DOMINATOR INSTALLATION AND OPERATION INSTRUCTIONS
Page 25
OPERATION SEQUENCE, 2 STAGE
D300 THROUGH D900
Note: On Models D1050-2100, 2 stage, factory
jumpers are installed on remote staging terminal
strip to force 2 stage operation. Refer to the included
connection and wiring diagrams for further control
system information.
POWER ON:
Demand for Heat:
1. BTC staging control starts pump and begins 50
second delay before energizing Stage 1.
2. Stage switch 1 closes.
3. System checks primary limit and other interlocks.
Will not start if either switch is open.
Prepurge:
1. TDR1 energizes starting a 40 second prepurge
cycle.
2. K3 energizes the low speed side of the blower. If
the side wall vent option is used the power venter
is energized, closing the power venter interlock. The
power vent indicator light illuminates.
3. The low air indicator light will remain lit until the
blower comes up to speed. The indicator light will
turn off and prepurge indicator light will illuminate
when the pressure switches make.
4. At the end of the prepurge cycle TDR1 times out.
K3 opens and the prepurge indicator light goes out.
K2 closes sending 24V ac to the ignition control.
5. K2 will switch the pilot valve, main valve and blower
to the high or low fi re mode, depending on the
staging control input.
Ignition Trial:
1. Once energized, the fl ame sense module (FSM)
initiates 4 second diagnostic cycle before sending
24V ac to the PV terminal and energizing the
ignition transformer.
2. The fl ame failure LED will be lit during the 4 second
diagnostic cycle unless the unit is confi gured for
CSD-1. When the PV terminal energizes, the LED
will turn off. If the ignition trial fails, the LED will
relight.
3. The pilot valve and ignition transformer are
energized for the 10 second ignition trial. The pilot
indicator light illuminates during this time.
4. If the ignition attempt is unsuccessful, the ignition
module will retry in 5 minutes.
5. Since the staging controller remains powered, it will
continue to stage up for as long as the call for heat
exists. The blower, pump and power venter will
remain for as long as a call for heat exists.
On the four stage units, the left low fire and high fire
switches will interrupt power to the control module under
a blocked fl ue or inlet condition. This will cause the pilot
and left and right main gas valves to close. The right
switches will only shut down the right main gas valve
under a blocked fl ue or inlet condition. The 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 left and
right low fi re pressure switches monitor the boiler/water
heater, since the blowers are operating at low speed.
When the unit stages to stage 3 the left blower will be
switched to high speed and the relay board will switch
the circuit so that the left high fi re switch monitors the
differential pressure for the left side. The right low fi re
pressure switch will continue to control the right side
until the unit stages to stage 4. At that point, the right
high fi 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.
Table 15 -Pressure Switch Control, D300-D2100
Table 16 - Pressure Switch Control, D1050-D2100
Table 17 - Low Air Condition Action, D300-D2100
Table 18 - Low Air Condition Action, D1050-D2100
Stage
Control
Action
1
No Power to Ignition Module
2
No Power to Ignition Module
Stage
Left Side
Right Side
1
No Power to
N/A
Ignition
Module
2
No Power to
No Power to
Igniton
Module Right
Valve
3
No Power to
No Power to
Ignition
Module Right
Valve
4
No Power to
No Power to
Ignition
Module Right
Valve
Stage
Pressure Switch Mode
1
Low
Fire
2
High
Fire
Stage
Pressure Switch Mode
1
Left Low Fire
N/A
1
2
Left Low Fire
Right Low Fire
3
Left High Fire
Right Low Fire
4
Left High Fire
Right High Fire
1
At Stage 1, the right main valve will not be energized.
