MACH® Series
Gas-Fired Boiler
37
5.6.2
Loss of Water Level
The low water switch opens when there is insufficient water level in the boiler. Lockout LOW WATER LEVEL
is
shown on the display, the burner operation is interrupted, and the boiler locks out. When the correct water level is re-
established, and the control reset button is pressed, the boiler will reset and will start the sequence at Step 4.
5.6.3 Low
Gas
Pressure
The low gas pressure switch opens when there is (or has been) insufficient gas pressure available for proper
operation of the boiler. If an external gas-supply shut-off valve is closed for any reason, a low gas condition will result.
Locking LOW GAS PRESSURE is shown on the display, the burner operation is interrupted, and the boiler locks out.
When proper gas pressure is restored, and the control reset button is pressed, the boiler will reset and will start the
sequence at Step 4.
5.6.4
High Gas Pressure
The high gas pressure switch opens when there is (or has been) excessive gas pressure for the proper operation of
the boiler Locking HIGH GAS PRESSURE is shown on the display, the burner operation is interrupted, and the boiler
locks out. When proper gas pressure is restored, and the control reset button is pressed, the boiler will reset and will
start the sequence at Step 4.
5.6.5 High
Water
Temperature
When the boiler water has exceeded both the operating and high-limit temperature the high limit switch opens, and
Locking HIGH LIMIT
is shown on the display. When the water temperature falls below the high-limit temperature, the
boiler will remain locked out until the water high limit switch is manually reset and the front panel reset button is
pressed. Once reset, the control will restart the sequence of operation at Step 4.
5.6.6 Low
Air
If the display panel indicates Locking AIR SWITCH NOT OPEN
or Locking 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
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.
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 ("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
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, the gas pressure is correct, as well as other combustion parameters.
5.6.8 Flame
Error
Locking LATE FLAME
Blocking FALSE FLAME
