Thermal Solutions APEX APX425C Installation, Operating And Service Instructions page 127

12
Troubleshooting
Table 12-5: Hard Lockout Codes (continued)
Lockout
Number
27
Interrupted
Air proving switch failed to open.
Airflow
Switch (IAS) ON
27
Interrupted
Air proving switch failed to close.
Airflow Switch
(IAS) OFF
42
AC inputs phase reversed
AC Phase Fault
47 Flame lost at some stage. See
Flame Lost
284
OEM Memory Lost, Honeywell
Memory Reset To
Default Memory Restored
Default
106308-05 - 3/23
(continued)
Condition
display for details.
APEX Installation, Operating, & Service Instructions
Possible Cause
Air proving switch closed before Prepurge.
• Failed air proving switch. Check switch for proper operation.
• Short in limit string wiring
Air proving switch open during Prepurge or Drive Lightoff.
• Check for vent or combustion air pipe blockage.
• Confirm air proving switch hose connected to gas valve outlet
tapping and outlet tapping internal screw is open.
• Loose or defective limit string wiring
• Check control and display connections.
• Verify line voltage frequency and voltage meet specifications.
• Verify 24 VAC transformer functioning properly.
• Gas pressure too low. See minimum on boiler rating label.
• Air-fuel mixture out of adjustment. See System Start-up Section.
• Disconnected or defective flame sensor wire.
• Defective flame sensor.
• Defective gas valve. Before replacing valve, check for 24 VAC at
gas valve connector during trial for ignition.
• Control failure
• Consult factory
• Replace control
127