44
4. Honeywell EI Sequence of Operation
a. Normal Operation
i. Thermostat or operating control calls for
heat. Vent Damper (if used) opens.
ii. Ignition Module Terminals PV, MV/PV
and the Ignition Terminal are energized.
Terminals PV and MV/PV power the Pilot
Valve in the Gas Valve supplying gas to the
Pilot. The Ignition Terminal supplies
voltage to the Ignition Electrode creating an
electric spark to ignite the Pilot.
iii. The sensing Circuit between the Q348 Pilot
Burner and the IGNITION MODULE
proves the presence of the Pilot Flame
Electronically and the Ignition Terminal is
de-energized.
iv. Terminals MV and MV/PV of the
IGNITION MODULE are energized and
supply power to the Main Gas Valve. The
Gas Valve is energized allowing main gas
flow, and ignition of Main Burners.
v. Call for heat ends. Ignition module is de-
energized, de-energizing gas valve, and
extinguishing pilot and main flame. Vent
Damper (if used) closes.
b. Safety Shutdown
i. Limit: Automatically interrupts power to
the Ignition Module and Gas Valve(s),
extinguishing pilot and main flame, when
water temperature exceeds set point.
Maximum allowable temperature is 250°F.
Circulator continues to operate with call for
heat, Vent Damper (if used) closes. Normal
operation resumes when water temperature
falls below set point.
ii. Blocked Vent Switch: Automatically
interrupts main burner operation when
excessive flue gas spillage occurs.
Circulator continues to operate and Vent
Damper (if used) remains open with call for
heat. If blocked vent switch is activated do
not attempt to place boiler in operation.
Correct cause of spillage and reset blocked
vent switch.
iii. Flame Roll-out switch: Automatically
interrupts main burner operation when
flames or excessive heat are present in
vestibule. Circulator continues to operate,
Vent Damper (if used) remains open with
call for heat. Control is single use device.
If flame roll-out switch is activated, do not
attempt to place boiler in operation.
Correct cause of spillage and replace flame
roll-out switch.
iv. Pilot
– Pilot failure can occur during the start-up or
the operating cycle of the boiler. Any pilot
failure of the Q348 Electronic Pilot, after
ignition of pilot flame will close the main
gas valve in 0.8 seconds.
– For approximately 90 seconds after failure
of the Q348 pilot, the module through the
ignition terminal will try to reestablish pilot
flame. If no pilot flame can be sensed by
the flame rod circuit, terminals PV and
MV/PV are de-energized and the module
will lock out on safety. Five to six minutes
after shutdown, the IGNITION MODULE
restarts the ignition sequence. The ignition
trial, shutdown, and wait sequence
continues until either the pilot lights or the
Thermostat is set below room temperature
(to end the call for heat). The ignition
sequence can be reset by setting down the
Thermostat for one minute.
c. Trouble Shooting Guide. See Page 71.
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