The following is the general procedures we use in the testing and balancing of most projects. The project specifications are the guidelines for test data and measurement procedures on all projects.  All test and balance procedures are detailed in the “NEBB Procedural Standards for Testing, Adjusting and Balancing of Environmental Systems, Seventh Edition 2005”.  The following was selected from that manual and applies to most projects.





 1. List and identify size, type and manufacturer of all diffusers, grilles, registers and all tested equipment.  Use equipment manufacturer’s ratings to make any required calcula   tions.


 2. Identify each grille, diffuser and register with a number that is referenced on an accompanying sketch.


 3. If the system is “variable air volume” (VAV), adjust all the terminal unit flow rate regulators to the required minimum and maximum CFM while monitoring and recording duct static pressure.  If the system is constant volume (CV), proceed to step #5.


 4. Set enough VAV’s to maximum CFM and minimum CFM to equal the rated cooling coil CFM.


 5. Test and adjust system for design percentage of outside air.


 6. Test and record motor load amperes.


 7. Make pitot tube traverse of main supply ducts, where possible, to determine total supply CFM.


 8. Test and adjust blower RPM as necessary to achieve design CFM.


 9. If the system is constant volume, adjust all zones to proper design CFM, supply and re  turn.


10. Test and adjust each diffuser, register and grille to within plus or minus 10% of design requirements.  Care should be taken to minimize drafts whenever possible.


11. Test and record re-circulated air flow rate (CFM).


12. Test and record system static pressures, suction and discharge.


13. Temporarily set water flows and temperatures to design conditions for temperature tests.


14. Test and record entering air temperatures.  (D.B. heating and cooling)


15. Test and record entering air temperatures.  (W.B. cooling)


16. Test and record leaving air temperatures.   (D.B. heating and cooling)


17. Test and record leaving air temperatures.   (W.B. cooling)


18. List test data for all diffusers, grilles and registers, including design CFM and test resultant CFM after adjustment.  When “Direct Reading Flow Hoods” cannot be used, ap   plicable “Ak” factor, design velocity and test resultant velocity shall be shown.


19. Test and record required information pertaining to other equipment included in the HVAC contract such as electric duct heaters, exhaust fans, computer room units, etc.


20. The Mechanical Contractor shall be responsible for making any changes in the pulleys, belts and dampers or adding dampers as recommended by the air balance agency to achieve correct air balance.



“NEBB Procedural Standards”