Unit Startup
RT-SVX24J-EN
101
protection circuit before closing “Stage 1". After the first
functional stage has started, the compressor module
monitors the saturated refrigerant temperature and closes
the condenser fan output contact, when the saturated
refrigerant temperature rises above the “lower limit”
setpoint.
Units with an Economizer
Upon entering an “occupied” mode of operation, the RTM
receives input from the remote panel to start the supply
fan. For constant volume applications, the RTM supply fan
contacts close which energizes the supply fan contactor.
When the supply fan starts, the fan proving switch closes,
signaling the RTM that airflow has been established. The
RTM opens the economizer dampers to the specified
“minimum position”.
When a cooling request is sent to the RTM from the zone
temperature sensor, the RTM evaluates the operating
condition of the system using the supply air temperature
input and the outdoor temperature input before sending
the request to the MCM for mechanical cooling. If the
outdoor conditions are suitable for cooling (temperature
and humidity are within specified setpoints), the RTM will
attempt to maintain the zone temperature without using
any compressors. If the zone temperature can not be
maintained within the setpoint deadband, the RTM sends
a cooling request to the MCM. The compressor module
checks the compressor protection circuit before closing
“Stage 1". After the first functional stage has started, the
compressor module monitors the saturated refrigerant
temperature and closes the condenser fan output contact,
when the saturated refrigerant temperature rises above
the “lower limit” setpoint.
Units with TRAQ™ Sensor
The outside air enters the unit through the TRAQ Sensor
assemblies and is measured by velocity pressure flow
rings.The velocity pressure flow rings are connected to a
pressure transducer/solenoid assemblies.The solenoid is
used for calibration purposes to compensate for
temperature swings that could affect the transducer. The
Ventilation Control Module (VCM) utilizes the velocity
pressure inputs, the RTM outdoor air temperature input,
and the minimum outside air CFM setpoint to modify the
volume (CFM) of outside air entering the unit as the
measured airflow deviates from setpoint.
When the optional temperature sensor is installed and the
Preheat function is enabled, the sensor will monitor the
combined (averaged) outside air and return air
temperatures. As this mixed air temperature falls below
the Preheat Actuate Temperature Setpoint, the VCM will
activate the preheat binary output used to control a field
installed heater. The output will be deactivated when the
temperature rises 5 above the Preheat Actuate
Temperature Setpoint.
When the optional CO
2
sensor is installed and DCV is
enabled, the OA damper will be modulated to control CO
2
concentrations. If the CO
2
concentration is greater than
the Design Minimum CO
2
Setpoint the OA damper will be
opened to the Design Minimum OA Damper Setpoint (w/
oTRAQ) or until the Design Minimum OA Flow Setpoint is
met (w/ TRAQ).
If the CO
2
concentration is less than the DCV Minimum
CO
2
Setpoint the OA damper will be closed to the DCV
Minimum OA Damper Setpoint (w/o TRAQ) or until the
DCV Minimum OA Flow Setpoint is met (w/ TRAQ).
If the CO
2
concentration is between the Design Minimum
CO
2
Setpoint and the DCV Minimum CO
2
Setpoint the OA
damper will be modulated proportionally between the
Design Minimum OA Damper Setpoint and the DCV
Minimum OA Damper Setpoint (w/ TRAQ) and between
the Design Minimum OA Flow Setpoint and the DCV
Minimum OA Flow Setpoint (w/o TRAQ).
Frostat™ Control
The compressor module utilizes an evaporator
temperature sensor, mounted on the suction line of each
circuit, to protect the evaporator from freezing. If the
evaporator temperature approaches the specified
setpoint, adjustable between 25°F and 35°F, the
compressor(s) will be cycled “off”.The compressors will
not be allowed to restart until the evaporator temperature
has risen 10 F above the specified cutout temperature and
the compressor(s) have been off for a minimum of three
minutes.
Lead/Lag Operation
When Lead/Lag is enabled, each time the system cycles
after having stages 1 and 2 “On”, “Stage 2" and the
corresponding condenser fan output will start first. The
compressor module cycles the compressors “On” and
“Off” to keep the zone temperature within the cooling
setpoint deadband. The condenser fans are cycled “On”
and “Off” to maintain the saturated refrigerant
temperature within the specified controlband.
Units equipped with 100% modulating
exhaust
The exhaust dampers are controlled through an Exhaust/
Comparative Enthalpy Module (ECEM).The ECEM module
receives input from a space transducer and modulates the
exhaust dampers to maintain the space pressure to within
the specified setpoint controlband.
Modulating Dehumidification (Hot Gas
Reheat) Sequence of Operation
When the relative humidity in the controlled space (as
measured by the sensor assigned to space humidity
sensing) rises above the space humidity setpoint,
compressors and the supply fan will energize to reduce the
humidity in the space.
All compressors on both refrigerant circuits will be staged
up during active dehumidification. Circuit #1 is designated
the reheat circuit and will feature additional refrigerant
Содержание SEHJ090-162
Страница 40: ...Dimensional Data 40 RT SVX24J EN Figure 13 Evaporative condenser water connection locations RIGHT SIDE VIEW ...
Страница 48: ...Installation 48 RT SVX24J EN Figure 18 Ductwork conversion ...
Страница 58: ...Installation 58 RT SVX24J EN Figure 36 5 Connected tubes 6 install panels Connected tubes 5 6 ...
Страница 75: ...Installation RT SVX24J EN 75 Figure 51 Hot water coil piping Figure 52 Steam coil piping ...
Страница 87: ...Installation RT SVX24J EN 87 Figure 57 Typical field wiring diagram for 90 to 162 ton CV control options ...
Страница 89: ...Installation RT SVX24J EN 89 Figure 59 Typical field wiring diagram for 90 to 162 ton VAV control options ...