CleaverBrooks CB - Hot Water Controls: All Fuels; Controls for Gas Firing

General Description
1-8
750-96 (revised 2010)
Model CB Packaged Boiler Manual
1.7 — Hot Water Controls: All Fuels
1.8 — Controls for Gas Firing
Depending upon the requirements of the insurance carrier or other governing agencies, the gas flow control sys-
tem, or gas train, may consist of some, or all, of the following items.
Control Description
1. Water Temperature
Gauge
Indicates the boiler’s internal water temperature.
2. Water Pressure Gauge Indicates the boiler’s internal water pressure.
3. Operating Limit Tem-
perature Control
Breaks a circuit to stop burner operation on a rise of boiler temperature above a selected
setting. It is adjusted to stop or start the burner at a preselected operating temperature.
4. High Limit Tempera-
ture Control
Breaks a circuit to stop burner operation on a rise of temperature above a selected set-
ting. It is adjusted to stop the burner at a preselected temperature above the operating
control setting. The high limit temperature control normally is equipped with a manual
reset.
5. Modulating Tempera-
ture Control
Senses changing boiler temperature and transmits this information to the modulating
motor to change the burner's firing rate when the manual-automatic switch is set on
automatic.
6. Low Water Cutoff Breaks the circuit to stop burner operation if water level in the boiler drops below a safe
operating point, activating low water light and optional alarm bell if the burner is so
equipped.
7. Auxiliary Low Water
Cutoff (optional)
Breaks the circuit to stop burner operation if the water level in the boiler drops below the
master low water cutoff point.
8. Relief Valve(s) Relief valve(s) relieve the boiler of pressure higher than the design pressure or a lower
pressure, if designated. Relief valves and their discharge piping are to be installed to con-
form to ASME Code requirements.
NOTE: Only the relief valves manufacturer’s representative should adjust or repair the
boiler relief valves.
Control Description
1. Gas Pilot Valve A solenoid valve that opens during the ignition period to admit fuel to the pilot. It closes
after main flame is established. The sequence of energizing and de-energizing is con-
trolled by the programming relay. A second gas pilot valve may be required by insurance
regulations.
2. Gas Pilot Vent Valve When a second gas pilot valve is required, a normally open vent valve is installed
between them. Its purpose is to vent gas to the atmosphere, should any be present in the
pilot line when the pilot valves are closed. The valve closes when the pilot valves are
energized.
3. Gas Pilot Shutoff
Cock
For manually opening or closing the gas supply to the gas pilot valve.
4. Gas Pilot Adjusting
Cock
Provided to regulate the size of the gas pilot flame.