Trane S*HF*20-75 Troubleshooting Manual page 135

Table 11: Diagnostics Troubleshooting Chart (continued)
Return Air Temperature
Sensor Failure
Used With: Comparative
Enthalpy installed, or
Energy Recovery Wheel
option.
Module: ECEM
Return Fan failure
Module: RTM
RT-SVP07B-EN
Problem: The ECEM RA
Temperature Sensor has
been assigned to at least
one function, and this
sensor signal is out of range
(Temp < -55 F or Temp >
209 F).
Check: The HI value and
wiring between the ECEM
module and the sensor.
Removing the plug from the
ECEM module there should
be no shorts, opens and
sensor resistance should be
between 830 ohms and
345.7Kohms.
Problem: The return fan
proving input is detected
OPEN for 40 continuous
seconds during any period
of time in which the return
fan relay is ON.
Check: The return fan
drive and belt. Faulty wiring
with the return fan proving
switch circuit.
Note: A communications
error from the MPM will also
cause a return fan failure
lockout.
The Economizer Enable r.e.
Enthalpy function reverts
to Reference Enthalpy
changeover ("Level 2")
control.
The unit will trip all outputs,
de-energize dx cooling,
staged heating, fans, etc.,
and will drive all analog
ouputs closed/stop, fan
speed, dampers,
modulating heat, etc.
DIAGNOSTICS Menu
(PAR) An automatic reset
occurs after the RA
Temperature input returns
to its allowable range
continuously for 10
seconds.
(PMR) A manual reset is
required anytime after the
diagnostic is set. The
diagnostic can be reset by
the Human Interface or
Tracer, or by cycling power
to the RTM.
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