MLM Airflow Measurement | rickardair

MLM Airflow Measurement

Rickard is proud to offer airflow sensing at the diffuser level. This technology measures total pressure and air volume allowing easy commissioning, the limiting of maximum diffuser volumes to meet a building’s design, integration with the building BMS, calculation of HVAC energy consumption per zone and aids troubleshooting of problem zones that are out of temperature control.

Rickard VAV Diffuser-Air Flow Measurement Module


It is now possible to commission the entire building electronically. Two modes namely a static and adaptive commissioning mode is available depending on preference. The static commissioning mode allows the user to set the diffuser to a fixed minimum and maximum damper position, based on the airflow delivered at a pressure that will be maintained during system operation. The adaptive commissioning mode allows the user to set the diffuser to a minimum and maximum airflow value. The diffuser will work to limit the minimum and maximum airflow delivered despite some fluctuations in diffuser neck total pressure. Both modes require a MCU to be connected to the diffuser network. When pressures rise too high, the diffuser will reduce the flow to the designed maximum flow therefore reducing energy consumption and preventing over-cooling or heating. The minimum flow position ensures that sufficient air is always delivered.


Airflow and Total Pressure can be viewed and monitored through the Rickard MLM software and BMS. Airflow measurement makes it easy to troubleshoot problem zones that are out of temperature control.

The MLM Airflow Sensor is a cartridge that has been developed to fit into the spigot of a diffuser.

The Airflow Sensor Neck option houses the airflow cross in a typical spigot configuration. This option requires a flex bend to ensure the entry conditions to the neck are correct.

Display of Airflow & Pressure on MLM Application


Each Airflow Device measures the flow through a Diffuser, accurate to within +/-10% of actual flow, when measuring total pressures between 10 and 100Pa. Please see recommended installation instructions to ensure sensing accuracy and repeatability.

Rickard airflow sensors are designed to be used in a typical field installation i.e. with flexible duct entering the diffuser from the side.

The Airflow Sensor Hard Bend option ensures entry conditions are always the same therefore ensuring the devices accuracy.

Since the angle and shape of the flex can effect the Airflow Sensor accuracy, every airflow sensor comes with a flex bend to ensure the shape of the flex entering the diffuser is always the same.

  1. The Airflow Sensor should be rotated on the diffuser neck so that the Flex Bend runs parallel to the entry orientation of the flex.

  2. The flex should lie squarely in the bracket of the flex bend.

  3. The flex should be extended as much as possible and not concertinaed in the bend. Use the fixing tie (not shown)included to ensure the flex remains in this position.

  4. Use the jubilee clip included to secure the flex to the Airflow Sensor neck to prevent leaks.

Extend Flex and Secure with wire fixing tie (not shown)


To calculate airflow Rickards airflow sensors measure the difference between pressure in the diffuser and pressure in the room. If pressure in the ceiling (room pressure sensor position) and pressure in the room is different, it is possible to offset this difference using the MLM software.


Rickard Airflow Sensors can be fitted to each diffuser for accurate airflow calculation (less than 10%) or to one diffuser per zone to calculate an indication of airflow at each diffuser in that zone (results will vary according to the variation in pressure between the master and slaves in that zone).


Neck total pressure in Pa or inWG
Airflow in l/s, cfm and cmh
Outputs are displayed on Rickards MLM Software and can also be communicated to the BacNet BMS.

  1. Position the diffuser in the ceiling grid so that the slot in the Airflow Sensor neck roughly faces the entry direction of the flex.
  2. Rotate the Airflow Sensor in the diffuser neck so the slot in the Airflow Sensor neck faces the entry direction of the flex. Use duct tape or aluminium tape to secure it in this position and to prevent leaks.
  3. Slide the flex over the Airflow Sensor neck.
  4. Detach the loose end of the jubilee strap from Flex Bend.
  5. Fit the foot of the Flex Bend into the slot provided in the Airflow Sensor neck.
  6. Thread the loose end of the jubilee strap around the flex, through the hole in the Flex Bend support and into the jubilee strap clip.
  7. Close the jubilee strap clip and tighten the strap so that the  flex is securely and squarely attached to the neck.
  8. Untie the ends of the fixing tie that is attached to the other Flex Bend support.
  9. Pull the flex tight to limit the concertina effect of the flex in the bend.
  10. Tighten the fixing tie around the flex to secure it in position.

Jubilee Strap

Airflow Sensor Neck


A Rickard Master Communications Unit (MCU) and Free MLM Software are required to calculate each diffusers Pressure and Flow. A BacNet MCU allows these parameters to be communicated to the BacNet BMS.


Compatible with Rickard VCD1, VSD1, VSW1 and VLN1 products.
Compatible with Rickards MLM Software and can also be communicated to the BMS.