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MODU-FIRE® FORCED DRAFT
Gas-Fired Boiler Installation
The boiler is furnished with a low gas pressure
switch. The operation of this switch must be
checked by slowly closing the main gas cock while
the burner is operating. The switch should shut
down the main burner. When the gas pressure
switch opens, the "Gas Press." indicator will light.
Upon reopening the main gas cock, the "Gas Press."
indicator should remain on until the low gas pres-
sure switch is manually reset.
3.11.5 Test of High Gas Pressure Switch
The boiler is furnished with a high gas pressure
switch. The operation of this switch must be
checked by closing the downstream main gas cock,
and starting the boiler. Once the trial for ignition
period is reached, the main gas valve will open,
pressurizing the line. This will trip the high gas
pressure switch.
The high gas pressure switch must be manually reset
after it trips.
3.12
INITIAL ADJUSTMENTS
3.12.1 Configuring the Temperature Control
The boiler is equipped with a modulating tempera-
ture control to maintain the desired outlet water
temperature. This control has various modes of op-
eration which are listed below.
Definitions:
The following items are common to Modes 1 thru 5.
They are not required for Mode 6 – the mode for
external boiler control.
MODE: Operating mode of the boiler.
BOIL TARGET: Target temperature that the
boiler is trying to maintain.
BOIL MAX: Highest outlet water tempera-
ture that the control is allowed
to use as a target temperature.
BOIL MIN: Lowest outlet water tempera-
ture that the control is allowed
to use as a target temperature.
FIRE DELAY: Factory Set (Low fire
hold)
BOIL MASS: Factory Set DO NOT
MODIFY THIS ITEM
DIFF: The operating differential
of the boiler. The boiler
outlet water temperature is
allowed to rise above the
BOIL TARGET tempera-
ture by 1/2 of this differen-
tial before the boiler shuts
off.
MOTOR SPEED: Factory Set DO NOT
MODIFY THIS ITEM
START Modulation: Factory Set DO NOT
MODIFY THIS ITEM
MIN Modulation: Factory Set DO NOT
MODIFY THIS ITEM
PUMP DLY: Sets the operating time of
the pump once the boiler is
turned off.
UNITS: Selects the temperature
units to be displayed (
o
F or
o
C).
For example, if the boiler target temperature is set to
160°F and the differential is set to 10°F, on tem-
perature rise, the boiler will shut off at 165
o
F. Once
the boiler shuts off, it will not come on again until
the temperature falls to 155
o
F.
Operating Modes:
Mode 1 – setpoint operation using parallel pip-
ing. The boiler outlet water temperature is con-
trolled to the boiler target setpoint.
Mode 2 – setpoint operation using pri-
mary/secondary piping. The control modulates
the boiler to satisfy a remote header sensor. The
boiler is turned off based on boiler max and
boiler differential.
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