How to do a proper air balancing
Updated: Apr 4, 2022
This is always a question when clients find that there is hot spots or cold spots after taken over a new premises.
For new building , usually it is equipped with VAV boxes to control airflow and temperature to each zone .
Steps Procedures Date 4.4.22
Step 1- Prepare the As-built drawing of the completed ACMV Project.
Step 2 - Tabulate all VAV boxes and diffuser design airflow to an air balancing blank report for recording purposes.
Step 3- Prepare all room's heat load calculations in order to calculate the design airflow.
Step 4 - Ensure all the rooms have doors and ceilings so that airflow can be accurately measured.
Step 5 - Ensure the site is clean.
Step 6- Ensure all existing temporary filters are removed.
Step 7- Ensure AHU runs full speed @ Hz (50 Hz).
Step 8 - Work with the Building management system (BMS) to change the existing airflow setting to a new design airflow setting. (Max & Min airflow)
Step 9- Ensure all VAV Box dampers are fully open by BMS or set each VAV Box thermostat to 15 DegC.
Step 10- Physically check that all VAV boxes are fully open from the actuator.
Step 11- Take all airflow of the diffusers to find out where most of the air goes.
Step 12- Adjust the splitter dampers along each branch duct to get the correct amount of air to each branch.
Step 13- If the airflow for the diffusers is higher at the end of the last diffuser, then, start adjusting the airflow from the last diffuser towards the first outlet.
Step 14- If the last diffuser does have not have enough airflow, then start adjusting from the first outlet to push the air towards the end of the last diffuser or branch.
Step 15- Double-check or take a sampling of the airflow from the diffuser once the particular branch is completed. Do a proportional air balancing for each branch.
Step 16- Adjust the airflow of each diffuser to the design airflow with a tolerance of +10% or -10%.
Step 17- After completion, check through all rooms to ensure the return air is enough, by checking the followings:
(i) We are able to breathe easily without any effort.
(ii) No noisy airflow from the diffusers.
(iii) No vibration of the ceiling or wall.
(iv) No extreme positive or negative air pressure so that the door can be easily
opened or closed.
(v) Check to ensure the rooms are able to have comfort even when there is strong sunshine that created extra heat load and adjust airflow if necessary.
Step 18- Check for any abnormal air noise and adjust the diffusers to reduce or increase air if necessary.
Step 19- Record all readings into the air balancing report.
Step 20- Update the ACMV drawing with the actual airflow.
Step 21- Put the VAV system to Auto mode after completion through BMS.
Step 22- Ensure after air balancing all VAV Thermostat Setpoint 23 DegC to 24 DegC
Step 23- Double Check with BMS the airflow reading that was taken