FURNACECOMPONENTS
HEAT EXCHANGER SUB-SYSTEM
Primary Heat Exchanger
The 90 Plus gas furnace heat
exchanger is a tubular type with one
burner per tube. A steel turbulator is
inside the end of each primary heat
exchanger tube to enhance heat
transfer before entering the
secondary heat exchanger.
The tubes terminate in a transition
box which connects to the secondary
heat exchanger. The primary heat
exchanger tubes are type 409
stainless or aluminized steel
("J" series). The transition box is
aluminized 409 stainless steel.
Secondary Heat Exchanger
The secondary heat exchanger is a
single pass coil using 3/8 inch
diameter 29-4C stainless steel tubes
each having internal "turbulator"
strips. These stainless steel tubes
are expanded into aluminum fins to
enhance heat transfer. There are
twelve different coil assemblies for
upflow and downflow models varying
in width and number of tubes. Flue
gas condensation actually occurs in
the secondary heat exchanger. The
latent heat produced in combustion
is captured here.
Both primary and secondary heat
exchangers come as one piece that
mount together on the center panel.
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FIGURE4
INSHOT BURNER
FIGURE3
HEAT EXCHANGER
COMBUSTION SUB-SYSTEM
Burners
Each furnace uses from three to
eight inshot burners. They are made
of aluminized steel with internal
precision main and crossover porting
to provide flame retention, proper
carryover, and burner stability. There
are no primary or secondary air
adjustments. The burners slip over
the orifice spuds and are secured in
place with screws. Each burner tube
fires at 15,000 BTUH input at the
rated manifold gas pressure.
FIGURES
Induced Draft Blower (IDB)
All models use a PSC induced draft
blower (IDB) with a thermoplastic
body to pull combustion gases
through the heat exchanger. It uses
sleeve bearings and is permanently
lubricated with a synthetic lubricant.
The blower withstands 250°
temperatures, and is very quiet by
virtue of its final balancing operation.
The IDB uses a 4.0 mfd, 370 volt
run capacitor. The capacitor mounts
to the side of the main blower
housing.
INDUCED DRAFT BLOWER
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