30
MODGAS-X Technical Guide
Troubleshooting Alarms
Mechanical Failure:
NOTE:
This alarm was removed in version 3.06.
• Check relay outputs on the MODGAS-X for 24 VAC
output.
• Verify the SAT OPTIONS jumper settings on the
MODGAS-X for Supply Air Temperature Sensor.
• Verify output voltage (VOUT and GND) to gas valve.
• Try forcing valves (refer to the Force Screens,
page 24
).
• Verify that the Supply Air Temperature Sensor is
connected to SAT and GND on the MODGAS-X
(Stand-Alone Mode and when using VAV/CAV or
MUA controller) or to AI2 and GND or AI3 and GND
on the AAON unit controller (Communications Mode).
• Verify Supply Air Temperature Sensor probe is mounted
correctly in supply duct.
• Remove SAT and GND wiring from the MODGAS-X
and ohm the sensor out (this may indicate open or failed
wiring). Refer to
Table 8, page 31
and
Table 9, page 32
.
Supply Air Temperature Failure:
• Verify that the Supply Air Temperature Sensor is
connected to SAT and GND on the MODGAS-X (Stand-
Alone Mode or when using retrofit applications) or to
AI2 and GND or AI3 and GND on specific AAON unit
controllers (Communications Mode).
• Remove SAT and GND wiring from MODGAS-X and
ohm the sensor out (this may indicate open or failed
wiring). Refer to
Table 8, page 31
and
Table 9, page 32
.
• Verify the SAT OPTIONS jumper settings on the
MODGAS-X for the Supply Air Temperature Sensor.
See Table 11, page 34
.
Sat Cutoff Mode:
• Remove SAT and GND wiring from the MODGAS-X
and ohm the sensor out (this may indicate open or failed
wiring). Refer to chart in back of guide for readings.
• With Supply Air Sensor disconnected from the
MODGAS-X, set volt meter to DC volts and measure
voltage between SAT and GND on board. Refer to
Tables 8 and 9, pages 31 and 32
for readings.
• Verify Supply Air Temperature Sensor reading in duct
with third-party temperature testing device.
Communications Loss:
• Check COMM LED on MODGAS-X.
• Verify 24 VAC power to all interconnected AAON unit
controllers and modules.
• Verify connection between the MODGAS-X and
associated AAON unit controllers.
• In Communications Mode (connected to an AAON
unit controller with modular cable), confirm the AAON
unit controller’s MODGAS-X Status Screen displays
MODGAS-X’s Supply Air Temperature and the Main
MODGAS-X Screens show COMM MODE.
TROUBLESHOOTING
Alarms
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