u
nIT
o
PTIons
Duct Static Pressure Sensor
All units provided with variable air volume control include a
factory-mounted static pressure sensor (SPS1) . The unit also
can have an optional second static pressure sensor, SPS2 .
The sensor is factory wired and requires field installation of
1/8" I .D . sensor tubing to the selected duct location .
NOTE: Be sure that tubing complies with local code
requirements . Flame retardant plastic or metal tubing
may be required . Carefully select the ductwork
sensing point for the pressure sensor . Improper
location of the sensing point results in unsatisfactory
operation of the entire variable air volume system .
Adhere to the following guidelines:
1 . Position sensors near the end of long duct runs so all
terminal box take-offs along the run have adequate static
pressure to operate .
2 . Position the end of the sensing tube perpendicular to the
airflow to sense only static pressure.
3 .
Locate the sensing tube in a non-turbulent flow area of
the duct . Keep several duct widths away from take-off
points, bends, or neck downs .
Mounting Instructions
1 . Drill a hole in the duct at the remote sensing point and
install a rubber grommet (
Figure 24
) .
2 . Insert the sensing tube 1/8" into the duct and securely
clamp tubing to the duct, being sure not to stress or kink
the tubing .
NOTE: The end of the sensing tube must be smooth and cut
straight across . An angle cut affects operation .
3 . Clamp a second tube to the outside of the duct at the
location of the sensing point .
4 . Run both tubes along the ductwork and back to the unit .
5 . Route the tubing to the pressure sensor (SPS1) by
drilling two holes through the unit upright post .
6 . Use a grommet at each hole to protect the tubing and
seal the cabinet .
NOTE: To avoid confusion between “high” and “low” tubing,
use two different tubing colors and record this
information along with the sensing point location on
the master building blueprints .
7 . Connect tubing to the high and low ports at the patch
panel in the main control section .
Figure 24: Sensor Mounting
Freezestat
(ETL Marked Units Only)
A non-averaging type freezestat (FS1/FS2) is provided to
protect hydronic coils from subfreezing temperatures . If the
unit has an economizer coil, the control is mounted on the
entering face of the economizer coil . If the unit does not have
an economizer coil, the control is mounted on the leaving
face of the hot water coil . Upon sensing a temperature above
specification, the unit shuts down, opens the hydronic control
valves, and sends an alarm indication via the MicroTech III
controller. The freezestat has a field-adjustable set point range
of 35°F to 45°F . To change the set point, turn the adjustment
screw until the pointer lines up with the desired cutout point .
The adjustment screw is accessible at the bottom of the control
or at the top when the cover is removed .
Condenser Water Flow
Switch
The Water Flow sensor (WF1) is available to verify flow to the
unit condenser before compressor operation is allowed . The
flow sensor is factory installed in the unit on the entering water
condenser pipe . If the unit senses a loss of condenser water,
cooling is locked out via the MicroTech III controller . When
flow is restored, the unit automatically resets. The Water Flow
sensor operates on the calorimetric principle using the cooling
effect of the flowing condenser water around its stainless steel
tip to provide flow detection.
To sensor
"HI" input
To sensor
"LO" input
Tube clamps
Pressure
sensing
tubing
Rubber
grommet
Tubing extends
thru approx. 1/8"
IM 1032-2 • Self-Contained Air Conditioning System 32 www .DaikinApplied .com
u
nIT
o
PTIons