9
AIRFLOW BALANCING
1
For this flow measuring
station, cut the duct and
place the flow measuring
station between each section
of duct. Make sure that the
flow measuring station’s air
direction arrow points in the
direction of the airflow.
Secure the flow measuring
station with duct tape.
2
Before taking the
reading, make sure
that the magnehelic
gauge is level and at
0. Refer to the flow
measuring station’s
chart to determine
your unit’s airflow
velocity.
3
Adjust the “Supply Air
Out” damper until you
reach the desired
velocity. Follow the
previous steps to adjust
the “Exhaust Air Out”
damper, if needed.
B
Measure
here
Measure
here
12”
(300 mm)
12”
(300 mm)
• To avoid airflow
turbulence and
incorrect readings, the
airflow velocity should
be measured on steel
ducting a minimum of
12” (300 mm) from
the unit or elbow and
before any transition.
The following procedure is designed for measuring airflow and balancing
an HRV based ventilation system.
Step 1:
Prepare the house
• Air/vapor barriers must be complete.
• Fireplace dampers, windows and doors closed.
• Clothes dryers and other large exhaust devices must be off.
Step 2:
Prepare the system
• Ventilation system must be complete, including grilles and registers.
• Check that filters are installed and clean.
• All system dampers set to operating positions (fully open for
new installations.
• Check that intake and exhaust hoods are clear.
• Check that the HRV drain trap is full of water.
• In cold weather, check that HRV is defrosted and not in defrost mode.
• Turn HRV (fans) on high speed.
Step 3
: Taking measurements
• Ensure measuring gauge is level and secure. Magnehelic or slope
manometer cannot be hand held.
• “Zero” gauge as required.
• Connect hoses to high and low ports of gauge and MBS. High to
high and low to low.
• Read pressure from gauge and convert it to cfm using the chart for
the unit’s MBS. Record reading.
• This process must be done twice, once for the supply duct system
and once for the exhaust duct system.
Step 4:
Balancing the airflow
Both the supply and exhaust measurements taken in step 3 must be
greater than or equal to the Total Ventilation Capacity. An HRV is
deemed balanced if the supply and exhaust flow are or- 10% of
each other.
• From the chart on
the MBS, determine the
pressure reading which
corresponds to the
ventilation rate required
(TVC). With the
measuring gauge
attached to the MBS,
slowly close volume
damper until gauge reads
the correct pressure.
• Lock volume damper in position.
• Repeat the above procedure for the second duct system. It does
not matter whether the supply or exhaust is adjusted first.
AIRFLOW STATION (GRID) METHOD
*
Fantech’s superior design and use of EBM motors results in a steep fan curve that usually does not require balancing.
Commissioning the system after installation is recommended which includes confirming the proper operation of the system and
how it interacts with other components within the home.
HIGH
LOW
LOW
HIGH
SUPPLY
EXHAUST
Measuring and Balancing Airflow with a Measurement and Balancing System
