Servicing Procedures, Sequence Operation

SERVICING

PROCEDURES

General Location of Controls

2-Stage Controller

Relay

Fast-

Response Ignition Module

Temperature (Auto Ignition Only)

Sensor

Fig. 25: Control Box Component Locations

Models 135 & 180

CIRCULATOR

VENT SENSOR

BYPASS VALVE (MODELS 135 & 180 ONLY)

BYPASS LINE

TEMPERATURE

AND PRESSURE GAUGE

2-STAGED CONTROLLER (MODEL 90 ONLY)

PRESSURE RELIEF VALVE

RELAY

ADJUSTABLE

HIGH LIMIT

FIELD WIRING

COMPARTMENT

FAST RESPONSE TEMPERATURE SENSOR

IGNITION MODULE

(AUTO IGNITION ONLY)

TRANSFORMER

ROLL-OUT SENSOR

GAS VALVE

Fig. 26: Component Locations

SEQUENCE OF

OPERATION

Intermittent Ignition Device (IID)

Boilers equipped with the IID system will automatical- ly light the pilot burner first and then the main burner, each time there is a call for heat from the room ther- mostat. 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 genera- tor in the module produces a high-voltage spark 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 safe- ty 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 genera- tor 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 burn- er flame.

When the thermostat is satisfied, the valve operators are de-energized shutting off the pilot and main burn- ers, and also the circulator.