Unit installation

Controls
72 SCXF-SVX01K-EN
operate if the temperature of the outside air falls below the
lockout setpoint. When the temperature rises 5°F above
the lockout setpoint, the compressors will operate.The
setpoint for units without the low ambient option is 50°F.
For units with the low ambient option, the setpoint is 0°F.
The setpoints are adjustable at the human interface panel.
Return Air Temperature Sensor
The return air temperature sensor is an analog input
device used with a return humidity sensor on units with
the comparative enthalpy option.The sensor monitors the
return air temperature and compares it to the outdoor
temperature to establish which temperature is best suited
to maintain cooling requirements. It is mounted in the
return air path and connected to the ECEM.
Supply Fan Circuit Breaker, Fuses, and
Overloads
The supply fan motor is protected by either circuit
breakers fuses or a combination of fuses and overloads,
dependent upon unit configuration. Circuit breakers are
used on units without a VFD. They will trip and interrupt
the motor power supply if the current exceeds the breaker
trip value.The RTM shuts all system functions off when
detecting an open fan proving switch. Units with a VFD
have fuses to protect the VFD and motor. Units with aVFD
w/bypass have fuses to protect VFD circuit and overloads
to protect the motor when in bypass.
Supply Air Temperature Low Limit
The supply air temperature low limit function uses the
supply air temperature sensor input to modulate the
economizer damper to the minimum position if the supply
air temperature falls below the occupied heating setpoint
temperature.
Supply Air Temperature Sensor
The supply air temperature sensor is an analog input
device. It monitors the supply air temperature for supply
air temperature control, supply air temperature reset,
supply air temperature low limiting, and supply air
tempering. It is mounted in the supply air discharge
section of the unit and connected to the RTM.
Supply Airflow Proving Switches
This is binary input device used on units to signal the RTM
when the supply fan is operating. It is mounted in the
supply fan section and is connected to the RTM. During a
request for fan operation and if the differential switch
opens for 40 consecutive seconds, compressor operation
turns off, heat operation turns off, the request for supply
fan operation turns off and locks out, economizer damper
option closes, and a manual reset diagnostic initiates.
Low Entering Air Protection Device (LEATPD)
The low entering air protection device (LEATPD) is a binary
input on units with hydronic heat or a waterside
economizer. It is optional on water-cooled units.
If the LEATPD is on a unit with factory-installed heat, it is
mounted in the heat section and connected to the heat
module. If the entering air temperature to the heating coil
falls to 40°F, the normally open contacts on the LEATPD
close and cause the following events:
a. the hydronic heat actuator fully opens.
b. the supply fan turns off
c. the outside air damper closes
d. the SERVICE light at the remote zone sensor option
turns on.
e. a LEATPD diagnostic displays at the human
interface panel.
If the LEATPD is on a water-cooled unit without factory-
installed heat, it is wired to the WSM. It will trip if the
entering water temperature falls to 34°F, open the
economizer valve, and energize the pump output.
High Duct Temp Thermostat Option On Units
with a TCI
The high duct temperature thermostats are binary input
devices used on units with aTrane communication
interface module (TCI).They provide a high limit unit
shutdown and require a manual reset.The thermostats are
factory set to open if the supply air temperature reaches
240°F, or the return air temperature reaches 135°F. Once
tripped, the thermostat requires a manual reset. Reset by
pressing the sensor’s reset button when the air
temperature decreases approximately 25°F below the
cutout point.
Filter Switch
The filter switch is a binary input device that measures the
pressure differential across the unit filters. It is mounted in
the filter section and connected to the RTM. A diagnostic
SERVICE signal displays at the remote panel if the
pressure differential across the filters is at least 0.5” w.c.
The contacts automatically open when the pressure
differential across the filters decrease to 0.4” w.c.The
switch differential is field adjustable between 0.17” to 5.0”
w.c. ± 0.05 “.
High Duct Static Switch Option
The high duct static switch is field-mounted in the
ductwork or plenums with smoke dampers. It will cause a
manual reset diagnostic if the duct static exceeds the pre-
set static limit.The static limit is adjustable at the HI.