60 RT-SVX34C-EN
Startup
Zone Temperature - Occupied Cooling (CV only)
When the unit is in the cooling mode and the zone temperature raises above the cooling setpoint
controlband, the economizer and the compressor stages will be cycled as required by the zone
sensor, remote panel, or Tracer®.
Zone Temperature - Occupied Heating (CV only)
When the unit is in the heating mode and the zone temperature falls below the heating setpoint
controlband, the necessary stages of heat will cycle to raise the temperature to within the setpoint
controlband.
Supply Fan (CV only)
When the Fan Selection Switch is in the "AUTO" position and a call for cooling is initiated, the supply
fan will delay starting for approximately one second. When the Fan Selection Switch is in the "ON"
position, the supply fan will run continuously. If air flow through the unit is not proven by the
differential pressure switch (factory setpoint 0.15 " w.c.) within 40 seconds nominally, the RTRM will
shut off all mechanical operations, lock the system out, send a diagnostic to ICS, and the SERVICE
LED output will pulse. The system will remain locked out until a reset is initiated either manually
or through ICS or a mode transition from OFF to a non-OFF mode.
Supply Air Tempering (CV only)
This function allows the supply air temperature to be maintained within a low limit parameter
during minimum ventilation periods. When the system is in the "Heating" mode of operation, the
low limit parameter is equal to the heating setpoint minus 10 degrees F.
When an economizer is installed, air tempering is allowed with ICSTM when the fan system switch
is in the "ON" position with no call for heating. If the supply air temperature falls 10 degrees F below
the heating setpoint, the next available stage of heat will be turned on. It will remain on until the
supply air temperature reaches 10 degrees above the heating setpoint. A unit with modulating gas
heat will activate heat at 10 degrees below the setpoint and modulate to maintain the heating
setpoint.
VAV Supply Air Tempering (Only Available with Modulating Gas Heat)
Hot refrigerant gas will be modulated to prevent the Discharge Air Temperature from falling below
the Discharge Temperature Deadband. Upon satisfying the Supply Air Tempering requirements a
5 minute SA Tempering Delay timer will start whenever the modulating reheat valve is commanded
to 0 and must time out before the unit will be allowed to re-enter "Cool" mode. This timer will be
reset to 5 minutes whenever there is an active call for "Supply Air Tempering" demands. Tempering
will be discontinued whenever (a) the 5 minute "Supply Air Tempering Delay" timer has timed-out
and (b) there is an active cooling request for VAV Occupied Cooling.
Figure 39. Compressors
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