Troubleshooting
46
RT-SVX26K-EN
Note:
Before resetting Cooling Failures and Heating
Lockouts check the Failure Status Diagnostics by
the methods previously explained. Diagnostics will
be lost when the power to the unit is disconnected.
Method 1
To reset the system from the space, turn the “Mode”
selection switch at the zone sensor to the “Off” position.
After approximately 30 seconds, turn the “Mode”
selection switch to the desired mode, i.e. Heat, Cool or
Auto.
Method 2
To reset the system at the unit, cycle the unit power by
turning the disconnect switch “Off” and then “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 “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 “Off”.
If the switch remains closed, and the IDM is turned “On”,
the SERVICE LED will be turned “On” again after the 2 (±1)
minute ignore delay.
This LED being turned “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 the
unit operations down.
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
Table 19
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
Table 21, p. 47
with their
corresponding resistance values.
Table 19.
Temps and resistance values
Zone
Temperature
Nominal ZTEMP
Resistance (K-
Ohms)
Nominal CSP or HSP
Resistance (Ohms)
(°F)
(°C)
50
10.0
19.9
889
55
12.8
17.47
812
60
15.6
15.3
695
65
18.3
13.49
597
70
21.1
11.9
500
75
23.9
10.50
403
80
26.7
9.3
305
85
29.4
8.25
208
90
32.2
7.3
110
