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33
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 ames or excessive heat
are present in vestibule. Control is single use
device. If ame roll-out switch is activated do
not attempt to place boiler in operation. Correct
source of blockage and replace ame roll-out
switch.
e. Igniter/Sensor: senses pilot ame and causes
ignition module to turn off main burner and pilot
burner gas ow should pilot burner ame
extinguish. Five to six minutes after shutdown,
Ignition Module restarts ignition sequence.
For Electronic Ignition Trouble Shooting Guide,
see Page 65. For LED Status Codes, see Tables
8 and 9 on pages 55 and 56.
I. Steam Boiler with Intermittent Ignition (EI) and Probe
Low Water Cutoff. See Figure 36.
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. Ignition Module is energized. Pilot Valve opens
and Igniter is energized to ignite Pilot Burner.
d. Sensor proves presence of pilot ame. Main
Valve(s) opens and ignites Main Burners.
e. After Thermostat is satised Ignition Module is
de-energized, extinguishing pilot and main
ame. 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