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Heating Operation and Adjustments
A−Heating Sequence of Operation
1− When the thermostat calls for heat, the combustion
air blower starts immediately.
2− The combustion air switch checks for proper blower
operation before allowing power to the ignition
controller. This switch is factory set and no
adjustment is necessary.
3− After a pre−purge of 45 seconds, the spark ignitor is
energized, and the solenoid valve opens in the gas
valve.
4− The spark then ignites the gas, the ignition sensor
proves the flame and the combustion process
continues.
5− In the event that the flame is not detected after the
first trial for ignition, the controller will repeat steps 3
and 4 up to two more times (depending upon
controller model) before locking out.
6− For troubleshooting purposes, an ignition attempt
after lock out may be re−established manually. Move
thermostat HOFF" and return thermostat switch to
HHEAT" position.
B−Limit Control
Limit controls are factory set and not adjustable.
Two primary limits are located on the division panel
between the return and supply sections on high heat
units. One primary limit is located on the division panel on
standard heat units.
A secondary limit is located on the blower transition in
both standard and high heat units.
C−Heating Adjustment
1− Main burners are factory adjusted for proper flame.
Air shutters are provided for localized areas if
necessary.
2− Burner flames may be observed through the
inspection port in the access panel. Always operate
the unit with the access panel in place.
WARNING
Danger of explosion. Can cause injury or
death. Do not overtighten main burner
mounting screws. Snug tighten only.
3− The gap on the flame sensing electrode should be
between 3/32" and 5/32" (0.094 − 0.156 mm).
Remove right burner by removing screw and sliding
the burner off the orifice. The carry over slot on all
burners is 1/8" (.125 mm) and it must be maintained.
Clean the carry over slot using a strip of 16 gauge
steel. Check gap with 1/8" (.125mm) twist drill.
Replace all burners using mounting screws.
4− Gas manifold pressure should be set at 3.5" w.c. for
natural gas units and 10.5" w.c. for LP gas units.
Units must be derated when installed at altitudes
above 4500 feet (610 m) above sea level. At
altitudes above 4500 feet (610 m), units must be
derated to match the gas manifold pressures
shown in table 16.
NOTE0This is the only permissible derate for these units.
TABLE 16
Altitude − ft (m)
Gas Manifold Pressure−in. w.g. (kPa)
Altitude − ft. (m)
Natural
LP (Propane)
4501−5500 (1372−1676)
3.4 (0.85)
10.2 (2.54)
5501−6500 (1676−1981)
3.3 (0.82)
9.8 (2.44)
6501−7500 (1981−2286)
3.2 (0.80)
9.5 (2.36)
