Adjustment Procedures
6-8
750-91 (revised 2009)
Model CB-LE Packaged Boiler Manual
In the setting of the controls, consideration must be given to the time required for a burner restart. Each start,
requires a pre-purge period, plus the fixed time required for proving the pilot and main flame. In addition, approx-
imately one-half minute is required for the damper motor to travel from low to high-fire. The time lag may allow
pressure or temperature to drop below desirable limits.
6.6 — Modulating Pressure Control: Steam
Turn the adjusting screw until the indicator is opposite the low point of the desired modulating range. Modulated
firing will range between the low point and a higher point equal to the modulating range of the particular control.
• in 0 - 5 psi controls the range is 1/2 lb
• in 5 - 150 psi controls the range is 5 lbs
• in 10 - 300 psi controls the range is 12 lbs
6.7 — Operating Limit Pressure Control: Steam
Set the “cut-out” (burner off) pressure on the main scale using the large adjusting screw. Set the differential on the
short scale by turning the small adjusting screw until the indicator points to the desired difference between cut-out
and cut-in pressures. The “cut-in” (burner on) pressure is the cut-out pressure minus the differential. The cut-out
pressure should not exceed 90% of the safety valve setting.
6.8 — High Limit Pressure Control: Steam
Set the “cut-out” (burner off) pressure on the main scale using the adjusting screw. The control will break a circuit
when pressure reaches this point. The setting should be sufficiently above the operating limit pressure control to
avoid shutdowns, and preferably not exceed 90% of safety valve setting. The control requires manual resetting after
tripping on a pressure increase. To reset, allow pressure to return to normal and then press the reset button.
6.9 — Modulating Temperature Control: Hot Water
Turn the knob on the front of the case until the pointer indicates the desired setpoint temperature. The desired set-
point is the center point of a proportional range. The control has a 3º to 30º differential and may be adjusted to
vary the temperature range within which modulating action is desired.
To prevent burner shutdown at other than low-fire setting, adjust the modulating pressure control to modulate to low-
fire BEFORE the operating limit pressure control shuts off the burner. Failure to follow these instructions could result
in damage to the equipment.
!
Caution
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