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7. BALANCING THE UNIT
7.1 WHAT YOU NEED TO BALANCE THE UNIT
• A magnehelic gauge capable of measuring 0 to 1 inch of water (0 to 249 Pa) and 2 plastic tubes.
• The balancing chart of the unit.
7.2 PRELIMINARY STAGES TO BALANCE THE UNIT
• Seal all the unit ductwork with tape. Close all windows and doors.
• Turn off all exhaust devices such as range hood, dryer and bathroom fans.
• Make sure the balancing dampers are fully open by setting both damper balancing tools completely vertical.
• Make sure all filters are clean (if it is not the first time the unit is balanced).
7.3 BALANCING PROCEDURE
1. Set the unit to high speed.
NOTE: Make sure that the furnace/air handler blower is ON if the installation is in any way connected to the ductwork of the cold air
return. If not, leave furnace/air handler blower OFF. If the outdoor temperature is below 0°C/32°F, make sure the unit is not
running in defrost while balancing. (By waiting 10 minutes after plugging the unit in, you are assured that the unit is not in a
defrost cycle.)
2. Place the magnehelic gauge on a level surface and adjust it to zero.
3. Connect tubing from gauge to EXHAUST air flow pressure taps (the ones with
arrows, see insets in illustration at right).
Be sure to connect the tubes to their appropriate high/low fittings. If the gauge
drops below zero, reverse the tubing connections.
4. Note the CFM value from balancing chart on unit.
5. Repeat steps 3 and 4, but to FRESH air flow pressure taps.
6. Match highest CFM value to lowest by adjusting the balancing damper
corresponding to the highest value.
See example below:
In that case, there is 150 CFM in FRESH air and 125 CFM in EXHAUST air. Then, adjust (close) the FRESH air balancing damper
until the FRESH air flow matchs the EXHAUST air flow: 125 CFM (0.67 in. w.g.) with magnehelic gauge connected to FRESH air
flow pressure taps).
7. Secure both dampers in place with a fastening screw (included).
8. Write the required air flow information on a label and affix it near the unit for future reference (date, maximum speed air flows, your
name, phone number and business address).
NOTES: 1. Use conversion chart provided with the unit to convert magnehelic gauge readings to equivalent cfm values.
2. The unit is considered balanced even if there is a difference of ±10 cfm (or ± 5 l/s or 17 m³/h) between the two air flows.
VP0009
VR0029
DAMPER
BALANCING
TOOL
VP0017
STALE AIR FLOW
FRESH AIR FLOW
FLOW FRESH EXHAUST
CFM IN. W.G. IN. W.G.
120 0.71 0.73
125
0.67 0.70
130 0.63 0.67
135 0.59 0.64
140 0.55 0.61
145 0.51 0.58
150 0.47 0.55
EXHAUST READING VALUES
FRESH READING VALUES
VR0030
FASTENING SCREW
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