RBI DOMINATOR Series - Electrical Wiring and Operation; Electrical Wiring; Hydronic Heating Boilers

Finned copper tube gas boilers & water heaters – Boiler Manual
23
BOILER/WATER HEATER OPERATION
Staging Operation
e Dominator boiler/water heater series is separated into on/o,
2-stage and 4-stage units depending on the model size. e 300 is
on/o only. e 400 through 900 models have two ring inputs. 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 identies the stages and ring modes
associated with the on/o (D300), 2-stage units (D400-D900), and
Table 13 identies the stages and ring modes associated with the
4-stage units (D1050-D2100).
Table 12 Firing Modes (D400-D900) – D300 On/Off Only
Stage Firing Mode
O O
1 Low Fire
2 High Fire
Table 13 Firing Modes (D1050-D2100)
Stage Left Firing Mode Right Firing Mode
O O O
1 Low Fire O
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 re, but left and right
blowers will be on and operating at low re (low speed).
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. e Dominator will stage up or down
progressively, but will not jump over a stage. Stage 1 will operate 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
le 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 airows should be
balanced so that when both sides are at low or high re, stage 2 or 4,
the gas and airows are equal.
Pressure Switch Settings
Dierential pressure switches are provided in the Dominator to shut
down gas ow under a blocked ue or inlet condition. One high re
pressure switch is used for the 300 and one low re and one high re
pressure switch are used for the 400 through 900 models. Two low
re and two high re pressure switches are used for the 1050 through
2100 models. e low re pressure switches serve to shut down gas
ow if there is a blocked ue or inlet condition during low re
operation. Similarly, the high re switches will shut down gas ow if
there is a blocked ue or inlet condition during high re operation.
e di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 dierential pressure readings, Figure 17. Table 14 lists the
dierential pressure seings for all of the models.
Figure 17 Pressure Switch Tap(s)
Table 14 Differential Pressure Settings (All Units)
Model
Dierential Pressure
Requirement at High Fire
(All Units)
Inches WC mm WC
300-900 1.0 ± 0.1 20.3 ± 2.5
1050-2100 1.0 ± 0.1 25.4 ± 2.5
On the 4-stage units, the le low re and high re switches
will interrupt power to the control module under a blocked ue or
inlet condition. is will cause the pilot and le and right main gas
valves to close. e right switches will only shut down the right main
gas valve under a blocked ue or inlet condition. e relay board
automatically selects between pressure switches as the boiler/water
heater changes stages. Tables 15 and 16 identify how pressure switch
control changes during boiler/water heater staging. Tables 17 and 18
identify the control actions if a low air condition occurs at any stage.
For example, when operating at stage 2, the le and right low re
pressure switches monitor the boiler/water heater, since the blowers
are operating at low speed. When the unit stages to stage 3 the le
blower will be switched to high speed and the relay board will switch
the circuit so that the le high re switch monitors the dierential
pressure for the le side. e right low re pressure switch will
continue to control the right side until the unit stages to stage 4.
At that point, the right high re pressure switch will automatically
take over monitoring duties for the right side. A low air condition
in either plenum will cause a red light to illuminate on the indicator
board.