50
IM 738-2
Mechanical Installation:
Installing Duct Static Pressure Sensor Taps
Installing Duct Static Pressure Sensor Taps
For all VAV units, duct static pressure taps must be field
installed and connected to the pressure sensors in the unit.
Sensor SPS1 is standard; additional sensor SPS2 is optional.
These sensors are located in the main control panel (see
“Control Panel” on page 10).
Carefully locate and install the duct static pressure sensing tap.
Improperly locating or installing the sensing tap causes
unsatisfactory operation of the entire variable air volume
system. Below are pressure tap location and installation
recommendations.The installation must comply with local
code requirements
1
Install a tee fitting with a leak-tight removable cap in each
tube near the sensor fitting. This facilitates connecting a
manometer or pressure gauge if testing is required.
2
Use different colored tubing for the duct pressure (HI) and
reference pressure (LO) taps, or tag the tubes.
Daikin
recommends ¼" plastic tubing.
3
Locate the duct pressure (HI) tap near the end of a long
duct to ensure that all terminal box take-offs along the run
have adequate static pressure.
4
Locate the duct tap in a nonturbulent flow area of the duct.
Keep it several duct diameters away from take-off points,
bends, neckdowns, attenuators, vanes, or other
irregularities.
5
Use a static pressure tip (Dwyer A302 or equivalent) or the
bare end of the plastic tubing for the duct tap. (If the duct is
lined inside, use a static pressure tip device.)
6
Install the duct tap so that it senses only static pressure (not
velocity pressure). If a bare tube end is used, it must be
smooth, square (not cut at an angle) and perpendicular to
the airstream (see Figure 62).
7
Locate the reference pressure (LO) tap somewhere near the
duct pressure tap within the building (see Figure 61). If the
reference tap is not connected to the sensor, unsatisfactory
operation will result.
8
Route the 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 61). Connect the tubes to
appropriate barbed fittings in the control panel. (Fittings are
sized to accept ¼" plastic tubing.)
Figure 61. Static pressure tubing entrance location
Figure 62. Pressure sensing tubing installation
Static pressure
tubing
M a i n o n t r o l P a n e l
o n d e n s e r S e c t i o n
" H I l i n e "
" L O " l i n e
R e m o t e S e n s e P o i n t
S P S
R o o f
T u b i n g E x t e n d s
t h r u A p p r o x . / 8 "
R u b b e r
G r o m m e t
D u c t w o r k
( R e m o t e L o c a t i o n )
T o S e n s o r
" H I " i n p u t
T o S e n s o r
" L O " I n p u t
P r e s s u r e S e n s i n g
T u b i n g
Summary of Contents for RDT-135c
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