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AIR FLOW, AIR VELOCITY, ACPH, AHU CAPACITY

Air Changes per Hour

AIR VELOCITY AND ACPH OF ROOM OR AREA
 

Procedure to be followed:

Air Velocity Measurement and Calculation of Air Changes:

Objective:

To demonstrate that the air system is balanced and capable of delivering air velocities and providing number of air changes per hour in the respective rooms as per requirement.

Equipment to be used:

Hotwire Anemometer or capture Hood

Pre Requisite:

Air Volumes through supply and return grills and filters should be adjusted as per the design requirement of Air Change Rate and Differential Pressure.

Test Method:

Ensure that the Supply blower of the AHU is "ON" prior to the start of the observations. For compliance of air change rate, velocity to be measured at 5 different locations to below the each terminal or Grill (Four Corners and center) with the help of calibrated Anemometer.

Calculate the average velocity of the air coming from Plenum HEPA filter / supply air grill. Calculate the airflow by multiplying the average velocity with the effective filter area.

Air flow = Average Velocity x Surface Area of the filter

= Ft / Minute X Ft 2

= Ft 3 / Minute or CFM

Calculate the total airflow from all the Terminal Filter / Supply Air Grill in the room and add values to get the total airflow in the room (CFM).

                        Calculate the number of air changes per hour in the room by using the formula:

                       Air Changes / hour = Total air flow in the room (CFM) x 60

Room Volume (Ft 3) 

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