General Information
RT-SVX36K-EN 15
Phase Monitor (1U3) Standard on 20-89 ton
Continuously monitors line voltage to protect against
phase, loss, imbalance and reversal. If a fault is found with
the supply voltage a LED on the phase monitor will
indicate a fault and a unit External Auto Stop is activated
through the controls. 75 to 130 ton units have a phase
monitor on each compressor.
Multipurpose Module
MPM (Optional 1U105 used on units with
Return Fan or with Evaporative Condenser)
The Multipurpose Module (MPM) receives information
from the Return Plenum Pressure sensor and provides for
Return Fan control to maintain this pressure to the Active
Return Plenum Pressure Setpoint and Deadband.The
liquid line pressure sensor inputs for the refrigeration
circuits are received through the MPM in support of head
pressure control on Evaporative condenser units.
Input Devices & System Functions
The descriptions of the following basic Input Devices used
within the UCM network are to acquaint the operator with
their function as they interface with the various modules.
Refer to the unit's electrical schematic for the specific
module connections.
Constant Volume (CV), Single
Zone Variable Air Volume (SZVAV)
& Variable Air Volume (VAV)
Sensors and Controls
Supply Air Temperature Sensor (3RT9)
This analog input device monitors the supply air
temperature for; supply air temperature control (used with
discharge temperature control), supply air temperature
reset (used with discharge temperature control), supply air
temperature low limiting (used with discharge
temperature control), and supply air tempering. It is
mounted in the supply air discharge section of the unit and
is connected to the RTM (1U48).
Return Air Temperature Sensor (3RT6)
This analog input device is used with a return humidity
sensor when the comparative enthalpy option is ordered.
It monitor s the return air temperature and compares it to
the outdoor temperature to establish which temperature is
best suited to maintain the cooling requirements. It is
mounted in the return air section and is connected to the
ECEM (1U52).
Entering Evaporator Temperature Sensor
(3RT28 and 3RT29)
This analog input device is used with the Leaving
EvaporatorTemp sensor to provide Low Charge Protection
of the refrigerant systems.The difference in these two
temperatures will be monitored during compressor
operation and compressor circuits will be shut down if this
difference exceeds a Human Interface selectable setpoint
value.
Leaving EvaporatorTemperature Sensor
(3RT14 and 3RT15)
An analog input device used to monitor the refrigerant
temperature inside the evaporator coil to prevent coil
freezing. It is attached to the suction line near the
evaporator coil and is connected to the MCM. It is factory
set for 30°F and has an adjustable range of 25°F to 35°F.The
compressors are staged “Off” as necessary to prevent
icing. After the last compressor stage has been turned
“Off”, the compressors will be allowed to restart once the
evaporator temperature rises 10°F above the “coil frost
cutout temperature” and the minimum three minute “Off”
time has elapsed.
Filter Switch (3S21 and 3S58)
This binary input device measures the pressure
differential across the unit filters. It is mounted in the filter
section and is connected to the RTM (1U48). A diagnostic
SERVICE signal is sent to the remote panel if the pressure
differential across the filters is at least 0.5" w.c.The
contacts will automatically open when the pressure
differential across the filters decrease to 0.4" w.c.The
switch differential can be field adjusted between 0.17" w.c.
to 5.0" w.c. ± 0.05" w.c.
Supply and Exhaust Airflow Proving Switches
(3S68 and 3S69)
3S68 is a binary input device used to signal the RTM when
the supply fan is operating. It is located in the supply fan
section of the unit and is connected to the RTM (1U48).
During a request for fan operation, if the differential switch
is detected to be open for 40 consecutive seconds;
compressor operation is turned “Off”, heat operation is
turned “Off”, the request for supply fan operation is turned
“Off” and locked out, exhaust dampers (if equipped) are
“closed”, economizer dampers (if equipped) are “closed”,
and a manual reset diagnostic is initiated.
3S69 is a binary input device used on all rooftop units
equipped with an exhaust fan. It is located in the exhaust/
return fan section of the unit and is connected to the RTM
(1U48). During a request for fan operation, if the
differential switch is detected to be open for 40
consecutive seconds, the economizer is closed to the
minimum position setpoint, the request for exhaust fan
operation is turned “Off” and locked out, and a manual
reset diagnostic is initiated.The fan failure lockout can be
reset; at the Human Interface located in the unit's control
panel, byTracer, or by cycling the control power to the
RTM (1S70 Off/On).
Lead-Lag
Is a standard mode of operation on 20 thru 130Ton units.
It alternates the starting between the first compressor of
To Next Page
Loading...
Need help?
General
