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B. Safety and Operating Controls. Operation and Shut Down
Component
Circuit Board Fuse
Power Switch
Operating Aquastat
Manual Reset High
Limit Aquastat
Flow Switch
Pressure (Safety)
Relief Valve
Mixer Fuseable Link
Vestibule Fuseable
Link
High and Low Gas
Pressure Switches
Combustion Air Flow
Switch
Flame Safeguard
Control
Variable Frequency
Drive (VFD)
Thermal Solutions
Sage Boiler Control™
(SBC)™
Function
If the power draw of the control circuit exceeds approximately 5 amps, the circuit board
fuse trips and prevents the boiler from operating until the fuse is replaced.
If this switch is in the off position, power is interrupted to the control circuit of the boiler,
which prevents the boiler from operating. If the switch is in the on position, power is sup-
plied to the control circuit.
If the boiler water temperature exceeds the adjustable set point, power is interrupted to the
control circuit of the boiler, which prevents the boiler from operating. When the boiler wa-
ter temperature drops below the set point minus the adjustable differential setting, power is
again supplied to the control circuit.
If the boiler water temperature exceeds the adjustable set point, power is interrupted to the
control circuit of the boiler, which prevents the boiler from operating. Power is interrupted
until the control is manually reset by pressing the control's reset button. When the button
is depressed, power will again be supplied to the control circuit.
If the water flow through the boiler drops below the fixed flow rate required to move the
control's paddle enough to close the controls contacts, power is interrupted to the control
circuit, which prevents the boiler from operating. When the water flow rate is increased,
the paddle closes the control's contacts and power is supplied to the control circuit.
If the pressure inside the appliance exceeds the fixed set point, the valve opens mechani-
cally and discharges water. The valve remains open until the pressure inside the appliance
drops below the set point.
If the temperature in the interior of the burner exceeds the fixed set point. The contacts of
the switch open and power is interrupted to the control circuit, which prevents the boiler
from operating. Power is interrupted until the switch is replaced.
If the temperature in the interior of the vestibule enclosure exceeds the fixed set point, the
contacts of the switch open and power is interrupted to the control circuit, which prevents
the boiler from operating. Power is interrupted until the switch is replaced.
If the gas pressure reaches a point below the adjustable set point, or above the adjustable
set point, the contacts of the switch open and power is interrupted to the control circuit,
which prevents the boiler from operating. Power is interrupted until gas pressure is be-
tween the high and low set points and the control is manually reset by moving the switch to
the reset position. The switches will not reset until the gas pressure is within the set point
parameters.
If the differential air pressure drops below the fixed set point, the contacts of the switch
open and power is interrupted to the control circuit, which prevents the boiler from operat-
ing. Power is interrupted until air flow increases so that the contacts close.
Refer to the manual supplied with the boiler.
The variable frequency drive's primary function is to vary the rotational speed of the blower
fan based on the air requirements of the boiler combustion process. The VFD on Modulat-
ing boilers responds to a 0-10 VDC or 4-20 ma signal from the Digital Temperature Control-
ler.
The Thermal Solutions Sage Boiler Control™ (SBC™) is a complete boiler and automa-
tion system. It provides advanced boiler modulation control, operating control, diagnostics,
multiple boiler lead lag and auxiliary device control. Refer to the SBC manual shipped with
the boiler to learn more about these features and functions.
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