Air & Water Balancing - A Key Part of Commissioning. Air
and water balancing is a method of regulating HVAC air supply, return, and
exhaust, or the flow of water through coils, to achieve a neutrally balanced, comfortably
conditioned commercial, institutional, or industrial building.
HVAC Testing, Adjusting and Balancing (TAB) are the three
major steps used to achieve proper operation of HVAC (heating, ventilation, and
air conditioning) systems. TAB usually refers to commercial building
construction and the specialized contractors who employ personnel that perform
this service.
In general, the TAB specialist performs air and hydronic
measurements on the HVAC systems and adjusts the flows as required to achieve
optimum performance of the building's environmental equipment. The balancing is
usually based upon the design flow values required by the Mechanical Engineer
for the project, and the TAB contractor submits a written report which
summarizes the testing and balancing and notes any deficiencies found during
the TAB work. Many times, facility managers will use a TAB contractor to assist
in identifying preexisting or common issues with a facility. While not
necessary to be a TAB contractor, many contractors tend to hold professional
air balancing certifications.
Testing
Testing is the use of specialized and calibrated instruments
to measure temperatures, pressures, rotational speeds, electrical
characteristics, velocities, and air and water quantities for an evaluation of
equipment and system performance.
Adjusting
Adjusting is the final set of balancing devices such as
dampers and valves, adjusting fan speeds and pump impeller sizes, in addition
to automatic control devices such as thermostats and pressure controllers to
achieve maximum specified system performance and efficiency during normal
operation.
Balancing
Balancing is the methodical regulation of system fluid flows
(air or water) using acceptable procedures to achieve the desired or specified
design airflow or water flow. When beginning the balance of a system, you must
locate the terminal with the least amount of flow regarding the engineer's
drawing. Once the "low" terminal has been located, you can then
proceed to adjust all other diffusers/grilles (air) or circuit balancing valves
(water) to proportionally match the original "low" terminal. There
must be at least one terminal that is wide open to achieve optimum efficiency.