46
FURNACE COMPONENTS
The descriptions below are various functional components that affect the operation and shutting down of this furnace.
Some of these components and their locations are shown in
. If any component of the furnace must be
replaced, use only factory authorized replacement parts specified in the Replacement Parts List provided online.
Blower Limit Switch -
The Blower switch prevents furnace operation when blower is not operational.
Condensate Drain Switch -
The Condensate Drain Switch will shut down the furnace if the condensate drain from
the Collector Pan becomes clogged.
Flame Sensor: The flame sensor verifies when a flame has carried over from the igniter to the opposite end burner.
If no flame is detected, the furnace will shut down within 4 seconds.
Flame Roll-Out Switch -
The flame roll-out switch verifies that the burner flames are drawn into the heat exchanger
tubes. If the burner flames are not properly drawn into the heat exchanger, the flame roll-out switch will close the
gas valve and initiate the shutdown cycle.
Gas Valve -
The gas valve controls the flow of gas to the burners. When the gas valve is energized it automatically
opens and regulates the gas pressure in the manifold.
Inducer Assembly -
The inducer assembly vents products of combustion to the outside.
Pressure Switch -
The pressure switch verifies that the inducer is drawing the combustion gases through the heat
exchanger. If the flame is not properly drawn into the heat exchanger tube, the rollout switch or the flame sensor
will shut the furnace down.
Supply Air Limit Switch -
The supply air limit switch prevents the air temperature leaving the furnace from exceeding
the maximum allowable outlet air temperature.
Figure 46
M4RC Series Upflow Gas Furnace
Figure 46.
M4 Series Component Locations
Blower
Assembly
Blower Door
Switch
Burner
Assembly
Control Board
Finish
Flange
Flame
Sensor
Gas Manifold
Gas Valve
Igniter
Inducer Assembly
Main Air Limit Switch
Pressure Switch
(Inducer)
Pressure Switch - Condensate
(‘B’, ‘C’, & ‘D’ cabinets only)
Roll-Out
Switch
Transformer
Vent Limit Switch
Finish
Flange
Blower
Assembly
Blower Door Switch
(behind blower panel)
Burner
Assembly
Flame
Sensor
Gas Manifold
Gas Valve
Igniter
Inducer Assembly
Pressure Switch
Vent Limit Switch
Control Board
Main Air Limit Switch
Transformer
Roll-Out
Switch
M4RL Series Downflow Gas Furnace
Summary of Contents for M4RC-072D-35C
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