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BYPASS DAMPER – STATIC PRESSURE CONTROLLER
The Static Pressure Controller controls a standard medium pressure round damper (STMPD) or the heavy duty rectangular damper (STCD) by
maintaining constant static pressure in the duct downstream of the bypass takeoff. As the zone dampers close, the static pressure increases. When
this happens, the static pressure controller opens the bypass damper to bring the static pressure back to the setpoint.
STATIC PRESSURE CONTROLLER DESCRIPTION
A:
Mounting tabs.
B:
Supply air barb.
C:
Reference air, “LOW”, barb.
D: Diaphragm must be
mounted vertically.
E:
Pressure adjusting screw.
F:
Normally closed, N/C, terminal.
G:
Normally open, N/O, terminal.
H: Common, COM, terminal.
STATIC PRESSURE CONTROLLER INSTALLATION
a.
Select location for pressure sensor tube. Location should be in sup-
ply duct, downstream of bypass takeoff, upstream of any zone
dampers and perpendicular to the air flow.
b. Drill 5/16” hole at selected location for pressure sensor tube.
c.
Mount Static Pressure Controller near the drilled hole with the
diaphragm of the sensor vertical. The controller must be mounted
on a stable, non vibrating surface.
d. Attach 5/16” pressure sensor tube, supplied, to the barb of the Sta-
tic Pressure Controller located closest to the mounting tabs. The oth-
er barb, labeled “LOW”, is left open if the Controller is in the
conditioned building. If the Controller is located outside the build-
ing, another tube, not provided, must be connected between the
“LOW” barb and a location inside the building.
e.
Remove the terminal cover and wire as shown in the wiring
diagram.
f.
Reattach terminal cover. Installation is complete. Proceed to Static
Pressure Controller Setup.
STATIC PRESSURE CONTROLLER SETUP
Note:
24V ac may be read on both terminals (RO & RC to MC) due to
voltage bleeding thru the motor windings. Disconnect the RO or RC wire
to determine which wire is energizing the motor.
a. Ensure all dampers are open and blower is running on high speed.
b. Verify bypass damper is
Closed
.
Bypass dampers using a square
motor have a grey release lever on the bottom/side of the damper
(near motor) to manually open or close the damper.
c. At 101ASPC Static Pressure Controller, remove the
NO
wire from the
micro switch. Connect A/C voltmeter (or test light) to
COM
and
NC
terminals of static pressure controller.
Zero V ac
(no light) should
be present, ensuring a connection is made between
COM
and
NC
. If
24V ac is present (light on), turn adjustment screw on 101ASPC Sta-
tic Pressure Controller clockwise (
CW
) until connection is made and
0V ac (no light) is obtained. Do Not Overtighten Adjusting Screw.
d. Verify bypass damper is
Closed
. Slowly back out adjusting screw
(
CCW
) until 24V ac (light on) is present ensuring no connection
between
COM
and
NC
. STOP. Slowly turn adjusting screw in (
CW
)
until 0V ac (no light) is present. STOP. Bypass damper should be on
verge of opening but still closed with all zone dampers open and the
blower fan on high speed.
e. If the bypass damper sizing and duct design are correct, this
completes the bypass damper setup. Connect all wires and proceed to
Bypass Checkout.
BYPASS CHECKOUT FOR STATIC
PRESSURE CONTROLLER
a. Make a cool call at the zone thermostat of the smallest (damper size) zone.
b. Verify all zone dampers are closed except for calling zone.
c. Verify noise at zone register is not excessive. Adjust static pressure
controller CCW to lower noise (airflow) or CW to increase airflow
until too noisy.
STOPS
AIRFLOW
BYPASS DAMPER
MOTOR
WINDOW
AIRFLOW
STATIC
PRESSURE
SENSOR
1
AIR
CONDITIONER
C
O
I
L
Insert the tube into the side of the duct, approximately
3”. Make sure the tube is perpendicular to the air flow.
1
A
B
C
E
F
G
H
D
Zonex Systems recommends de-energizing the bypass damper when the
blower fan turns off. If not installed as recommended, when the blower fan
turns off the bypass will fully close. Then when the blower fan turns back
on, there could be excessive air supplied to the calling zone, causing exces-
sive air noise until the bypass is able to open sufficiently. An alterna-
tive wiring diagram is provided using an additional static pressure sensor
to deenergize the bypass damper.
Alternative Wiring
