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BOILER CONTROL: INTERNAL WIRING & OPERATION
Figure 8.6 shows a typical ignition and burn cycle for
the Series
PFC™
boiler. Pre-purge and Post Pure periods
are shown in a compressed fashion to show the ignition
process in detail.
1. Boiler receives a demand either CH or DHW.
2. Blower ramps up to ignition high speed to prove air
flow.
3. Blower ramps down to ignition speed and holds for
Pre-purge period of 30 seconds.
4. Spark is initiated 1 second before gas valve.
5. Gas valve opens.
6. Gas valve remains open for flame proving period.
If no flame is detected, the gas valve closes and the
blower moves to Post-purge.
7. If flame is detected, the boiler will begin to modulate
to maintain setpoint until the demand is removed.
8. Once demand is removed, gas valve closes and
blower moves to Post-purge for 30 seconds.
9. After Post-purge, blower shuts down and awaits next
demand.
O. ADDITIONAL SAFETY FUNCTIONS
1.
Ignition Failure Protection
: The Series PFC™ control
allows for 1 failed ignition attempts before the control
goes into a lockout state showing “IGNITION ERROR
(1)”. Manual control reset is required, this lockout
can be reset by pressing and holding the reset button,
left most button, on the display. The control can also
be manually reset by pressing the “
RESET
” button
below the control state LED on the main control
board.
2.
Flame Failure Protection
: The Series PFC™ control
monitors for flame failure during a demand. If the
flame signal is lost more than 3 times during a single
demand the control will go into a lockout state
showing “TOO MANY FLAME LOSS (22)”. Manual
control reset is required, this lockout can be reset
by pressing the manual “
RESET
” button below the
control state LED on the main control board.
3.
Flue Temperature Protection
: Series PFC™ control
monitors the flue temperature sensor for high
temperatures. If the flue temperature approaches
190°F (88°C), the boiler will begin to modulate input
down regardless of setpoint or demand. If the flue
temperature reaches 190°F (89°C) the boiler will
shut down and run the blower for 5 minutes before
re-ignition.
4.
Flame Recovery
: The Series PFC™ control actively
monitors the ionization current though the flame
sensor. If Flame Signal drops to below 1.0 μA, the
control will increase the minimum fan speed in order
to attempt to maintain flame signal. If this fails, the
control will enter a lockput state. If at any point the
demand is met the control will reset the minimum fan
speed to default.
5.
Stayburn and Startburn Temperatures
: When
the supply temperature of the boiler exceeds the
maximum boiler setpoint due to the off hysteresis of
9°F and a demand is still present, the Series PFC™
control allows the unit to run at 1% input until the
Stayburn temperature is reached at 193°F (88°F). The
boiler will always shutdown at this temperature and
will never exceed it. The Series PFC™ is not designed
to run beyond this temperature. Steps should be taken
to improve the system to lower the required setpoint
if the Stayburn Temperature is ever reached. The
boiler will not re-ignite until the Startburn temperature
is reached below the setpoint. The Startburn
Temperature is 185°F (85°C). If the Stayburn
temperature is exceed a “MAX TEMP ERROR (15)”
will be produced.
6.
Frost Protection
: The Series PFC™ control monitors
the unit for potential freeze situation which would
cause damage to the internal piping of the unit. If the
water temperature inside the unit falls below 50°F
(10°C) the boiler pump will start. If the temperature
continues to fall the burner will ignite to and heat the
unit at minimum input until the supply temperature
reaches 59°F (15°C).
7.
Filling Protection (Optional)
: The Series PFC™ control
comes equipped with connections to install a pressure
switch to monitor system pressure. This connection
has a jumper installed by default across dry contacts.
DO NOT USE a high voltage contact for this purpose.
8.
De-air
: Upon boiler power initiation, the Series PFC™
control will enter a de-air state during which it will
purge any air remaining in the system by cycling the
pump on and off and changing the position of the
switching valve. This period lasts for 4 minutes. It
can be canceled by holding buttons L2 and R2 for 3
seconds simultaneously.
9.
Low Water Cut Off
: The Series PFC™ control comes
equipped with a probe style LWCO located on the
supply pipe. The control will monitor for low water
conditions. If such a condition occurs the control will
go into a lockout state and must be manually reset.
10.
Flue Pressure and Block Condensate Switch
: The
Series PFC™ control monitors a pressure switch
that will enter the boiler into a blocking state. This
switch will display “BLOCKED CONDENSATE FLUE
PRESSURE ERROR (156)”. Clearing of the flue or
condensate line will automatically clear this error.
8. Once demand is removed, gas valve closes and
blower moves to Post-purge for 30 seconds.
9. After Post-purge, blower shuts down and awaits next
demand.
P. MULTIPLE BOILERS
1. Multiple Boiler Wiring: The connection from the managing
boiler to the dependent boilers should be in parallel.
a. Figures 8.9 and 8.10 shows the wiring configurations.
This method creates independent connections to each
dependent boiler to reduce risk of communication loss
between boilers.
b. Each boiler controls its own “General” pump that
operates any time that boiler is operating. It is extremely
important to have water flow through the boiler during
burner operation.
c. All external inputs (Outdoor Temperature Sensor, DHW
Tank Temperature Sensor and System Sensor) must be
