Trane LO - Manual (Page 64)

Tracer ® ZN.520
64 UNT-IOM-6
refer to the product-specific literature from that manufacturer.
If the unit is communicating with Tracer Summit and the supply fan
control programming point is configured for Tracer (the factory config-
ures as local), then Tracer Summit will control the fan regardless of
the fan mode switch position.
All Tracer ® ZN.520 lockouts (latching diagnostics) are manually reset
whenever the fan mode switch is set to the off position or when power
is restored to the unit. The last diagnostic to occur is retained until
the unit power is disconnected. Refer to Trane publication, CNT-IOP-2
Tracer ® ZN.520 Installation Operation and Programming Guide, for
specific instructions regarding the procedure for running the Tracer ®
ZN.520.
The heating and cooling setpoint high and low limits are always
applied to the occupied and occupied standby setpoints.
During the cooling mode, the Tracer ® ZN.520 controller attempts to
maintain the space temperature at the active cooling setpoint. Based
on the controller’s occupancy mode, the active cooling setpoint is
one of the following:
• Occupied cooling setpoint
• Occupied standby cooling setpoint
• Unoccupied cooling setpoint
The controller uses the measured space temperature, the active
cooling setpoint, and discharge air temperature along with the control
algorithm to determine the requested cooling capacity of the unit (0-
100%). The outputs are controlled based on the unit configuration and
the required cooling capacity. To maintain space temperature control,
the Tracer ® ZN.520 cooling outputs (modulating hydronic valve, 2-
position hydronic valve, or outdoor air economizer damper) are
controlled based on the cooling capacity output.
The cooling output is controlled based on the cooling capacity. At 0%
capacity, all cooling capacities are off and the damper is at minimum
position. Between 0 and 100% capacity, the cooling outputs are
controlled according to modulating valve logic (modulating valves) or
cycled on (2-position valves). As the load increases, modulating
outputs open further and binary outputs are energized longer. At
100% capacity, the cooling valve or damper is fully open (modulating
valves) or on continuously (and 2-position valves).
Unit diagnostics can affect fan operation, causing occupied and
occupied standby fan operation to be defined as abnormal. Refer to
the Troubleshooting section for more information about abnormal fan
operation.
Tracer Summit ® With
Supply Fan Control
Cooling Operation