18
AIRFLOW
AIRFLOW
RETURN
BAROMETRIC
BYPASS
HORIZONTAL APPLICATION
SHEET METAL
PIPE
SUPPLY
PLENUM
A/C UNIT
OR
FURNACE
A/C UNIT
OR
FURNACE
RETURN
AIR
PLATFORM
BAROMETRIC
BYPASS
RETURN AIR GRILLE
AIRFLOW
SUPPLY
PLENUM
VERTICAL APPLICATION
ROOFTOP INSTALLATION
Down Discharge Application
A/C UNIT
OR
FURNACE
BAROMETRIC
BYPASS
AIRFLOW
SHEET METAL
PIPE
RETURN
PLENUM
SUPPLY
PLENUM
ROOF LINE
OPEN RETURN PLENUM BYPASS APPLICATION
RETURN AIR
GRILLE
AIR CONDITIONING
UNIT
SUPPLY
DUCT
BYPASS DAMPER
To prevent bypass air from
flowing out the
return grill,
use a short open ended
return air plenum to
connect the bypass
damper to the unit.
BYPASS DAMPERS- BAROMETRIC
INSTALLATION
The round barometric bypass damper can be installed in any
position. This damper is factory set for horizontal installation and
can be
field modified for vertical installation. Do not run speed
screws into damper housing. Screws may interfere with damper
travel. Make sure counterweight is not obstructed in any way.
a) Install the bypass damper between the supply and return
plenums of the unit. It must be the
first
tap off the supply plenum.
b) Be sure the air
flows
through the damper in the proper direc-
tion as indicated by the arrow on the damper.
Airflow
is
always from supply to return plenum. Be certain the
damper shaft is horizontal.
c) Loosen counter weight with allen wrench.
d) Loosen lever arm from damper shaft and allow to hang
straight down.
e) Fully close damper by grabbing damper shaft on side
attached to lever arm and turning clockwise until it stops.
f) While holding the damper fully closed, rotate the lever arm
a little to the right (facing the damper) and then screw in
to tighten to the damper shaft. Then tighten lock nut.
g) Be sure the damper is being held closed by the counter
weight. Proceed to setup.
BAROMETRIC BYPASS SETUP
a) Turn off all thermostats.
b) Turn on Controller and set fan switch to “ON” position.
Allow fan to run for 5 minutes to equalize pressure.Then
make sure all dampers are open by checking for air
flow
out of each damper.
c) By moving counter weight up or down the lever arm,
adjust it so the damper just wants to start opening.
d) If the damper cannot be held closed with the counter
weight all the way to the bottom of the lever arm, then
hold the damper shaft, loosen the lever arm from the
damper shaft, and rotate the lever arm farther to the
right and retighten. Repeat Step C.
e) The barometric bypass damper is now calibrated.
BAROMETRIC BYPASS STARTUP TEST
a) Have at least half of the zones call for either heating or
cooling.
b) Check to be sure the calling zone dampers are open,
(air i
s flowing).
c) Verify the bypass damper is open. Note, the damper
may not fully open.
d) If the open zones are not noisy, the bypass damper is
set.
