32
Step 12 — Route VAV Static Pressure Sensors
VAV DUCT PRESSURE TRANSDUCER
The VAV duct pressure transducer (VAV inverter pressure trans
-
ducer) is located behind the filter access door on the lower inner
panel. See Fig. 44. A section of field-supplied
1
/
4
-in. plastic tubing
must be run from the high pressure tap on the differential pressure
switch and connected to a field-supplied tap in the supply-air duct.
The tap is usually located
2
/
3
of the way out on the main supply
duct. Remove plug button in panel to route tubing.
VAV BUILDING PRESSURE TRANSDUCER
The VAV building pressure transducer (modulating power exhaust
pressure transducer) is located behind the filter access door on the
lower inner panel. See Fig. 44. A section of field-supplied
1
/
4
-in.
plastic tubing must be run from the high pressure tap on the differ
-
ential pressure switch to the conditioned space. The pressure tube
must be terminated in the conditioned space where a constant
pressure is required. This location is usually in an entrance lobby
so that the building exterior doors will open and close properly.
Remove plug button in panel to route tubing.
The low pressure tap is factory-routed to the atmosphere. For a
positive-pressure building, route the high tap to building air and
low tap to atmosphere. For a negative-pressure building, route the
high tap to atmosphere and the low tap to building air.
Fig. 44 —
Pressure Transducer Locations
Step 13 — Install All Accessories
After all the factory-installed options have been adjusted, install
all field-installed accessories. Refer to the accessory installation
instructions included with each accessory.
The 48A Series units have a large number of factory-installed
options which were previously available only as accessories.
Some of the available options can also be installed in the field if
needed. In most cases the units have been pre-wired so that the
accessories can be easily installed. Instructions are shipped with
each accessory. Configuration of the controls for these accessories
as well as the factory-installed options can be found in the
Controls, Start-up, Operation, Service and Troubleshooting book.
The following is a list of some of the common accessories:
• Thermostats and space temperature sensors
• LP (liquid propane) conversion kit
• Accessory barometric relief damper
• Accessory power exhaust
• Non-modulating to modulating power exhaust
• Condenser coil hail guards
• Outdoor humidity sensor (used for economizer enthalpy
changeover)
• Return air humidity sensors (used for economizer differential
enthalpy changeover, factory-installed with Humidi-MiZer
option)
• Return air smoke detector
• Controls expansion module (used for interface to building
management systems, not typically needed on system with
the Carrier Comfort Network
®
[CCN] system)
• Plugged filter sensor
FIELD-FABRICATED WIND BAFFLES
In areas with prevailing winds of more than 5 mph and where tem
-
peratures drop below 32°F, wind baffles must be field fabricated to
ensure proper cooling cycle operation at low-ambient tempera
-
tures with Motormaster V controls. Baffles are not needed on size
060 units with MCHX (microchannel heat exchangers). See
Fig. 45 for baffle details. Use 20-gage galvanized sheet metal, or
similar corrosion-resistant material for the baffles. Use field-sup
-
plied screws to attach baffles to unit. Screws should be
1
/
4
-in. di
-
ameter or larger. Screws should not be more than
1
/
2
inch in
length. Drill required screw holes for mounting baffles.
a48-6976
AUXILIARY
CONTROL BOX
PRESSURE TRANSDUCERS
(INSIDE OF PANEL)
IMPORTANT: Carrier recommends the installation of
field-fabricated wind baffles on all vertically oriented con
-
denser coils when operating in environments with prevail
-
ing winds of more than 5 mph and where temperatures drop
below 32°F. See the Motormaster accessory installation
guide for instructions.
WARNING
To avoid the possibility of electrical shock, open all discon
-
nects before installing or servicing this accessory.
CAUTION
To avoid damage to refrigerant coils, electrical components,
and wiring use extreme care when drilling screw holes and
screwing in fasteners.
