Trane RT-SVX38C-EN, Installation, Operation And Maintenance Manual

Page: 40 / 48

Troubleshooting
40 RT-SVX38C-EN
Resetting Lockouts—Method 2
To reset the system at the unit, cycle the unit power by
turning the disconnect switch to OFF and then to ON.
Lockouts can be cleared through the building
management system. Refer to the building management
system instructions for more information.
Zone Temperature Sensor (ZTS)
Service Indicator
The ZSM SERVICE LED is a generic indicator that will
signal the closing of a Normally Open switch at any time,
providing the Indoor Motor (IDM) is operating. This
indicator is usually used to indicate a clogged filter or an
air side fan failure.
The RTRM will ignore the closing of this Normally Open
switch for 2 (±1) minutes. This helps prevent nuisance
SERVICE LED indications. The exception is the LED will
flash 40 seconds after the fan is turned to ON if the Fan
Proving Switch is not made.
Clogged Filter Switch
This LED will remain lit the entire time that the Normally
Open switch is closed. The LED will be turned off
immediately after resetting the switch (to the Normally
Open position), or any time that the IDM is turned to OFF.
If the switch remains closed, and the IDM is turned to ON,
the SERVICE LED will be turned to ON again after the 2 (±1)
minute ignore delay.
This LED being turned to ON will have no other affect on
unit operation. It is an indicator only.
Fan Failure Switch
When the “Fan Failure” switch is wired to the RTOM, the
LED will remain flashing the entire time the fan proving
switch is closed, indicating a fan failure, and it will shut
down the unit operations.
Condensate Overflow Switch
When the “Condensate Overflow Switch” is closed, a
drain pan overflow condition is indicated, and it will shut
unit operations down.
Zone Temperature Sensor (ZTS)
Test
Note: These procedures are not for programmable or
digital models and are conducted with the Zone
Sensor Module electrically removed from the
system.
Test 1—Zone Temperature Thermistor
(ZTEMP)
This component is tested by measuring the resistance
between terminals 1 and 2 on the Zone Temperature
Sensor. Below are some typical indoor temperatures, and
corresponding resistive values.
Test 2—Cooling Set Point (CSP) and
Heating Set Point (HSP)
The resistance of these potentiometers are measured
between the following ZSM terminals. Refer to the chart
above for approximate resistances at the given setpoints.
Cool SP = Terminals 2 and 3
Range = 100 to 900 Ohms approximate
Heat SP = Terminals 2 and 5
Range = 100 to 900 Ohms approximate
Test 3—System Mode and Fan Selection
The combined resistance of the Mode selection switch and
the Fan selection switch can be measured between
terminals 2 and 4 on the Zone Sensor. The possible switch
combinations are listed below with their corresponding
resistance values.
Test 4—LED Indicator Test, (SYS ON, HEAT,
COOL, and SERVICE)
Method 1
Testing the LED using a meter with diode test function. Test
both forward and reverse bias. Forward bias should
measure a voltage drop of 1.5 to 2.5 volts, depending on
your meter. Reverse bias will show an Over Load, or open
circuit indication if LED is functional.
Method 2
Testing the LED with an analog Ohmmeter. Connect
Ohmmeter across LED in one direction; then reverse the
leads for the opposite direction. The LED should have at
least 100 times more resistance in reverse direction, as
compared with the forward direction. If high resistance in
both directions, LED is open. If low in both directions, LED
is shorted.
Table 12. Cooling setpoint and heating setpoint
Zone Temperature Nominal ZTEMP Resistance
50°F 10.0 C° 19.9 K-Ohms
55 F° 12.8 C° 17.47 K-Ohms
60 F° 15.6 C° 15.3 K-Ohms
65 F° 18.3 C° 13.49 K-Ohms
70 F° 21.1 C° 11.9 K-Ohms
75 F° 23.9 C° 10.50 K-Ohms
80 F° 26.7 C° 9.3 K-Ohms
85 F° 29.4 C° 8.25 K-Ohms
90 F° 32.2 C° 7.3 K-Ohms