Page 27
3 - Clock gas meter to ensure that the unit is operating
at the specified firing rate. Check the supply
pressure and the manifold pressure. On two-stage
gas furnaces check the manifold pressure on high
fire and low fire. If manifold pressure adjustment is
necessary, consult the Service Literature for unit
specific information on adjusting gas pressure.
Not all gas valves are adjustable. Verify correct
temperature rise.
Cleaning the Heat Exchanger and Burners
NOTE -
Use papers or protective covering in front of the
furnace during cleaning.
1 -
Turn off both electrical and gas power supplies to
furnace.
2 - Remove flue pipe and top cap (some applications
top cap can remain) from the unit.
3 - Label the wires from gas valve, rollout switches,
primary limit switch and make-up box then
disconnect them.
4 - Remove the screws that secure the combustion air
inducer/ pressure switch assembly to the collector
box. Carefully remove the combustion air inducer
to avoid damaging blower gasket. If gasket is
damaged, it must be replaced to prevent leakage.
5 - Remove the collector box located behind the
combustion air inducer. Be careful with the collector
box gasket. If the gasket is damaged, it must be
replaced to prevent leakage.
6 - Disconnect gas supply piping. Remove the four
screws securing the burner manifold assembly to
the vestibule panel and remove the assembly from
the unit.
BURNER, COMBUSTION AIR INDUCER ASSEMBLY
&
HEAT EXCHANGER REMOVAL
Heat Exchanger
Gasket
Collector Box
Orifice Plate
Flue Transition
Pressure Switch
Combustion Air Inducer
Manifold And Gas Valve
Retention Rings
Cross Over
Ignitor
Flame
Sensor
Rollout Switches
FIGURE 25
