27
BALANCING PROCEDURE
1. Set the unit to high speed.
Make sure that the furnace blower is ON if the installation is in any way connected to the ductwork of
the cold air return. If not, leave furnace blower OFF. If the outside 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 flow collar (or flow measuring station) in exhaust
air stream at location A. Be sure to connect the tubes to their appropriate
high/low
fittings. If the gauge drops below zero, reverse the tubing connections.
NOTE: It is suggested to start with the exhaust air flow reading because the
exhaust has typically more restriction than the fresh air, especially in
cases of fully ducted installations and exhaust ducted installation. Place
the magnehelic gauge upright and level. Record the readings.
4. Move tubing to FRESH air flow on the other side of the unit (location B) and
note readings.
Adjust the fresh air balancing damper F until the reading at B is approximately the
same as the reading at A. If the reading at B is less than the reading at A, then
go back and adjust the exhaust balancing damper
G to equal the fresh air flow.
5. Secure both dampers in place with tape or with a fastening screw.
6. If you are using flow collars, remove them, reconnect the duct and seal with duct tape. If you are using
“Flow Measuring Stations”, remove them and seal the holes with duct tape. Write the required air flow
information on a label and stick it near the unit for future reference (date, maximum speed air flows, your
name, phone number and business address).
NOTES: Most flow collar kits provide a conversion chart located on the collar which enables you to convert
magnehelic gauge readings to equivalent cfm values.
The unit is considered balanced even if there is a difference of +/- 10 cfm (+/- 0.015 inch w.g.)
between the two air flow readings.
If you are only using one flow collar or one “Flow Measuring Station”, then, after completing the first
reading, transfer this measuring device to the other side of the unit and take the second reading.
VD0052
10.0
Air Flow Balancing (cont’d)
LOW HIGH
FLOW
VP0004
F
G
LOW
H
IG
H
FLOW
VP0003
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