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Frequently Asked Questions

We get a lot of questions about our airflow control products and our airflow measurement products. Please click a section below to see answers to the most common questions. If you need additional information, kindly contact us so that we may help you further.

  • AccuValve®

    • Why is a low pressure drop airflow valve important to me?

      A low pressure drop airflow valve can mean significant savings in operating costs over the life of the building. Using an airflow‐based valve instead of a mechanical pressure‐based valve can reduce duct static pressures by greater than 1.0" wc. This will result in fans running at lower brake horsepower and can mean savings of over $425,000.00 over a 20-year life of a building with 100,000 CFM of exhaust.
    • It's the 21st century – why would I want to use a mechanical pressure‐based valve in a critical environment application like a laboratory?

      The short answer is that there is no longer a good reason to use a 40‐year‐old mechanical design like a venturi valve with higher operating pressure requirements in your critical environment application.

      When VAV control of laboratories was first being installed, a mechanical device such as a venturi valve had advantages over closed loop control due to limitations of airflow sensing and the high cost of digital controls with the required scan rates to accomplish the speed of response required for this application.

      As with any industry many improvements have been made which has rendered mechanical open loop control an outdated method of control of a critical environment system. Some of these improvements are:

      Airflow Sensing – Venturi suppliers state that airflow measurement is not reliable or that it does not have the turndown required in a laboratory environment. While 25 years ago with only pitot and orifice plates available this had some validity, however the introduction of digital vortex shedding airflow sensors has eliminated this concern. Offering high accuracy, large turndowns and resistance to harsh environments, the vortex shedding airflow sensor is ideally suited for critical airflow control applications.

      Speed of Response – One positive of an open loop mechanical system was the high speed of response and 25 years ago it could not be matched by the digital controllers in a cost‐effective way. With the ever‐improving speed and lower cost of microprocessors this has also become a nonissue for closed loop systems which now offer superior performance and reliability to a mechanical pressure independent system.

      Nonlinear Damper– 25 years ago, the venturi was compared to a single blade damper. The single blade damper has a very limited turndown because of the inherent nonlinear action of the device. In 2006 the AccuValve was introduced which by using a dual chamber system with linearizing linkage it eliminated the hunting associated with a single blade damper allowing for much faster control action which is stable over a much wider range.
    • Why does the AccuValve operate at significantly lower duct pressures than a venturi valve?

      The AccuValve was designed as an airflow‐based control valve whereas the venturi valve is a mechanical pressure‐based airflow valve. The AccuValve measures actual airflow, thereby not having a requirement for duct pressure to operate. The venturi valve requires fan horsepower to "power" the mechanical spring and cone assembly.
    • What is the difference between a pressure‐based valve and airflow‐based valve?

      An airflow‐based valve such as an AccuValve does not require pressure in the system to operate. Instead it measures airflow directly and will drive the valve blades to achieve the required airflow regardless of the pressure in the system. In the event there is not sufficient pressure in the duct to achieve the required airflow it will read low airflow and an alarm will occur. The AccuValve is specified with a recommended maximum pressure drop of 0.3" for energy efficiency with the most energy efficient design between 0.1” and 0.2". The AccuValve provides control up to a maximum pressure drop of 0.45" when required.

      A pressure‐based airflow valve like a venturi requires pressure in the duct to operate. The mechanical system of cone, spring and slide bearings requires pressure in the ductwork to achieve its pressure independence. This results in using the fan brake horsepower to create the pressure independence.

      For example: A venturi is specified to operate between 0.6" to 3.0" wc. Venturi airflow valve manufacturers offer a lower pressure alternative 0.3” to 3.0” wc, but beware that to do so, the calibration of the spring changes thereby reducing the overall airflow range of the valve. This does not mean that it has a 0.3" or 0.6" pressure drop – instead it means that it requires a minimum pressure of 0.3" or 0.6" to operate. A venturi valve based "system" typically requires 1.5" to 2.0" of system pressure to insure its pressure independence.
    • I am controlling airflow, so why wouldn't I want to measure airflow?

      A very good question. We have always believed that if a parameter is important you should measure it. Over thirty years ago, when laboratory VAV controls were in their infancy, the airflow technology to reliably measure CFM in the harsh environments of laboratories were limited and expensive. Vortex shedding airflow measurement overcame the technical as well as the cost issues and there is no longer a reason not to measure airflow. It is by far the safest way to control airflow in any critical environment. Bottom line – to control temperature, you measure temperature; to control humidity, you measure humidity, therefore we feel it is important to measure airflow, which of course is the most critical parameter.
    • Why is it important to an owner to have Demand Based Static Pressure Reset Control in labs?

      Laboratories are generally the largest users of energy in any facility. Whether in a pharmaceutical research facility or a university research facility, laboratories use much larger amounts of energy than other operations. The industry has looked at ways to save on energy use by using VAV fume hood control systems as well as low flow fume hoods. These systems took a big bite out of energy use in labs. In continuing efforts to reduce energy costs and make buildings “greener” and sustainable, I2SL (formerly Labs21) has recommended reducing the static pressure drop of the devices in the airstream for both supply and exhaust systems in labs. ASHRAE Standard 90.1.‐6.5.3.2.3 addresses this issue to which the AccuValve design has incorporated its capabilities. Demand Based Static Pressure Reset Control (DBSPRC) offers dramatic savings in operating cost by minimizing the static pressure in the duct thereby allowing the supply and exhaust fans to operate at lower brake horsepower. To utilize DBSPRC the airflow valve must incorporate airflow measurement and closed loop control. Through the measurement of true airflow, the valve will modulate to the proper airflow volume. This will occur regardless of the static pressure in the duct. Information on the valve position will then be communicated to the Building Management System which will use that information to reset the static pressure in the duct to the minimum setpoint possible to maximize energy savings. An open loop mechanical venturi valve is not acceptable because it relies on a calibrated spring and plunger which only drives to a specific valve position and relies on the spring to compensate for pressure changes. Therefore, valve position is not indicative of required static pressure in the system and a venturi valve cannot be used for DBSPRC.
    • Has the AccuValve been recognized within the industry with any special awards?

      Yes, the AccuValve has been awarded "Winner" of the ASHRAE AHR Innovation Award for value, impact to the industry and application two times. First for the valve itself and again for the fume hood control system incorporating the Insight user interface. The AccuValve was designed to be a sustainable product from its inception. Its innovative features and benefits pulled the industry forward into the 21st century with a product that's designed for ease of layout, installation and operation with no recalibration and maintenance requirements.
    • Does the AccuValve require straight runs before and after the airflow control valve to properly measure airflow?

      No. The AccuValve does not require any additional straight duct run either before or after the airflow valve to measure airflow. The AccuValve incorporates a compression section in the inlet of the valve producing a uniform velocity profile for the airflow sensors without the need for straight duct into or out of the valve. Therefore, if needed, the AccuValve can also be mounted where there is no straight run available and meet the specified accuracy for airflow measurement.
    • Can the AccuValve be mounted in any position or is it required to be ordered and mounted in a specific horizontal or vertical arrangement as is required for a venturi airflow valve?

      The AccuValve can be mounted in any position on a 360° plane. Since it directly measures airflow and is not factory calibrated with a mechanical cone/spring arrangement (such as a venturi valve), all valves can easily be installed in any orientation as required by the project. All venturi valves require the valve to be ordered and installed in an exact vertical or horizontal arrangement to meet the factory mechanical calibration specifications.
    • Does the actuator/controller require specific installation to ensure operation?

      No. Unlike the venturi valve, the AccuValve can be installed with the controls accessible from underneath (at 6:00 position).
    • Can the AccuValve be provided in 304SS and 316SS to match typical exhaust ductwork?

      Yes. The AccuValve housing material is designed to match the associated ductwork for corrosive applications.
    • Can the AccuValve be provided with Electronic Pressure Independence?

      Yes. The AccuValve AVC model is electronically pressure independent. The AVC is designed with an integral closed‐loop feedback controller. Airflow measurement through the vortex airflow sensor provides a digital signal to the controller which modulates the electric actuator to maintain desired airflow setpoint.
    • Is the AccuValve provided with BACnet MS/TP?

      Yes. The AccuValve model AVC is provided with onboard native BACnet. The AccuValve model AVT offers an optional BACnet card.
  • AVC Fume Hood Control System

    • Does the AVC Fume Hood Control System provide independent control of the fume hood airflow volume?

      Yes. The award‐winning Accutrol AVC Fume Hood Control System provides a safe, energy‐efficient, cost‐effective independent fume hood control package. The system is configured to control VAV fume hood face velocity based upon open sash area. Alarms can be field configured to indicate a variety of fault conditions to further suit your facility’s specific needs. Importantly, your cost of ownership is reduced, and everyday operations simplified.
    • Does the AVC Fume Hood Control System directly measure airflow for true airflow feedback to the Laboratory Airflow Control System or is it metered?

      Yes. The Accutrol AVC Fume Hood Control System directly measures airflow through the integral digital vortex airflow sensor provided within the AccuValve.
    • Does the AVC Fume Hood Control System operate with different types of fume hoods (e.g.: Conventional VAV, High Performance, etc.)?

      Yes. The Accutrol AVC Fume Hood Control System can be configured to operate with any type of VAV fume hood on the market whether it be a conventional or high performance (low‐flow) design.

      The award‐winning Accutrol AVC Fume Hood Control System with free downloadable Insight software provides an unprecedented evolution in fume hood control technology. It significantly simplifies the start‐up, operation and modification for VAV fume hoods. The Accutrol AVC Fume Hood Control System combines the award‐winning design of the low pressure drop AccuValve® Airflow Control Valve with a “smart” fume hood display and a powerful and intuitive user interface. This innovative combination allows owners to easily set up and change the fume hood configuration without complicated manuals.
    • Is the Accutrol Fume Hood Airflow Controller integral to the Airflow Valve or provided separately for field installation?

      The Accutrol AVC Fume Hood Control System is integral to the AccuValve airflow valve. This creates a lower installed cost by saving installation time and wiring in the field. It is comprised of the AccuValve with an integral airflow measurement and control system, which includes a “smart” display mounted on the front of the fume hood. This unique measurement and control system, referred to as ePI®, provides pressure‐independent performance using sophisticated smart electronics rather than complex mechanical components in the air stream.
    • Is the Accutrol AVC Fume Hood Control System native BACnet MS/TP?

      Yes. The Accutrol AVC Fume Hood Control System is native BACnet MS/TP. The AVC controller uses the BACnet MS/TP (Master‐Slave/Token Passing) protocol which is a type of MAC layer implemented using the EIA‐485 signaling standard. The AVC AccuValve supports a collection of BACnet‐visible objects for Read, Write and Command.
    • Does the AVC Fume Hood Control System utilize a PC based system for configuration?

      Yes. The Accutrol AVC Fume Hood Control System utilizes a PC based system. When used with the standard AFC display and the free Accutrol Insight UI software, any Windows based laptop computer can be used to configure the controls to meet the needs of your fume hood. The Insight dashboard offers a wealth of information on the operation of the controls in a simple to understand user‐friendly format showing airflow measurement and setpoint in analog, digital and trending formats. The trending graph is extremely useful for tuning the control loop for your individual fume hood requirements.
    • How does a PC Based User Interface System differ from a menu‐based system?

      The Accutrol PC based system is an intuitive graphical user interface in simple to understand format from any Windows based laptop computer. Menu‐based systems require you to scroll through a large decision tree for configuration selections and do not provide any graphical based user interface.
    • What are some of the benefits of a PC Based User Interface System?

      A PC‐based User Interface System allows owners to easily set up and change the fume hood configuration without complicated manuals. Operation of the fume hood control is demystified in a simple to understand format showing airflow measurement and setpoint in analog, digital and trending formats. This enables owners to take charge of their system eliminating the need for costly local support.
    • Has the AVC Fume Hood Control System been professionally recognized within the industry?

      Yes. The AVC Fume Hood Control System is Accutrol’s second AHR Innovation Award winner in the Building Automation category.
  • Airflow Measurement Devices (VorTekG3)

    • Does the Accutrol VorTekG3 product line directly measure airflow?

      Yes. The VorTekG3 airflow measuring device utilizes vortex shedding technology. By utilizing vortex shedding technology, the shedder mounted in the air stream creates pressure pulses, which are converted to an electronic frequency. This electronic frequency is directly proportional to the airflow velocity and remains linear. That is why the VorTekG3 can maintain high accuracy over a very large range.
    • How does Digital Airflow Sensing differ from other technologies?

      One of the many advantages of vortex shedding is that the sensing is not amplitude based and cannot drift over time. Therefore, no recalibration is required – ever. Other airflow sensors rely on an amplitude measurement device, which is susceptible to inaccuracies and drift. Pitot and orifice sensors rely on differential pressure transmitters, which require periodic calibration. Thermal airflow sensors use thermistors, which will drift over time and must be matched to the electronics.

      The VorTekG3 is the only airflow measurement technology that is linear. The inherent physics of vortex shedding is a linear relationship between frequency and air velocity. That means that as air velocity changes, the frequency of the pulses changes in a linear manner. This eliminates the need for complicated curve matching associated with thermal devices.
    • What is the benefit of modular design?

      The VorTekG3 incorporates a unique, modular design concept. This enables you to order only the functions that are required for a specific application, eliminating the need to pay for features that are not required. Instead of multiple electronics platforms for different applications or "series" of models, the VorTekG3 simplifies user selection by utilizing a single electronics platform that can be used from a base of one sensing point up to sixteen sensing points. Any unit can be easily changed in the field to add sensors or reconfigure the range using the free Accutrol Insight graphical software.
    • Is the Accutrol VorTekG3 contamination resistant?

      Yes. Vortex sensors are contamination resistant since the sensing ports are on the downstream side of the sensor. This puts them out of the path of contaminants, so the “sensing side” of the device remains clean. Other airflow measurement technologies, such as thermal dispersion, are severely affected by contaminants in the air stream. As a thermistor gets coated with dust or dirt, the thermal transfer is impacted, seriously affecting the accuracy of the device.
    • Does the VorTekG3 product line offer BACnet MS/TP as an option?

      Yes. BACnet MS/TP can be ordered as an option. This option can be provided at time of order or added in the field at a later date.
    • Can you interface to the VorTekG3 with Accutrol's award‐winning Insight graphical interface software?

      Yes. The innovative design of the VorTekG3 incorporates the use of the free Accutrol Insight graphical user software. Gone is the frustration of older style alphanumeric displays and pushbuttons with a large decision tree user manual. The Insight software provides simple intuitive access to the configuration of the transmitter for different applications. The software connects to the VorTekG3 through a standard USB connection providing quick and easy access for the following:

      BAS – Allows simple field changes to the transmitter range, duct area.

      Commissioning – Allows simple adjustment for unusual airflow profiles due to duct conditions.

      Owner – Can make changes to ranges, number of sensors, etc. as the system requirements change.
    • Can the transmitter be configured in either Imperial or Metric units for velocity, volume and area of measurement, and will it carry through to BACnet when required?

      Yes.