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Finned copper tube gas boilers & water heaters – Boiler Manual
24
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BOILER/WATER HEATER OPERATION
Staging Operation
Th e Dominator boiler/water heater series is separated into 2-stage
and 4-stage units depending on the model size. Th e 300 through 2100
models have two fi ring inputs. Th e 1050 through 2100 have four.
Input staging is controlled from the staging controller that signals the
relay board to select the blower and gas valve modes. Table 12
identifi es the stages and fi ring modes associated with the 2 stage units
(D300-D2100), and Table 13 identifi es the stages and fi ring modes
associated with the 4 stage units (D1050-D2100).
Table 12
Firing Modes (D300-D2100)
Stage
Left Firing Mode
Off
Off
1
Low Fire
2
High Fire
Table 13
Firing Modes (D1050-D2100)
Stage
Left Firing Mode
Right Firing Mode
Off
Off
Off
1
Low Fire
Off
1
2
Low Fire
Low Fire
3
High Fire
Low Fire
4
High Fire
High Fire
1- The left main valve will operate at low fi re, but left and right
blowers will be on and operating at low fi re (low speed).
Th e outlet water temperature is automatically controlled by the
staging controller. It utilizes inputs from the inlet and outlet water
temperature sensors, plus optional tank and outside sensors, to stage
the boiler/water heater. Th e Dominator will stage up or down
progressively, but will not jump over a stage. Stage 1 will operate fi rst,
last and whenever the boiler/water heater is in operation. Consult
the staging controller documentation for further information on
controller operation.
For the D1050-D2100, the air inlet plenum is divided into
left and right sides. A separate blower, main gas valve and manifold
are used for each side. However, the combustion chamber is
undivided. For best overall performance, gas and airfl ows should be
balanced so that when both sides are at low or high fi re, stage 2 or 4,
the gas and airfl ows are equal.
Pressure Switch Settings
Diff erential pressure switches are provided in the Dominator to shut
down gas fl ow under a blocked fl ue or inlet condition. One low fi re
and one high fi re pressure switch are used for the 300 through 900
models. Two low fi re and two high fi re pressure switches are used
for the 1050 through 2100 models. Th e low fi re pressure switches
serve to shut down gas fl ow if there is a blocked fl ue or inlet condition
during low fi re operation. Similarly, the high fi re switches will shut
down gas fl ow if there is a blocked fl ue or inlet condition during high
fi re operation.
Th
e diff erential pressure is taken between the
air plenum and the pressure inside one of the main burners.
Pressure taps are provided in the control compartment for taking
the diff erential pressure readings, Figure 17. Table 14 lists the
diff erential pressure sett ings for all of the models.
Figure 17
Pressure Switch Tap(s)
Table 14
Differential Pressure Settings (All Units)
Model
Differential Pressure
Requirement at High Fire
(All Units)
Inches W.C.
mm W.C.
300-900
1.0 ± 0.1
20.3 ± 2.5
1050-2100
1.0 ± 0.1
25.4 ± 2.5
