Cleaver-Brooks CBH 40 - Page 13

OPERATING LIMIT PRESSURE CONTROL
Steam Boiler (Figure 1-2)
OPERATING LIMIT TEMPERATURE CON-
TROL - Hot Water Boiler (Figure 1-3)
Breaks a circuit to stop burner operation on a rise
of boiler pressure or temperature above a selected
setting. It is adjusted to start or stop the burner at
a pre-selected pressure or temperature setting.
HIGH LIMIT PRESSURE CONTROL
Steam Boiler (Figure 1-2)
HIGH LIMIT TEMPERATURE CONTROL
Hot Water Boiler (Figure 1-3)
Breaks a circuit to stop burner operation at a pre-
selected pressure or temperature above the opera-
ting limit control setting. This control must be
manually reset to restore the circuit.
HIGH-LOW FIRE CONTROL (Figures 1-2 & 1-3)
A pressure or temperature control which, when
placed into the circuit by proper setting of the
damper positioning switch, makes or breaks the
circuit to the damper motor causing the burner to
Chapter !-General Description and Principles of Operation
operate at either high or low fire rate in accord-
ance with load requirements.
MODULATING CONTROL (Figure 1-2)
Senses changing boiler pressures, or temperatures,
and transmits this information to the modulating
damper motor to change the firing rate. Provided
only as optional equipment for a gas fired boiler.
When installed on a 200 Series boiler, it is re-
moved from the operating circuitry while the boiler
is fired on oil.
LOW WATER CUT-OFF AND PUMP CONTROL
(Steam Boiler) (Figure 1-2)
This float-operated control responds to the water
level in the boiler. It performs two distinct func-
tions:
(a) Stops firing of the burner if water level lowers
below the safe operating point and low water light
in the control panel; also causes low water alarm
bell (optional equipment) to ring. Code require-
ments for some models require a manual reset type
of low water cutoff. This type requires manual
OPERATING TEMPERATURE,
HIGH LIMIT TEMPERATURE
AND HIGH-LOW FIRE
CONTROLS
FIGURE 1-3. TYPICAL HOT WATER BOILER AND CONTROLS
1-5