Trane Tracer AH540 Setup And Operation page 31

Analog inputs
where 20 mA is equal to 100% relative humidity (see Table 76 on
page 107).
A space relative humidity input is required for space dehumidification
control. If valid space relative humidity input does not exist, space dehu-
midification control will be disabled. The controller will accept a valid
hard-wired sensor input or a communicated value for space relative
humidity. If both a hard-wired and a communicated value exist, the con-
troller will use the communicated value for control. The communicated
value has priority over the hard-wired input.
When a space relative humidity input is established (either hard-wired or
communicated), the controller generates a Humidity Input Failure diag-
nostic if the signal is no longer valid, and disables space dehumidifica-
tion. If the sensor or communicated value returns to a valid input, the
controller automatically clears the diagnostic and allows space dehumidi-
fication operation.
CO sensor
2
When using the universal analog input with a CO sensor first configure
2
the controller input using the Rover service tool for CO and then make
2
the wiring connections. The sensor must provide a 4–20 mA signal, where
20 mA is equal to 2000 ppm (see Table 77 on page 108).
The CO input, reported in parts per million, is not used for any AH540/
2
541 control purposes. Instead the input is reported to the building auto-
mation system using Comm5 or other devices as a data point. When a
CO sensor input is established, the controller generates a CO Sensor
2 2
Failure diagnostic if the signal is no longer valid, but the diagnostic has
no effect on controller operation. If the sensor returns to a valid input, the
controller automatically clears the diagnostic.
Entering water temperature
The universal analog input configured as entering water temperature
accepts a 10 kΩ thermistor input (Table 74 on page 106). A valid entering
water temperature value (hard-wired or communicated) is required for
two-pipe changeover operation for space temperature control air-handling
units with one hydronic coil. If both a hard-wired and a communicated
value exist, the controller will use the communicated value for two-pipe
changeover operation. The communicated value has priority over the
hard-wired input.
When valid entering water temperature input is available to the control-
ler it is used to determine if hot or cold water capacity is available for
space heating and cooling operation. If the entering water temperature
input is not valid, the controller assumes hot water exists and disables
hydronic cooling operation.
When an entering water temperature input is established (either hard-
wired or communicated), the controller generates an Entering Water
Temp Failure diagnostic, if the signal is no longer valid, and assumes a
cold entering water temperature. If the sensor or communicated value
CNT-SVX05B-EN 21