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Chapter Overview
This chapter contains information
about the following:
— VAV air balancing
— VAV water balancing
28
Air Balancing and
Water Balancing
CHAPTER 6: AIR BALANCING & WATER BALANCING
Air Balancing
After the unit has been mounted and all
electrical and duct connections have
been made, the air distribution system
should be balanced. The proper variable
air volume balancing procedures
depend on the type of VAV system used
and the options specified on the
VariTrane unit. This section will cover
the basic balancing procedures and
calibrations needed to balance an air
distribution system using VariTrane
units. This section suggests only one
balancing procedure. Since there are
many possible air balancing proce-
dures, keep in mind that these proce-
dures are only suggestions.
Note: Before performing these balancing
procedures, the calibration command
should be initiated at least 15 minutes
prior to the balancing procedure.
1. System Checkout
— Check the VAV system installation for
conformity to design.
— Walk the entire system from air
handling equipment to the terminal unit
to determine variations of installation
from the plans.
— Check for inadvertent obstructions in
the ductwork (such as closed fire
dampers).
— Insure that any turning vanes, filters,
and dampers (both volume and fire) are
installed in the correct position.
— There should be a 1.5 duct diameter
long run of straight ducting into the
valve.
— Set the outside air dampers to their
minimum position.
— Start the supply and return air fan(s).
2.Before we can balance the system, we
need to ensure that there is enough
CFM for all zones.
A.Drive all VAV boxes MAX.
— Starting with each individual branch
duct, open all the VAV units in that
branch duct to the maximum cooling
position.
— This can be done using EveryWare by
giving each UCM a "Drive Max"
command or by rotating the Zone
sensor set point knob to the " * "
position, and hold the TOV ON button
for two seconds.
— The damper will remain at its maximum
set point until the zone sensor knob is
moved back into the normal operating
range.
B.Read airflow at the most remote unit.
— In most systems, this will be the VAV
unit located furthest from the fan.
— This will be the unit in the system that
will be critical from an air delivery
set point.
A.If airflow is not adequate, increase the
supply fan CFM to achieve adequate
airflow.
B.Make the required adjustments to
pulley sizes, motor sizes and electrical
connections to accommodate fan-
speed changes.
3.With all VAV boxes fully open, take a
measurement of the total CFM.
— CFM is determined by using this flow
signal and the chart on the side of the
unit (different size units have different
charts).
— If the CFM is at or above design, the
system can now be balanced. If the
measured CFM is below design, insure
the VariTrane unit is in full cooling
position.
— If the air delivery through this VariTrane
unit is still below the design
requirements, the supply fan rpm
should be increased until the correct
design airflow is obtained or the fan
reaches its maximum capacity.
— If after adjusting the fan to its maximum
capacity there is still a shortage of
airflow, shut off part of the system to
provide enough airflow to balance the
other part of the system. This can be
done using the "Override to
Unoccupied" command ("**") at the
zone sensor.
4.After determining that there is enough
CFM for all zones, drive all the VAV
boxes to MIN.
VAV-SVX01B-EN
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