RT-SVX36G-EN
21
General Information
a. diagnostic and mode status signals to the remote panel (LEDs) and to the Human Interface.
b. control of the binary Alarm output on the RTM.
c. control of the binary outputs on the GBAS module to inform the customer of the operational
status and/or diagnostic conditions.
Low Ambient Compressor Lockout
Utilizes an analog input device. When the system is configured for low ambient compressor
lockout, the compressors are not allowed to 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
are allowed to 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
inside the unit control panel.
Space Pressure Transducer (3U62)
This is an analog input device that modulates the exhaust dampers to keep the space pressure
within the building to a customer designated control band. It is mounted in the filter section just
above the exhaust damper actuator and is connected to the ECEM (1U52). Field supplied pneumatic
tubing must be connected between the space being controlled and the transducer assembly.
Morning Warm-Up - Zone Heat (not SZVAV)
When a system changes from an unoccupied to an occupied mode, or switches from STOPPED to
AUTO, or power is applied to a unit with the MWU option, the heater in the unit or external heat
will be brought on if the space temperature is below the MWU setpoint. The heat will remain on
until the temperature reaches the MWU setpoint. If the unit is VAV, then the VAV box/unocc relay
will continue to stay in the unoccupied position and the VFD output will stay at 100% during the
MWU mode. When the MWU setpoint is reached and the heat mode is terminated, then the VAV
box/unocc relay will switch to the occupied mode and the VFD output will be controlled by the duct
static pressure. During Full Capacity MWU the economizer damper is held closed for as long as it
takes to reach setpoint. During Cycling Capacity MWU the economizer damper is allowed to go to
minimum position after one hour of operation if setpoint has not been reached.
Compressor Motor Winding Thermostats
CSHD compressors (20-70 Ton) Air-Cooled and (24-80 Ton) Evaporative Condensers
The compressors contains an internal line break overload which stops the compressors under a
number of operating conditions that cause excessive motor temperature. These include rapid
cycling, loss of charge, abnormally high suction temperatures, excessive amperage, phase loss
and low voltage
CSHN Compressors (75 - 130 Ton) Air-Cooled and (89 Ton) Evaporative Condensers
PTC sensors are embedded in the motor windings of each Scroll compressor. These sensors are
wired to the protection module which protects the motor from over temperature that can occur
under a number of abnormal operating conditions. These include rapid cycling, loss of charge,
abnormally high suction temperatures, low voltage and excessive amperage.
During a request for compressor operation, if the Compressor Module (SCM) detects a problem
outside of it's normal parameters, it turns any operating compressor(s) in that circuit “Off”, locks
out all compressor operation for that circuit, and initiates a manual reset diagnostic.
Discharge Line Thermostat
The first compressor on each circuit is equipped with a Discharge Line Thermostat. If the
temperature of the line exceeds 210°F the thermostat interrupts the 115V circuit for the
compressors and both of the compressors on that circuit will be de-energized. Once the
temperature drops below 170°F the thermostat will close and allow the compressor to be
energized.
