Smith Cast Iron Boilers GT Series - Manual (Page 26)

GT INSTALLATION AND OPERATION INSTRUCTIONS Page 26
Figure 35 - Conventional Mode Operation Chart
T-C & A-C Open T-C Closed & A-C open T-C Closed & A-C Closed T-C Open & A-C Closed
Condition Standby Heating Only Domestic Only Domestic Only
Set Point — HI L0 L0
Burner On — HI - DIF LO-10 LO-10
Burner Off — HI + 10 200°F 200°F
Heat Circ. Off On Off Off
Aux. Circ. Off Off On On
SENTRY 2100T CONTROLLER
CAUTION: The T4.0 controller can only be used
on the GT-400 and the T2.0 on the GT-150 & 200.
Misapplication of the controller will result in
improper boiler operation.
The Sentry 2100T controller is the central controller for
the GT boiler. The Sentry handles all of the combustion
logic, along with the energy management functions.
The Sentry 2100T operates in two different modes,
Conventional or Reset, see Figures 35 & 36. The mode is
automatically determined by the presence of the outdoor
sensor. When the Sentry 2100T detects the presence of
the outdoor sensor the controller will operate in the Reset
Mode. If the outdoor sensor is not installed, the controller
will operate in the Conventional Mode.
NOTE: If the outdoor sensor is connected after the
boiler has been started power to the boiler must be
shut off and then turned back on.
Boiler Modulation
The GT boiler employs a pneumatic modulation system.
This modulation system increases or decreases the
speed of the blower to meet the heating demand. The
gas valve pressure regulator senses the air pressure
and adjusts the gas fl ow to ensure correct combustion.
The term “Set Point” is used to indicate the desired
temperature that the GT will maintain by increasing or
decreasing the input.
Indirect Water Heaters
The Sentry 2100 comes with an input and output for
a 120-volt indirect pump. When the A and C terminals
are closed, dry contact, the boiler will go immediately
to indirect domestic mode, whereby the indirect pump
is activated, and the boiler will modulate to the LO
setpoint.
Sentry Display
The Sentry 2100T contains four green lights that illuminate
to indicate the boilers state of operation, Figure 37.
Figure 37 - 2100T Display Screen
Burner/Bruleur - Indicates that the ignition system is
activated.
Circ. - Indicates that the heating pump is energized.
Circ. Aux.- Indicates a call for DHW, and Indirect pump
or 3-way valve is activated.
Thermostat Demand - Indicates that terminals T-C are
closed, iniating a call for heat.
The LED screen will display one of four values. A light will
illuminate above the function to indicate what information
is being displayed.
Water Temp - Indicates that the display is showing the
boiler water temperature.
Air - if the air sensor is used. When illuminated, indicates
that the display is showing outdoor air temperature.
Gas Input Value - Indicates the current input level. Figure
38 must be used to determine the actual input. GT-150
use 46 to 240, GT-200 use 40 to 240 and GT-400 use
35 to 195.
DHW Temp. - indicates that there is a call for domestic
hot water.
Figure 36 - Reset Mode Operation Chart
T-C & A-C Open T-C Closed & A-C open T-C Closed & A-C Closed T-C Open & A-C Closed
Condition Standby Heating Only Domestic Only Domestic Only
Set Point — HI Calc. L0 L0
Burner On — HI Calc - DIF LO-10 LO-10
Burner Off — HI
Calc
+ 10 200°F 200°F
Heat Circ. (C1) Off On Off Off
Aux. Circ. (Ap) Off Off On On