CleaverBrooks CBLE, Operation And Maintenance Manual

Page: 93 / 194

750-91 (revised 2009)
Model CB-LE Packaged Boiler Manual 6-5
6.5 — Burner Operating Controls: General
6.5 — Burner Operating Controls: General
The standard boiler operating control package consists of three separate controls.
1.
High Limit Control: Senses the hot water temperature or steam pressure. It is used as a safety limit to turn the
burner off in the event the operating limit control fails. The high limit control should be set sufficiently above
the operating limit control to avoid nuisance shutdowns.
2.
Operating Limit Control: Senses temperature or pressure and automatically turns the burner on to initiate the
startup sequence when required and turns the burner off to initiate the shutdown sequence when the demand is
satisfied. The control must be set to initiate startup only at the low-fire position.
3.
Modulating Control: Senses changes in the hot water temperature or steam pressure and signals the modulat-
ing motor to control the flow of fuel and air to the burner. With either steam or hot water boilers, the modulat-
ing control must be set to ensure the burner is at its minimum low-fire position before the operating limit
control either starts or stops the burner.
When adjusting or setting controls, first be sure all control devices are securely mounted and level. With the tem-
perature sensing control, make sure the sensing bulb is properly bottomed in its well and is secured against move-
ment. Be sure the connecting tubing is not kinked.
The dial settings are generally accurate, although it is not unusual to have a slight variation between a scale setting
and an actual pressure gauge or thermometer reading. Always adjust the control setting to agree with pressure
gauge or thermometer readings. Accurate instrument readings are required. When necessary use auxiliary test
equipment to set controls.
Burner controls correctly set to match load demands will provide operational advantages and achieve the following
desirable objectives:
•
The burner will be operating in low-fire position prior to shutdown.
•
The burner will operate at low-fire for a brief period on each start during normal operation.
•
Elimination of frequent burner on-off cycling.
NOTE: Adjustments to the boiler operating controls should be made by an authorized Cleaver-Brooks Service Tech-
nician. Refer to the appropriate boiler operation and maintenance manual for specific information on boiler startup
and operation.