arrangement, or synchronization method. A multi-actuator project must define the number of devices, power distribution, command distribution, feedback, travel matching, mechanical linkage, normal and fail positions, and response to one actuator failing. The final arrangement should appear on the approved wiring and control drawings and be verified during commissioning.

What must be checked before selecting the external actuator?

Check power, load, command and feedback ranges, common reference, isolation, rotary or linear motion, torque or thrust, travel, operating speed, direction, mounting, linkage, normal position, fail position, environmental exposure, and compatibility with the damper or valve. Also confirm whether the chosen controller revision uses voltage or current signaling. Signal compatibility alone is not enough: an actuator can accept the command and still be unsuitable for the required mechanical load, response, or failure sequence.

What do the differential-pressure and airflow-feedback functions do?

The controller uses a pressure-related measurement and configurable coefficient to support airflow calculation, feedback, setup, or monitoring for the installed arrangement. The coefficient must correspond to the airflow pickup, tubing, geometry, and field reference measurement. It is not a universal factory value. Commissioning should verify zero, tubing, direction, coefficient, reported airflow, and comparison with a suitable reference across the required operating states. Controller airflow feedback does not replace the final face-velocity or containment acceptance procedure.

What information is required for a project-ready quotation?

Send the hood and sash arrangement, opening dimensions, control mode, target face velocity, minimum through emergency exhaust conditions, airflow measurement method, damper or valve type and size, external actuator data, sensor package, power, analog and relay requirements, local panel, occupancy and temperature functions, Modbus point list, alarm and failure sequence, quantity, destination, and installation / commissioning responsibilities. The documented configuration should identify the controller revision, supplied components, I/O schedule, coordination requirements, documents, open items, and pricing.

Contact the Xicheng Engineering Team Today.

Send the hood and sash drawings, selected control mode, target face velocity and exhaust states, airflow-control device, external actuator data, sensor and panel requirements, I/O and BMS point list, alarm / failure sequence, quantity, and destination. These inputs support a controller configuration with documented supplied scope, technical schedule, outstanding confirmations, and commercial quotation.

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