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MACH® Series
Gas-Fired Boiler Maintenance
Page 33
Loss of Water Level
The low water switch opens when there is insufficient
water level in the boiler. E 12 is shown on the display,
and burner operation is interrupted. When the correct
water level is re-established, pushing the reset button
will return the sequence to Step 5, provided that the
other limits are satisfied.
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; E 12 is shown on the display,
and burner operation is interrupted. If a gas-supply
shut-off valve is closed for any reason, a low gas
condition will result.
When gas pressure is restored, E 12 will remain on the
display panel, and the boiler will remain locked out
until the front panel reset button is pressed.
Once the control is reset, the sequence returns to Step
5, provided that the other limits are satisfied.
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. An E 12 service code is
displayed and the burner operation is interrupted.
When proper gas pressure is restored, E 12 remains on
the display with the boiler locked out until the front
display panel reset button is pressed.
High Water Temperature
When the boiler water has exceeded both the operating
and high-limit temperature the high limit switch opens,
and E 12 is shown on the display. When the water
temperature falls below the high-limit temperature, the
boiler will remain locked out until the switch is
manually reset and the front panel reset button is
pressed. Once the switch, and the front panel are reset,
the sequence returns to Step 5, provided that the other
limits are satisfied.
Low Air
If the display panel indicates E 08 this indicates
insufficient airflow through the burner. 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. A low air indication does not
necessarily mean that the low air switch is defective.
Air Switch Closed
If the display panel indicates B 61 this indicates the air
pressure switch did not open when the blower was shut
off. Check that there is no air flow through the boiler
when the fan is off. If there is no hidden source of air
flow, replace the switch.
Flame Failure
In the event of a flame failure during a firing period or
a trial for ignition, the main fuel valves are de-
energized and a manual reset lockout occurs. After the
spark ignition is re-energized, the 3 second trial-for-
ignition begins again. If flame failure occurs during a
trail-for-ignition, a safety lockout occurs. The display
will indicate E 02. If flame failure occurs and an
service code is displayed, the combustion control must
be manually reset.
E 00 signifies a leaky gas valve. In the event of a false
flame signal E 00 fault code is indicated. This fault
code could indicate a gas valve failure or leakage of
the gas valve. If gas valve leakage is suspected, the
unit must be isolated by turning off the main gas
supply line until the gas valve is replaced.