AFA4000/E VAV Airflow Controller / p.100
• Take extra time, at least 15 to 20 seconds, to wait for the airflow to settle before capturing
the airflow samples. This will minimize the chance of a calibration error due to turbulence
or fluctuations.
• Avoid movement in front of the fume cupboard whilst calibrating the monitor.
• The Low and High air samples must be at least 0.3 m/sec (60 fpm) apart to calibrate the
monitor. This is to avoid inaccuracy in the calibration due to insufficient difference between
the samples. The minimum difference can be changed in the Low High diff parameter in the
Cal Config menu.
• Do not use fully open and fully closed sash positions for the calibration points, the
recommended positions are normal operating height (e.g. 500 mm, 20”) for the first sample
and approximately half the sash opening (e.g. 250 mm, 10”) for the second sample.
• For the Low Air sample, open the sash to the max safe working opening when using a fume
cupboard with sliding sashes.
• For the Higher Air sample, close the sash to approximately 50% of the opening used for the
Lower Air sample. The sensor will detect if the Higher Air sample value is too close to the
Lower Air sample, and you will be asked to repeat the reading with a higher value. To do
this, close the sash slightly and repeat the sample. Do not close the sash below 150 mm.
• The face velocity readings on the open sash may vary at different points on the measuring
grid by up to 0.1 m/sec. This is acceptable, long as individual points are not below the
designated Low Air alarm point.
• The figure entered for the calibration point can be taken as the average value of all the
measuring grid readings or could be taken as the individual lowest point on the grid. This
low point is typically located in the centre of the bottom row. The low point is a suitable
convenient position to measure and for alarm testing.
• When calibrating the alarm, it is important to ensure that the ‘Vent kit’ is connected to the
SM7 sensor on the fume cupboard. When the vent kit is not connected to the sensor, the
sensor will not detect a change in the airflow during the calibration procedure and will
display Sensor Difference too low - Check sensor. This only applies during calibration.
• When the vent kit becomes disconnected following calibration the air flow across the
sensor will fall and the alarm will go into the ‘Air Fail’ condition.
• When calibrating the Controller for Dual Set point operation, bear in mind the accuracy at
both set points. The Low Air sample should be taken at the approximate Low set point
value (e.g. 0.3 m/sec) and the High Air sample should be taken at the approximate High Air
set point value (e.g. 0.6 m/sec) considering the min 0.3 m/sec difference required between
the calibration values.
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