Finned copper tube gas boilers & water heaters – Boiler Manual
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Demand Satisfied:
1. Stage switch 1 opens, TDR1 de-energizes and the N.O. contact
“TDR1-1” opens. TDR4 also de-energizes but the N.O. contact
“TDR4-1” remains closed.
2. Power is removed from FSM closing the main shutoff valve, pilot
valve, and main valve. The blower and power venter shut off when
“K4-1” and “K4-3” open.
3. All indicators are off except “power ”.
4. The pump time delay relay TDR4 initiates a pump post purge
time period (adjustable from 0.1-10 minutes). At the end of the
timed period the N.O. contact “TDR4-1” opens and the pump
then shuts off.
ALARMS
Control
Stage controller alarms are visible on the controller’s LCD screen.
Alarm terminals are visible on the “Limit/Alarm Terminal Strip”
are available to provide an audio or visual indication of faults.
High Limit, Low Water Flow, Low & High Gas Pressure,
Power Venter Interlocks
The gas valves, the blower and power venter will shut off if any
interlock is tripped. The pump will cycle on and off via action of
the stage controller. Condition indicators are visible on the control
panel.
Low Air
The pressure switch will monitor blower air flow. Air monitoring
will begin at prepurge. If a low air condition is present, power will
not be supplied to FSM. Sufficient air flow is required to close the
N.O. contact. Under a low air condition the N.C. contact on this
switch will remain closed energizing the “low air” indicator on the
control panel. The blower will remain on.
OPERATION SEQUENCE, 2-STAGE
D400 THROUGH D900
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
24VAC to the ignition control.
5. K2 will switch the pilot valve, main valve and blower to the
high or low fire mode, depending on the staging control input.
Ignition Trial:
1. Once energized, the flame sense module (FSM) initiates 4 second
diagnostic cycle before sending 24VAC to the PV terminal and
energizing the ignition transformer.
2. The flame failure LED will be lit during the 4 second diagnostic
cycle unless the unit is configured 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.
6. If the second ignition attempt is unsuccessful the gas valves will
lockout, but the blower, pump and power venter will remain
on. To reset the boiler/water heater, take one of the following
steps:
• Adjust the high limit down below the point at which the
blower shuts down, then reset the limit to its normal setting.
• Remove power from the boiler/water heater, wait 30 seconds
and re-establish power to the unit.
7. On CSD-1 applications the blower and power venter will shut
down and the boiler/water heater will lock out. The unit must
be manually reset.
Main Burner:
1. Once the pilot is proved the MV terminal on (FSM) is energized
sending 24VAC to the main gas valve.
2. The main gas valve opens via action of K1.
3. The main burner indicator light illuminates. The PV terminal
remains energized and the pilot indicator remains on.
