750-96 (revised 2010)
Model CB Packaged Boiler Manual
1-23
1.18 — Modulating Firing
A feature designed into the circuitry is that the modulating motor must be in the low fire position during ignition
and remain there until the main flame is established. A low fire switch, integral to the motor, is actuated by the
rotation of the motor. The switch must be closed to establish that the damper and fuel metering valves are in low
fire position before the programmer commences into the ignition period. During this time, neither the manual
flame control nor the modulating control have any control over the damper motor, regardless of their settings.
An optionally equipped boiler has a second integral switch used to establish that the motor has driven the
damper to an open position during the pre-purge period. This switch closes, as high fire position is approached,
to complete an internal circuit in the programmer and allow continuation of the programming cycle.
Courtesy of: C3 Surplus LLC
Surplus Industrial Superstore
305-428-2777
https://www.c3surplus.com
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