# Air Pressure Measurement

Air pressure measurement as related to atmospheric pressure compared to buildings is done using specific instrumentation for specific tests. Calculations are done using no more than high school mathematics. Measuring air flow in buildings takes some training and is usually done by a technician trained in air balance techniques.

Also explains hpw to measure pressure with pressure sensors.

The air balance technician also makes air flow adjustments.

These air flow adjustments are commonly known as air balancing.

Air pressure measurement may entail:

Adjusting motor pulleys to increase or decrease fan speeds. When it is noted that air flow as produced by a supply, return or exhaust fan is below design parameters adjustments will have to be made.

Whether fan motors and blowers can be increased in speed is dependent on the horsepower (HP) of the motor that is in place. If there is sufficient amperage draw available on the motor it may be sped proportionately.

To increase or decrease fan or blower speed the fan pulleys will have to be changed. To decrease fan speed a smaller outside diameter motor pulley must be installed. This will result in the motor amperage being decreased. To increase fan speed a larger outside diameter motor pulley must be installed. This will result in the motor amperage being increased.

It is a direct relation between fan speed and fan air volume. If you increase the fan speed by 10% you will increase the air volume by 10%. If you decrease the fan speed by 10% you will decrease the air volume by 10 %.

However this is not true of motor current draw. If you increase fan speed by 10% you will increase motor current draw by close to 30%. Before increasing pulley size you must be certain that the HP of the motor is great enough. If it is not, it will then require that the motor be replaced with one of a greater HP and current draw capability.

Technicians after setting the correct air system air volume are then required t adjust zone balance dampers to increase or decrease zone supply and return air to meet design criteria.

Technicians after setting the correct zone supply air volumes then adjust individual supply air diffusers balance dampers to increase or decrease supply air flow to individual areas or offices.

When the supply air volumes are correct the technician must adjust individual return air grille balance dampers to increase or decrease return air flow to individual areas or offices. When the supply and return air volumes are correct the technician is required to adjust individual exhaust air grille balance dampers to increase or decrease exhaust air flow to individual areas or offices.

At the end of the air pressure measurement and air balance a report must be compiled detailing all fan and diffuser design and actual balanced conditions.

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