Burnham Independence IN10 - Manual (Page 31)

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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.
H. Steam Boiler with Continuous Ignition (Standing Pilot)
and Probe Low Water Cutoff. See Figure 35.
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.