Q3 & Qht Controls for Chilled Water Systems Summary of Fault Codes and Indicator Codes
L-2962 ENGLISH 13
SUMMARY OF FAULT CODES AND INDICATOR CODES
INITIAL SYSTEM START UP
1. Turn on the circuit breaker for the air handler.
2. Set the system for RUN Mode.
3. Use the control to set the system for cooling or heating and adjust the set point temperature so the unit will turn on.
4. Verify that there is steady airflow out of the supply-air grille.
5. Allow unit to run for ten minutes at high fan speed. Check the temperature differential between discharge and return air
by placing an accurate thermometer in front of the discharge grill and then in front of the return air grill.
In Cool Mode the difference between the discharge and return should be 15 - 20°F (8.3 - 11.1°C), with normal ambient
air and water temperatures.
In Heat Mode the differential can be as high as 25°F (13.9°C).
If the unit does not appear to be operating properly, refer to the guidelines in “TROUBLESHOOTING” on page 14.
Table 5: Fault-Code and Indicator-Code Descriptions and Results
Code Description Result
IL / - - The air handler’s entering loop water sensor has failed open or shorted. To reset, press
the MODE button (Q3) or POWER button (Qht)
No Operation
- - (flashing) Display connected to SMXII unit. The two components are not compatible. No Operation
IS / - - or - - Inside temperature sensor failure flashes IS / - - for 3 seconds if MODE button is
pressed. After 3 seconds, display shows constant - -. Run Mode may be selected for
emergency operation and display will show a constant - -.
Emergency Operation
Ar / FL Display flashes Ar / FL for 15 seconds every 30 minutes indicating return air filter needs
to be cleaned or replaced. Reset and stop flashing by pressing the FAN, UP, and
DOWN buttons simultaneously.
Continue Operation
LC LC flashes momentarily if a button is pressed indicating the display is locked in current
mode of operation. Enter or exit lock mode by pressing the MODE, UP, and FAN
buttons simultaneously. UL flashes for 3 seconds when exiting lock mode.
Continue Operation
OU or Outside
/ 1st digit / 2nd
2 digits or OU
or Outside / - -
Displays the optional outside temperature as OU (Q3) or Outside (Qht) then the first
digit followed by second two digits. Displays OU or Outside / - - if optional outside
temperature sensor is not installed or failed open or shorted. See “Button Functions” on
page 5 for instructions.
Continue Operation
IL or Water
/ 1st digit / 2nd
2 digits
Displays supply (input) loop water temperature at air handler as IL (Q3) or Water (Qht)
then the first digit followed by second two digits. See “Button Functions” on page 5 for
instructions.
Continue Operation
OL / 1st digit
/ 2nd 2 digits
or OL / - - and
Water
Displays optional return (output) loop water temperature at air handler as OL (Q3) or
OL and Water (Qht) then the first digit followed by second two digits. See “Button
Functions” on page 5 for instructions. Displays OL or Water / - - if optional return loop
water temperature sensor is not installed or failed open or shorted.
Continue Operation
HS / 1st 2
digits
or HS / - -
Displays the optional relative humidity as HS / then the first two digits of relative
humidty. Displays HS / - - if optional humidity sensor is not installed or failed open or
shorted. See “Button Functions” on page 5 for instructions
Continue Operation
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