Burnham IN10 Normal Operation, Safety Shutdown, c. Blocked Vent Switch. Automatically interrupts

J.Steam Boiler with Continuous Ignition (Standing Pilot) and Float Low Water Cutoff. See Figure 37.

1.Normal Operation

a.Thermostat calls for heat. Thermostat Isolation Relay is energized, closing contacts.

b.Vent Damper (if used) opens as stated in Vent Damper Sequence of Operation.

c. Gas Valve(s) is energized allowing main gas flow and ignition of Main Burners.

d. After Thermostat is satisfied Gas Valve(s) is de- energized, extinguishing main flame. Vent Damper (if used) closes.

2.Safety Shutdown

a. Limit: Automatically interrupts main burner operation when steam pressure exceeds set point. Maximum allowable pressure is 15 psi. Normal operation resumes when system pressure falls below set point.

b. Low Water Cutoff (LWCO): Automatically interrupts main burner operation when surface of boiler water falls to lowest permissible operating level. Normal operation resumes when water returns to normal level.

c. Blocked Vent Switch. Automatically interrupts

main burner operation when excessive vent system blockage occurs. Control is a multiple use device. If blocked vent switch is activated do not attempt to place boiler in operation. Correct source of blockage and reset blocked vent switch.

d. Flame Roll-out Switch. Automatically interrupts boiler operation when flames or excessive heat are present in vestibule. Control is single use device. If flame roll-out switch is activated do not attempt to place boiler in operation. Correct source of blockage and replace flame roll-out switch.

e. Thermocouple: senses pilot flame and causes gas valve to turn off main burner and pilot burner gas flow should pilot burner flame extinguish.

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