Trane S*HF*20-75 Troubleshooting Manual page 128

DIAGNOSTICS Menu
Table 11: Diagnostics Troubleshooting Chart (continued)
High Superheat
(Ckt-1 or Ckt-2)
Used With: DX cooling.
Module: MCM
Leaving Recovery
Exhaust Temp Failure
Used With: Energy
Recovery Wheel option.
Module: MPM
Low Air Temperature
Limit Trip (formerly:
Freezestat Trip)
Used With: Hydronic or
steam heat option, or w/
chilled water installed.
Module: HEAT
128
Problem: DX cooling
operation has been active
for 10 minutes on the given
circuit, and the difference
in the entering and leaving
evaporator temperatures
is:
a. less than the Evaporator
Temperature Differential
Setpoint for a period of ten
minutes, and...
b. greater than the
Evaporator Temperature
Differential Setpoint minus
5 F.
Check: Refrigerant.
Sensor integrity.
Problem: The Leaving
Recovery Exhaust Temp
sensor is out of range.
(Temp < -55 F or Temp >
209 F)
Check: The HI value and
wiring between the MPM
module and the sensor.
Removing the plug from the
MPM module there should
be no shorts, opens and
sensor resistance should be
between 830 ohms and
345.7Kohms.
Problem: The Low Air
Temperature Limit Trip
condition has been
detected. This can occur if
either of the following
occurs:
a. the Hydronic Heat Low
Air Temperature Limit input
closes for > 1 second, or
b. the Chilled Water Low Air
Temperature Limit input
opens for > 1 second.
Check: Proper outside air
damper actuator/linkage
setup.
An Information Only
diagnostic is set.
Exhaust Air Bypass Damper
modulated fully closed if
energy recovery for
heating is active or if
energy recovery is not
active. If OA Damper is fully
open Exhaust Air Bypass
and Outside Air Bypass
dampers modulated fully
open when Outside Air
Temp is 10F or less.
The UCM will initiate the
following actions;
a. An "Open All Water
Valves" request is issued to
the heat module function,
causing any steam, hot
water, or chilled water
valves on the unit to open.
b. An "All Heat OFF" request
is issued to the heat control
function.
c. A "Fan Off" request is
sent to the supply fan and
the return fan control
functions.
d. A "Close Damper"
request is sent to the
outside air damper control
function.
(PAR) An automatic reset
occurs after the difference
in the entering and leaving
evaporator temperature is
less than the Evaporator
Temperature Differential
Setpoint minus 5 F.
(PAR) An automatic reset
occurs after the Leaving
Recovery Exhaust Temp
input returns to within
range continuously for 10
seconds
(PMR) A manual reset is
required after the Low Air
Temperature Limit Trip
condition clears. The
Diagnostic can be reset at
the unit mounted Human
Interface, by Tracer, or by
cycling power to the RTM.
RT-SVP07B-EN