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BACNET™ MOTORIZED VAV DIFFUSER
SYSTEM AIR BALANCING
VAV systems are balanced for design air volume at maximum air flow and systems using Therma-Fuser VAV diffusers are no
exception. When all the Therma-Fuser diffusers are set for maximum airflow by fully opening them, the system is really a constant
air volume system and is balanced as a constant volume system. Balancing dampers are best located at the takeoff before the run
out to the diffuser.
1.
Prepare system for balancing. (Make necessary checks for diversity, fan capacities, fan rotation, minimum outside air
requirements, duct leaks and static pressure controller design setting. Set outside air control damper for minimum air and
return air control damper for maximum air.)
2.
Open EF-B diffusers for balancing.
a. The EF-B-M is shipped in the open position and will remain open until power is connected.
or
b. Set the value of the Object analog_value_25 (iOverride) to '1'. Allow 1-2 minutes for all diffusers to open fully.
3.
Start fans, adjust system for 100% air flow and make system checks. (Measure static pressure across filters and coils and at
sensor for static pressure controller. Measure supply, return and branch duct air flow.)
4.
Measure air flow from each EF-B diffuser and adjust the damper at the duct takeoff to obtain maximum design air flow. Air
flow measurement may be with a direct reading diffuser balancing hood or air velocity meter. In either case, measurements are
made with all appearance panels in place. This is because the appearance panel affects pressure drop through the diffuser.
When velocity meter is used to measure the discharge velocity, the velocity is measured at the top edge of the housing.
5.
When balancing is complete, return each model EF-B diffuser to normal operation by setting the value of the Object analog_
value_25 (iOverride) to '0'.
NOTE:
Diffuser noise is caused by higher velocity air through the diffuser which is caused by a high static pressure. Acutherm
recommends a static pressure no higher than 0.25"wg / 62Pa at the inlet to the diffuser. Some system designers may accept
higher noise levels and opt for a higher static pressure. Care should be taken not to exceed the design maximum static pressure at
the takeoff to the first EF-B diffuser after the static pressure control or, if none, after the fan.
acutherm.com | BACNET™ MOTORIZED VAV DIFFUSER - Manual
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