43
Trouble Shooting
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 be-
tween terminals 1 and 2 on the Zone Temperature Sensor.
Below are some typical indoor temperatures, and correspond-
ing resistive values.
Test 2
Cooling Set Point (CSP) and Heating Set Point (HSP)
N o m in a l Z T E M P
R e s is t a n c e
5 0 F °
1 0 .0 C °
1 9 .9 K - O h m s
5 5 F °
1 2 .8 C °
1 7 .4 7 K - O h m s
6 0 F °
1 5 .6 C °
1 5 .3 K - O h m s
6 5 F °
1 8 .3 C °
1 3 .4 9 K - O h m s
7 0 F °
2 1 .1 C °
1 1 .9 K - O h m s
7 5 F °
2 3 .9 C °
1 0 .5 0 K - O h m s
8 0 F °
2 6 .7 C °
9 .3 K - O h m s
8 5 F °
2 9 .4 C °
8 .2 5 K - O h m s
9 0 F °
3 2 .2 C °
7 .3 K - O h m s
Z o n e
T e m p e r a t u r e
The resistance of these potentiometers are measured be-
tween 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 termi-
nals 2 and 4 on the Zone Sensor. The possible switch com-
binations are listed below with their corresponding resis-
tance 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 mea-
sure 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 Ohm-
meter 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 direc-
tions, LED is open. If low in both directions, LED is shorted.
Method 3
To test LED’s 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.
Relative Humidity Sensor Test
This component is measured by measuring the mA output
signal on the Relative Humidity Sensor. Verify accuracy of
the sensor annually. If the output reading is 0 mA, first verify
that power is applied to the sensor. A reading of 4 mA
corresponds to 0% RH and 20 mA corresponds to 100% RH.
% RH
mA
30
8.8
40
10.4
50
12.0
60
13.6
70
15.2
80
16.8
Note: Measurements should be made from LED
common (ZSM terminal 6 to respective LED
terminal). Refer to the Zone Sensor Module (ZSM)
Terminal Identification table at the beginning of this
section.
Programmable & Digital Zone Sensor Test
Testing serial communication voltage
1. Verify 24 VAC is present between terminals J6-14 & J6-
11.
2. Disconnect wires from J6-11 and J6-12. Measure the volt-
age 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
“Unit Start-Up”.
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 sys-
tem, the RTRM will control in the default mode after approxi-
mately 15 minutes. If the RTRM loses the Heating and Cool-
ing setpoint input, the RTRM will control in the default mode in-
stantaneously. The temperature sensing thermistor in the Zone
Sensor Module is the only component required for the “Default
Mode” to operate.