49
5. Johnson EI Sequence of Operation
a. Normal Operation
i. Thermostat or operating control calls for
heat. Vent Damper (if used) opens.
ii. Ignition Module Terminals 1, GND and the
Ignition Terminal are energized. Terminals 1
and GND power the Pilot Valve in the Gas
Valve supplying as 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 J991 Pilot
Burner and the IGNITION MODULE proves
the presence of the Pilot Flame electronically
and the Ignition Terminal is de-energized.
iv. Terminals 3 and GND 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, 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 J991 Electronic Pilot, after
ignition of pilot flame will close the main gas
valve.
– For approximately 90 seconds after failure
of the J991 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 1 and GND 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 Pages 72 and 73.
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