Harsco Industrial C1500H Installation & Owner's Manual page 52

5.6.6 Low Air
If the display panel indicates Locking A34 AIR SWITCH NOT OPEN or Locking A35 AIR SWITCH NOT CLOSED this
indicates improper airflow through the boiler. Check the hoses leading to the air switches. Verify proper blower
operation. An air switch error does not necessarily mean that the air switch is defective.
When A34 AIR SWITCH NOT OPEN is shown on the display, check that the air switch is open when the fan is off.
Check that there is no air flow through the boiler when the fan is off. Check for too much negative within the vent or a
blower that has failed running when it should not be.
When A35 AIR SWITCH NOT CLOSED is shown on the display, check that the air switch is closed when the fan is
running. If the air switch does not close within 5 minutes during purge, the boiler locks out. Check that the burner,
heat exchanger and condensate trap is clean ("Cleaning the Burner," Section 5.2) and that there are no obstructions
to airflow in the intake or exhaust ducts.
5.6.7 Flame Failure
In the event of a flame failure, the main fuel valves are de-energized and a manual reset lockout occurs.
Locking A01 IGNITION FAILURE or Lockout A02 FLAME FAILURE is shown on the display. The cause of flame
failure must be diagnosed and repaired before the control is reset.
When A01 IGNITION FAILURE is shown on the display, the boiler did not light during a trial for ignition. Check that
the spark, electrode, ignition wire, and gas valve are functioning properly.
When A02 FLAME FAILURE is shown on the display, the boiler lost the flame during run. Check that the combustion
is setup properly, the gas pressure is correct, as well as other combustion parameters.
5.6.8 Flame Error
Locking A19 LATE FLAME
Blocking E20 FALSE FLAME
These errors signify flame error. This may be caused by a failed or leaky gas valve or a flame detector malfunction. If
gas valve leakage is suspected, the unit must be isolated by turning off the main gas supply line. Qualified and
knowledgeable service personnel must be called to evaluate and repair/replace the failed parts. Verify that the igniter
cable is not grounding out or there are any cracks within the electrode creating a short circuit.
5.6.9 Stack Problem
E34 BLOCKED_FLUE_indicates that the high exhaust back pressure switch has tripped. This may be caused by a
blocked stack, a blocked air inlet, or a blocked condensate system or a high negative within the vent. When the
blockage is removed, the boiler will automatically restart.
A comprehensive listing of the locking and blocking error codes is provided on the next page.
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MACH Gas Fired Boiler