MACH
®
Gas Fired Boiler
42
When 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 is
clean (refer to "Cleaning the Burner," Section 5.2) and that there are no obstructions to airflow in the intake or exhaust
ducts.
5.5.7
Flame Failure
In the event of a flame failure, the main fuel valves are de-energized and a manual reset lockout occurs. Locking
IGNITION FAILURE or Lockout FLAME FAILURE is shown on the display. The cause of flame failure must be
diagnosed and repaired before the control is reset.
When 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 FLAME FAILURE is shown on the display, the boiler lost the flame during run. Check that the combustion is
setup properly (see section 3.11), the gas pressure is correct (see section 3.6), as well as other combustion
parameters.
5.5.8
Flame Error
Flame error is indicated by Locking LATE FLAME or Blocking FALSE FLAME. 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.
5.5.9
Blocked Flue
High exhaust back pressure is indicated by BLOCKED FLUE. The cause may be a blocked stack, a blocked air inlet,
or a blocked condensate system. When the blockage is removed, the boiler will automatically restart.