Thermal Solutions APEX APX425C Installation, Operating And Service Instructions page 124

12
Troubleshooting
Table 12-3: Soft Lockout (Hold) Codes (continued)
Lockout
Number
7
Shorted or open return temperature
Return Sensor
Fault
8
Shorted or open supply
Supply Sensor
Fault
9
Shorted or open Domestic Hot
DHW Sensor
Water (DHW) temperature sensor.
Fault
10
Shorted or open flue gas (stack)
Stack Sensor
Fault
13
Flame rod Flame rod shorted to ground
shorted to ground
14
Temperature rise between supply
Delta T Inlet/
Outlet High
15
Return Return temperature was greater
Temperature than supply temperature for at least
Higher Than
Supply
16
Supply Supply water temperature has risen
Temperature
Risen Too Quickly
17
Normal waiting for blower speed to
Fan Speed Not
match purge and light-off setpoint.
Proved
27
Interrupted
Air proving switch failed to open.
Airflow
Switch (IAS) ON
27
Interrupted
Air proving switch failed to close.
Airflow Switch
(IAS) OFF
124
(continued)
Condition
sensor.
temperature sensor.
temperature sensor.
and return is too high.
75 seconds.
too quickly.
APEX Installation, Operating, & Service Instructions
Possible Cause
• Shorted or miswired return sensor wiring
• Defective return sensor
• Shorted or miswired supply sensor wiring
• Defective supply sensor
• Shorted or miswired DHW sensor wiring
• Defective DHW sensor
• Shorted or miswired flue sensor wiring
• Defective flue sensor
• Shorted or miswired flame rod wiring
• Defective flame rod
Inadequate boiler water flow.
• Boiler pump not operating
• Boiler pump undersized
• Valve closed
• Reversed flow through boiler. Verify correct piping and circulator
orientation.
• No boiler water flow. Verify system is purged of air and
appropriate valves are open.
• Defective supply or return sensor
Inadequate boiler water flow. See also causes for Hard Lockout 4.
• Boiler pump not operating
• Boiler pump undersized
• Valve closed
N/A
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
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