Trane S*HF*20-75 Troubleshooting Manual page 136

DIAGNOSTICS Menu
Table 11: Diagnostics Troubleshooting Chart (continued)
Return Plenum Pressure
Sensor Failure
Used With: Return Fan
option.
Module: MPM
Rooftop Module Data
Storage Error
Used With: All units.
Module: RTM
SCM Communications
Failure
Module: SCM
136
Problem: The return
plenum pressure sensor
input is out of range and
one of the following is
occurring
a. The return plenum
pressure sensor value has
risen above +3.5 IWC
b. The return fan is on, the
return fan speed is 100%,
and the return plenum
pressure sensor value has
fallen below -0.75 IWC.
b. The return fan is off and
the return plenum pressure
sensor value has fallen
below -0.75 IWC.
Check: Return pressure
transducer assembly,
tubing and wiring. Return
fan drive and belt. Wiring
between the MPM and
sensor.
Problem: There is an older
version Human Interface
(prior to 32.xx) installed in
the unit or There was a data
transmission error.
Check:
a. Make sure the proper
Human Interface version is
installed in the unit.
b. This can also be caused
by an intermittent power
loss. Turn the unit off for 1-
2 minutes, then back on
again. If diagnostic
persists, then the RTM may
need to be replaced.
Problem: The RTM has lost
communications with the
SCM.
Check: Check unit wiring
between RTM and SCM
module.
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.
The diagnostic will be
displayed at the top level
status screen, and unit
operation will be
prevented.
A "Lockout" request is sent
to the compressor staging
control function. And a fail-
safe function in the SCM will
cause all SCM outputs to be
zeroed and de-energized.
(PAR) An automatic reset
occurs after the return
plenum pressure input
returns to within range for
10 continuous 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.
(PAR) An automatic reset
occurs after
communication has been
restored.
RT-SVP07B-EN