Troubleshooting
48
RT-SVX26J-EN
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
Table 21, p. 48
with their
corresponding resistance values.
Test 4
LED Indicator Test, (SYS ON, HEAT, COOL &
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.
Method 3
To test LEDs with ZSM connected to unit, test voltages at
LED terminals on ZSM. A measurement of 32 Vdc, across
an unlit LED, means the LED has failed.
Note:
Measurements should be made from LED common
(ZSM terminal 6 to respective LED terminal). Refer
to
Table 20, p. 48
.
Programmable & Digital Zone
Sensor Test
Testing Serial Communication Voltage
1.
Verify 24 Vac is present between terminals J6-14 and
J6-11.
2. Disconnect wires from J6-11 and J6-12. Measure the
voltage between J6-11 and J6-12, should be about
32 Vdc.
3. Reconnect wires to terminals J6-11 and J6-12. Measure
voltage again between J6-11 and J6-12, voltage should
flash high and low every 0.5 seconds. The voltage on
the low end will measure about 19 Vdc, while the
voltage on the high end will measure from
approximately 24 to 38 Vdc.
4. Verify all modes of operation, by running the unit
through all of the steps in the “Test Modes” section
discussed in
“Start Up,” p. 38
”.
5. After verifying proper unit operation, exit the test
mode. Turn the fan on continuously at the ZSM, by
pressing the button with the fan symbol. If the fan
comes on and runs continuously, the ZSM is good. If
you are not able to turn the fan on, the ZSM is
defective.
ReliaTel Refrigeration Module (RTRM)
Default Chart
If the RTCI loses input from the building management
system, the RTRM will control in the default mode after
approximately 15 minutes. If the RTRM loses the Heating
and Cooling setpoint input, the RTRM will control in the
default mode instantaneously.
The temperature sensing thermistor in the Zone Sensor
Module is the only component required for the “Default
Mode” to operate.
Table 20. Default operation for mechanical ZSM (CV
only)
J6 Input/Connection
If no input/connection this
happens
J6-7
(a)
- Heat indication
(a)these connections are only on certain model ZSMs
LED will not come on while heating
LED will not flash during heat fail
J6-8
(a)
- Cool indication
LED will not come on while cooling
LED will not flash during cool fail
(a)
J6-9
(a)
- System indication
(sys on)
LED will not come on while unit has power
J6-10
(a)
- Service
indication
LED will not come on when CFS or FFS
trips
Table 21.
System mode and fan selection
Resistance
Valves
(K-Ohms)
Zone Sensor
Unit/Fan
Mode
Local Unit
Mode
Local Fan
Mode
2.32
Off/Auto
Off
Auto
4.87
Cool/Auto
Cool
Auto
7.68
Auto/Auto
Auto
Auto
10.77
Off/On
Off
On
13.32
Cool/On
Cool
On
16.13
Auto/On
Auto
On
19.48
Heat/Auto
Heat
Auto
27.93
Heat/On
Heat
On
35.0
Emergency
Heat/Auto
Emergency
Heat
Auto
43.45
Emergency
Heat/On
Emergency
Heat
On
Out of Range
(Short)
INVALID/Short
Invalid (CV),
Auto (VAV)
Invalid
Out of Range
(Open)
INVALID/Open
Invalid (CV), Off
(VAV)
Invalid
Table 21.
System mode and fan selection
