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4. SERVICING PROCEDURES
GENERAL LOCATION OF CONTROLS
Fast-
Response
Temperature
Sensor
CONTROL BOX COMPONENT
LOCATIONS MODELS 135 & 180
2-Stage Controller
Relay
Fig.# 8195.1
Ignition Module
(Auto Ignition Only)
23
Fig.# 8195.4
SEQUENCE OF OPERATION
INTERMITTENT IGNITION DEVICE (IID)
Boilers equipped with the IID system will automatically light the pilot burner first and then the main burner, each
time there is a call for heat from the room thermostat. Whenever the room thermostat is calling for heat, the
circulator supplied with the boiler, will be energized and should be running. The ignition control module will also
be energized to initiate the pilot ignition by opening the first main valve (pilot). At the same time, the electronic
spark generator in the module produces a high-voltage spark pulse output that lights the pilot burner. If the pilot burner
does not light, the module will not energize the second main valve and the burners will not light. Ignition spark
continues only until the timed trial for ignition period ends. Then, the module goes into safety shutdown or lockout.
Lockout de-energizes the first main valve operator and closes the first main (pilot) valve in the gas control, stopping
pilot gas flow. The ignition control system must be reset by setting the thermostat below room temperature for one
minute or by turning off power to the module for one minute. When the pilot flame is established, flame rectification
circuit is completed between the sensor and burner ground. The flame sensing circuit in the module detects the flame
current, shuts off the spark generator and energizes the second main valve operator which opens the second main
valve. This allows gas to flow to the burners where it is ignited by the pilot burner flame. When the thermostat is
satisfied, the valve operators are de-energized shutting off the pilot and main burners, and also the circulator.
C
IRCULATOR
V
ENT SENSOR
B
YPASS VALVE
(
MODELS 135 & 180 ONLY)
B
YPASS LINE
T
EMPERATURE
A
ND PRESSURE GAUGE
2-STAGED CONTROLLER
(MODEL 90 ONLY)
P
RESSURE
R
ELIEF VALVE
R
ELAY
A
DJUSTABLE
H
IGH LIMIT
F
IELD WIRING
C
OMPARTMENT
F
AST RESPONSE
T
EMPERATURE SENSOR
I
GNITION MODULE
(
AUTO IGNITION ONLY)
TRANSFORMER
R
OLL-OUT SENSOR
G
AS VALVE