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3. Flame Rollout Switches (Figure 11)
Flame rollout switch S47 is a high temperature limit located
inside the burner box. Each furnace is equipped with two
identical switches. The limit is a N.C. SPST manual-reset
limit connected in series with the primary limit S10. When
S47 senses rollout, the circuit breaks and the integrated
control immediately stops ignition and closes the gas valve.
If unit is running and flame rollout is detected, the gas valve
will close and integrated control will be disabled. Rollout
can be caused by a blocked heat exchanger, flue or lack of
combustion air. The switch is factory set to trip (open) at
210°F and cannot be adjusted. The switch can be manually
reset. To manually reset a tripped switch, push the reset but-
ton located on the center of the switch.
4. Burners (Figure 11)
All units use inshot burners. Burners are factory set and re-
quire no adjustment. Always operate the unit with the burner
box front panel in place. Each burner uses an orifice (see table
29 for orifice size) that is precisely matched to the burner input.
Burners can be removed as a one piece assembly for service.
If burner assembly has been removed, it is critical to align cen-
ter of each burner to the center of the clamshell when re−instal-
ling. See more detail in Section VII− MAINTENANCE..
5. Duralock Plus
Heat Exchanger (Figure 12)
SLP98UHV units use an aluminized steel primary and
stainless steel secondary heat exchanger assembly.
Heat is transferred to the air stream from all surfaces of
the heat exchanger. The shape of the heat exchanger en-
sures maximum efficiency.
The combustion air inducer pulls fresh air through the burn-
er box. This air is mixed with gas in the burners. The gas / air
mixture is then burned at the entrance of each clamshell.
Combustion gases are then pulled through the primary and
secondary heat exchangers and exhausted out the exhaust
vent pipe.
FIGURE 11
Burner Box Assembly
burner assembly
rollout switch
ignitor
flame sensor
burner box front cover
(remove screw to open cover)
sight glass
intake air collar
