3
 
FURNACE COMPONENTS
 
Combustion-air intake connection to ensure 
contaminant-free air (right or left side).
Burner sight glass for viewing burner flame.
Burner assembly (inside). Operates with energy-
saving inshot burners and hot surface ignitor for safe, 
dependable heating.
Redundant gas valve. Safe, efficient. Features 1 gas 
control with 2 internal shut-off valves.
Vent outlet. Uses PVC pipe to carry vent gases from 
the furnace’s combustion system (right or left side).
Inducer motor. Pulls hot flue gases through the heat 
exchangers, maintaining negative pressure for added 
safety.
Blower access panel safety interlock switch.
Air filter and retainer.
Condensate drain connection. Collects moisture 
condensed from burned gases for disposal into home 
drain system.
Heavy-duty blower. Circulates air across the heat 
exchangers to transfer heat into the home.
Secondary condensing heat exchanger (inside). 
Wrings out more heat through condensation. 
Constructed with Polypropylene-laminated steel to 
ensure durability.
Primary serpentine heat exchanger (inside). 
Stretches fuel dollars with the S-shaped heat-flow 
design. Solid construction of corrosion-resistant
aluminized steel means reliability.
Control center.
3-amp fuse provides electrical and component 
protection.
Light emitting diode (LED) on control center. Code 
lights are for diagnosing furnace operation and 
service requirements.
Pressure switch(s) ensure adequate flow of flue
 products through furnace and out vent system.
Rollout switch (manual reset) to prevent 
overtemperature.
Junction box for 115-v electrical power supply.
Transformer (24v) behind control center provides 
low-voltage power to furnace control center and
thermostat.
Limit switch (manual reset) on 58MVP only.