Trane Tracer ZN.520

Binary inputs
CNT-SVX04A-EN
27
Condensate overflow
The condensate overflow switch in the
condensate pan automatically resets when
the condensation returns to normal levels.
However, you must manually reset the
controller to clear the condensate overflow
diagnostic and restart the unit.
A condensate overflow float switch detects a condensate overflow condition.
The condensate overflow switch is physically connected to a binary input of the
controller (BI 2). When the condensation reaches the trip point, the binary input
detects the diagnostic condition. By default, a condensate overflow signal will
generate a diagnostic that disables fan operation, closing all unit water valves
(when present), disabling the DX compressor (when present), turning off any
electric heat (when present), and closing the economizer outdoor air damper
(when present). The condensate overflow diagnostic does not affect the
generic binary output (when present). Although the actual condensate overflow
switch automatically resets when the condensation returns to a normal level,
manually reset the condensate overflow diagnostic to clear the diagnostic from
the controller and restart the unit.
Low coil temperature detection
The low temperature detection device
automatically resets when the coil
temperature returns to normal. However,
you must manually reset the low coil
temperature detection diagnostic to clear
the diagnostic and restart the unit.
Low coil temperature detection protects the coil for hydronic/steam units. A
binary input and a low temperature detection device (or freezestat) detects the
low temperature signal. The ComfortLink zone controller can protect the coil
with one binary input. When the controller detects the low temperature
detection signal, the controller generates a diagnostic that disables the fan,
opens all unit water valves, and closes the economizer outdoor air damper
(when present). The low coil temperature detection diagnostic does not affect
the generic binary output (when present). Even though the actual low coil
temperature detection device automatically resets when the coil/heat
exchanger temperature returns to a normal value, you must manually reset the
low coil temperature detection diagnostic to clear the diagnostic from the
controller and restart the unit.
The controller includes an automatic
diagnostic reset function in which the
controller attempts to automatically
recover from the low coil temperature
detection diagnostic. For more information
on the automatic diagnostic reset function,
refer to “Resetting diagnostics” on
page 94.
Fan status
The fan status switch protects the unit in belt drive or unit ventilator
applications. A Low AirFlow—Fan Failure diagnostic is detected when the
control is commanding the fan On and the fan status switch has been open for
one minute, or if the fan status switch does not close the binary input within
one minute of the controller commanding the fan On. This is a latching
diagnostic and discontinues unit operation until the diagnostic has been
cleared from the controller. The Low AirFlow—Fan Failure diagnostic does not
affect the generic binary output (when present). Additional details can be found
in “Diagnostics” on page 92.