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9
System Start-up
2. Test the flow switch by disabling the primary
loop circulator. The boiler must not start if flow
is not present.
3. Test any other external limits or other controls
in accordance with the manufacturer's
instructions.
Q. Check Thermostat Operation
Verify that the boiler starts and stops in response
to calls for heat from the heating thermostat and
indirect water heater thermostat. Make sure that
the appropriate circulators also start and stop in
response to the thermostats.
R. Adjust Supply Water Temperature
As shipped, the heating set point supply
temperature is set to 180°F (82.2°C) and, indirect
water heater set point supply temperature is set
to 170°F (76.7°C). If necessary, adjust these to
the appropriate settings for the type of system to
which this boiler is connected. See Section 10
"Operation" (Central Heat parameter table) of this
manual for information on how to adjust supply
setpoint.
S. Adjust Thermostats
Adjust the heating and indirect water heater
thermostats to their final set points.
T. Field Conversion From Natural Gas to
LP Gas (Propane)
Apex models APX425C and APX525C are factory
shipped as natural gas builds and can be field
converted to LP gas. Follow steps below for field
conversion from natural gas to LP Gas.
Models APX625C, APX725C and APX825C are
factory shipped as either natural gas build or LP
gas build. Field conversions of models APX625C,
APX725C and APX825C are not permitted.
1. Conversion of Apex models APX425C
and APX525C from one fuel to another is
accomplished using the throttle screw on the
gas valve. Figure 9-5 "Gas Valve Detail" shows
the location of the throttle screw on the valve.
Locate the throttle screw on the boiler being
converted.
106308-05 - 3/23
(continued)
APEX
Installation, Operating, & Service Instructions
!
WARNING
Explosion Hazard. Asphyxiation Hazard.
This conversion should be performed by a
qualified service agency in accordance with the
manufacturer's instructions and all applicable
codes and requirements of the authority having
jurisdiction. If the information in these instructions
is not followed exactly, a fire, an explosion or
production of carbon monoxide may result causing
property damage, personal injury, or death. The
qualified service agency is responsible for proper
conversion of these boilers. The conversion is not
proper and complete until the operation of the
converted appliance is checked as specified in
this manual.
2. If conversion is being made on a new
installation, install the boiler in accordance
with the installation instructions supplied
with the boiler. If an installed boiler is being
converted, connect the new gas supply to the
boiler, check for gas leaks, and purge the gas
line up to the boiler in accordance with the
National Fuel Gas Code, ANSI Z223.1/NFPA
54 and/or Natural Gas and Propane Installation
Code, CAN/CSA B149.1 or the requirements of
the authority having jurisdiction.
3. Before attempting to start the boiler, make the
number of turns to the throttle screw called for
in Table 10-9.
4. Start the boiler using operating instructions
in Figure 9-1. After the boiler is powered
up with a call for heat, the boiler should go
through the sequence of operation shown in
Table 10-11. Even if the gas line has been
completely purged of air, it may take several
tries for ignition before a flame is established.
If more than 2 tries for ignition are needed, it
will be necessary to press the reset button to
restart the boiler. If boiler does not light, turn
the throttle screw counter-clockwise in 1/4 turn
increments, allowing the boiler to make at least
three tries for ignition at each setting, until the
boiler lights.
Table 9-6: Approximate Clockwise Throttle
Screw Turns for LP Gas (Propane)
Conversion
Boiler Model
APX425C
APX525C
APX625C
APX725C
APX825C
Approximate
Throttle Screw Turns
2¾
3
N/A - Factory LP Builds
73
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