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back wall of the discharge plenum. Sensing tubes should
enter the unit discharge plenum through the main supply
duct trunk. Make sure that duct penetrations are sealed
and that tubing is protected by rubber grommets. Care-
fully connect the HI and LO tubes to the appropriate
sensor fittings.
Figure 10. Duct static pressure tap installation
Figure 11. Static pressure tubing entrance locations
Installing Building Static Pressure Sensor Taps
If a unit has direct building static pressure control capability,
static pressure taps must be field installed and connected to
pressure sensor SPS2 in the unit. This sensor is located at
the back of the discharge section (see “Control Panel Loca-
tions” in the “Unit Description” section of this manual).
The two static pressure sensing taps must be carefully
located and installed. Improper location or installation of the
sensing taps will cause unsatisfactory operation. Following
are pressure tap location and installation recommendations
for both building envelope and lab, or “space within a space,”
pressure control applications. The installation must comply
with local code requirements.
Fragile sensor fittings. May damage pressure sensor.
If tubing must be removed from a pressure sensor fitting,
use care. Do not wrench the tubing back and forth to
remove or the fitting may break off.
Building pressurization applications
1. Install a tee fitting with a leak-tight removable cap in each
tube near the sensor. This will facilitate connecting a
manometer or pressure gauge if testing is required.
2. Locate the duct pressure (HI) tap in the area that requires
the closest control. Typically, this is a ground level floor
that has doors to the outside.
3. Locate the building tap so that it is not influenced by any
source of moving air (velocity pressure). These sources
may include air diffusers or outside doors.
4. Route the building tap tube to sensor SPS2 mounted on
the back wall of the discharge plenum. Sensing tube
should enter the unit discharge plenum through the main
supply duct trunk. Make sure that duct penetration is
sealed and that tubing is protected by a rubber grommet.
Carefully connect to the HI sensor fitting.
5. Locate the reference pressure (LO) tap on the roof. Keep
it away from the condenser fans, walls, or anything else
that may cause turbulence. Mount it high enough above
the roof so that it is not affected by snow. If the reference
tap is not connected to the sensor, unsatisfactory opera-
tion will result.
6. Use an outdoor static pressure tip (Dwyer A306 or equiva-
lent) to minimize the adverse effects of wind. Place some
type of screen over the sensor to keep out insects.
Loosely packed cotton works well.
7. Route the outdoor tap tube to sensor SPS2 mounted on
the back wall of the discharge plenum. Sensing tube
should enter the unit discharge plenum through a hole cut
in the back wall of the discharge plenum. Make sure that
the penetration is sealed and that tubing is protected by a
rubber grommet. Carefully connect to the LO sensor fitting.
Lab pressurization applications
1. Install a tee fitting with a leak-tight removable cap in each
tube near the sensor. This will facilitate connecting a
manometer or pressure gauge if testing is required.
2. Use different colored tubing for the controlled space
pressure (HI) and reference pressure (LO) taps, or tag the
tubes.
3. Regardless of whether the controlled space is positive or
negative with respect to its reference, locate the HI
pressure tap in the controlled space. (The set point can be
set between –0.2" and 0.2" w.c.)
4. Locate the reference pressure (LO) tap in the area sur-
rounding the controlled space. If the reference tap is not
connected to the sensor, unsatisfactory operation will
result.
5. Locate both taps so that they are not influenced by any
source of moving air (velocity pressure). These sources
may include air diffusers or doors between the high and
low pressure area.
6. Route the tap tubes between the curb and the supply
duct, and feed them into the unit through the knockout in
the bottom of the control panel (see Figure 11).
7. Connect the tubes to the appropriate
1
⁄
4
" fittings on sensor
SPS2. Assure that the sensor does not support the weight
of the tubing; use tube clamps or some other means.
To Sensor
“HI” Input
Pressure Sensing
Tubing
To Sensor
“LO” Input
Tube Clamps
Tubing Extends
Thru Approx.
1/8"
Rubber
Grommet
Outdoor Static
Pressure Tubing
Entrance (Field
Cut)
Main Control
Panel
Indoor Static
Pressure Tubing
Entrance
Control Wiring
Raceway Cover
!
CAUTION
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